Threats to and protection of coral reefs

Transcription

Antonius
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Lecture (SS 2000)
Threats to and protection of coral reefs
(gefährdung und schutz von korallenriffen)
VO 859403
given by
dr. Arnfried Antonius
University of Vienna
(script compiled by P.Madl)
Part I Definition…………………………………………..
Reef building organisms.……...…………………...
Characteristics of organic reefs…………………….
Structure of coral reefs……..…………...………….
Constructive Components of Reef…………………
Coral reef development…..………………………..
Taxonomy of cnidaria…..……………………….…
Development of coelenterata..……………….
Acnidaria (ctenophora).………………………
Cnidaria………………………………………
Morphology of cnidaria………………………
Alternation of generation in cnidaria…………
class Scyphozoa..……….....…….…………...
order Stauromedusae…………………….
order Coronatae………………………….
order Semaeostomae………………….…
order Rhizostomae…………………….....
Order Cubozoa…………………….…….
class Hydrozoa…………..………………......
order Trachylina and Siphonophora……..
order Hydroida (Athecata and Thecata)…
class Hydrocorallina……..……..…………...
order Milleporina…………………...……
order Stylasterina…………………...……
class Anthozoa………………………………
subclass Octocorallia………..……………
order Telestacea…………………….……
order Alcyonacea……………………..….
order Stolonifera………………………....
order Gorgonaceae……………………....
order Pennatulacea………………………
order Helioporaceae……………….…….
subclass Hexacorallia………..………..…..
order Actinaria…………………………...
order Antipatharia.………………………
order Ceriantharia.……………….………
order Corallimorpharia.…………….……
order Zoanthidae.……………….……….
order Scleractinia (madreporina).………..
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Part II Scleractinian coral reproduction and growth……...
Sexual reproduct. (brooders, broadcasters)…..
Asexual reproduction……………………...…
Anthocaulus, anthocyathus in Fungiidae.……
Growth rates………………………………….
Morphology of scleractinian corals.….………...….
Corallite structure and their elements.……….
Colony growth , forms, and shapes…………..
Physiology of scleractinian corals...………...…......
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Part III Reef zonation…………………………………….
Deep fore reef, ….……………….………
Reef slope, reef front, reef terrace, ……..
Fore reef, reef crest……………………...
Reef flat, living coral sub-zone...………..
Coral sub zone, lagoon; cay, shore………
Reef Communities……………………………….
Protozoa and the food web………………
The flora of reefs………………...…………...
Chlorophyta..…………………………….
Phaeophyta………………………………
Rhodophyta……………………………...
Cyanobacteria……………………………
Angiospermia……………………………
The fauna of reefs………..……….….……….
Porifera…………………………………..
Mollusca…………………………………
Annelida…………………………………
Arthropoda………………………………
Echinodermata…………………………...
Other reeffauna…………………………..
Chordata……………………..……………….
Tunicates………………………………...
Chondrichthyes………………………….
Osteichthyes……………………………..
Fish in the reef ecosystem…..…………...
Reptiles…………………………………..
Mammalia……………………………….
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Part IV Environmental parameters……………………….
Reef degradation…………………………...….…
Destruction of the reef - abiotic factors....….……
Chemical factors…………………………
Physical factors………………………….
Destruction of the reef - biotic factors….….……
Coral diseases……………………………………
Disease working without a pathogen………...
TBL, WBD…………………………..…..
Disease working witht a pathogen…………...
BBD;
RBD, BOC, BAB, BI…….……………...
FI, LOD, YBD, DSD…..………………..
SDR, SEB, PEY………………………....
Diseases involving a combination……………
WS……………………………………….
Mutations and other tissue abnormalities..…..
Hyperplasia, neoplasia…………………..
Future outlook……………………………………
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Part V References on the web.…………………..……… 67
http://www.sbg.ac.at/ipk/avstudio/pierofun/funpage.htm
biophysics.sbg.ac.at/home.htm
Antonius
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PART I - Definitions:
Riff1: ein riff ist eine massgeblich von lebenden organismen aufgebaute, meist bankförmige struktur, die vom
meeresboden bis zur wasser-oberfläche reicht. Es kann die fysikalischen und ökologischen eigenheiten
ihrer umgebung beeinflussen. Die konsistenz ist fest, um den kräften im wasser zu widerstehen und
bildet somit einen gegliederten raum für angepasste bewohner (Schuhmacher 1976).
riffe
anorganische riffe
organische riffe
andere organismen
(siehe “Biologie Rezenter
Riffe“ - Velimrov2)
korallenriffe
Riffbildende organismen:
Algen, insbesondere kalkproduzierende rotalgen der familie Corallinacea tragen massgeblich zum aufbau von
korallenriffen bei.
Fädige blaualgen, bilden polster die in weiterer folge durch sedimentation “verkleben“ und letzendlich
versteinern; anhäufungen solcher blöcke bilden riffe;
seit dem präkambrium sind die cyanobakterien als baumeister der sogenannten Stromatolithen-riffe
bekannt, die in heutiger form in der Shark Bay, vor der westaustralischen küste aktiv tätig sind.
Seegräser in verbindung mit riffen ist eher als eine missbräuchliche begriffsverwendung für sogenannte
“sedimentfallen” zu verstehen (lt. Moliet und Picard); die sedimentverfestigung wird durch das
wurzelwerk des seegrases gefördert - sind daher erst durch die einwirkung mehrerer faktoren in der lage
riffähnliche gebilde hervorzubringen; bislang wurden derartige verfestigungen mit 10m mächtigkeit
vermessen; da algen und seegräser in den tropen immer anzutreffen sind vermutet man daher nicht zu
unrecht dass sandstein-bänke aus seegras-beständen hervorgegangen sein müssen.
Polychaeten-riffe3), vertreter einiger gattungen (z.b. Sabellaria und Phragmatopoma) bilden mächtige
ansammlungen, welche durchaus die bezeichnung "riff" verdienen. So bildet Phragmatopoma lapidosa
in der brandungszone der ostküste Florida’s bis zu 1m hohe riffe, welche sich mit unterbrechungen über
eine länge von mehr als 300km erstrecken. Deren wohnröhren sind mit sand ausgekleidet die durch
bioaktivitat der würmer verkrusten. Unter den Sabellariidae sind weiters auch jene vertreter der gattung
Sabellarida florensis und S.vulgaris als riffbauer bekannt.
Serpulliden-riffe4, zu den riffbildenden würmern zählen auch die borstenwürmer der familie Serpulidae; treten
sie in massen auf, so können ihre röhren zu einer kompakten kalkstruktur verbacken. Spirobranchus
giganteus ist in massen vor Texas und Florida zu finden (siehe auch fig.1).
Gastropoden (vermitiden)-riffe4, rezente und fossile riffe dieser art finden sich nicht nur vor Florida’s küste,
sondern auch im östlichen Mittelmeer; Vermetus nigricans baut riffe indem die freischwimmenden
larven sich am hartsubstrat festsetzen und gewundene kalkröhren anlegen die sie mit benachbarten
individuen verzementieren (siehe auch fig.1) .
Bivalvia, wie z.b. austern (Ostrea edulis) und miesmuscheln (Mytilus edulis) bilden ebenso grossflächige
muschelbänke, sind aber durchwegs auf gemässigte breiten beschränkt.
Korallen, zu den wichtigste riffbildnern zählen jene zu den nesseltieren (Cnidaria) gehörenden steinkorallen
(Madreporaria), und andere hermatypische (riffbildendene) korallen, wie z.b. feuerkorallen (familie
Milleporidae) als auch hornkorallen (familie Gorgoniidae) sowie weitere vertreter anderer familien.
Mithilfe der kalksynthese scheidet der korallenpolypen kalk ab. Die zur kalkbildung nötigen kalziumionen (Ca2+) und kohlendioxid (CO2) werden im meereswasser oder im korallenpolypen, von den skelettaufbauenden zellen zur verfügung gestellt. Daraus wird kalziumkarbonat (CaCO3) gebildet. Dies kann
jedoch nur in gewissen massen produziert werden, da das produkt durch massenwirkungs-gesetze
teilweise wieder in lösung geht. Wird aus dem reaktionssystem kohlensäure (HCO3-) entzogen, kann
vermehrt kalk synthetisiert werden. Die zooxanthellen übernehmen diese funktion, sie “saugen” CO2
vom stoffwechsel der korallen und verwenden es für ihre fotosynthese. Mit hilfe der zooxanthellen
können korallen ihre kalkproduktion um ein vielfaches erhöhen (see p22 figure 41a).
Kurz einige begriffe aus der paläontologie die in der riffbildung eine rolle spielen:
BIOHERM = a mound, dome, or reef-like mass of rock that is composed almost exclusively of the remains of
sedentary marine organisms and is embedded in rock of different physical character (riffartig die
hügelförmig oder linsenförmig ist - streng organisch entstanden; durch einlagerung organischer
strukturen ins gestein).
BIOSTROM = refers to a flat bed of often in-situ skeletal organisms without significant relief; riffbildung die
ausschliesslich durch sedimentäre organismen herrührt; streng genommen handelt es sich dabei
um eine geschichtete struktur (z.b. durch muscheln bewerkstelligt) die nicht hügel- oder
linsenförmig aufgeschichtet ist.
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The map (adapted from Jaap &Hallock, 1990)
shows the different kinds of reefs in Florida and
their locations. It must be noted that the habitat
distribution is very patchy in each area. In
southwestern Florida, the Vermetids are mainly
located in the Ten Thousand Islands area but
also extend intermittently along the western
coast of Florida as far as Sarasota. However,
they are not found in Florida Bay or the Keys,
but a small colony has been reported on the old
coaling piers at Fort Jefferson in the Dry
Tortugas. Some researchers have reported in the
literature that they consider the species that is
found in the “Ten Thousand Islands” area are
extinct, as the reefs were formed during the last
interglacial period that drowned the beach
ridges that make up the present-day islands.
Foraminiferen-riffe5 sind überwiegend azooxanthellaten und daher auf tiefere gewässer
beschränkt; lediglich Marginopora vertebralis
ist als eine der wenigen vertreter auch in der
eufotischen zone zu finden und wird durch die
aktive
mitwirkung
der
zooxanthellaten
besonders gross und kann somit regelrechte
foraminiferen-bänke aufbauen.
Fig. 2 Marginopora vertebralis
Fig. 1 Serpulid- and Vermitid-reefs4
Ahermatypische
korallen
(frei
von
zooxanthellaten), beispielhaft einige vertreter:
Cladocora cespitosa6, eine im mittelmeer vertretene art baut monospezifische bänke auf.
• Lophelia pertusa7, ist ein biohermer vetreter
und bildet bestände die einige 100m lang
werden können; ist in allen ozeanen vetreten
und geht in tiefen bis zu 100m.
• Oculina varicosa8, kann mit oder ohne
zooxanthellae ihr auslangen finden; unter
mitwirkung der zooxanthellen ist sie am riffaufbau beteiligt, bei abwesenheit ist sie
Fig.3a,Cladocora
meist in einigen 100m tiefe als buschigcespitosa
verzweigte “dickichte” in atlantischen
gewässern vorzufinden.
ahermatypische korallenAlle andere tiefsee-korallen (bis in 1000m tiefe) riff-strukturen:
sind ahermatypisch (azooxanthellat).
Fig.3c Oculina varicosa
Charakteristika von organischen riffen;
• gebaut / gebildet von lebenden organismen;
• ständige selbsterneuerung (“selbstreparatur” - see also p55, reef degrdation);
• errichten vorwiegend bankförmige strukturen;
• die vom meeresgrund bis an die wasser-oberfläche reichen können;
• und hinreichend fest sind um der wellen/brandungs-aktivität widerstehen zu
können.
Fig.3b Lophelia pertusa
Fig.4 Tridacna gigas
Lediglich die korallenriffe sind gross und fest genug um aus ozeanischer sicht den lebensraum zu
beeinflussen indem sie durch aminosäure-produktion (biochemisch) und absorption von nitraten, fosfaten
(chemisch) die salinität vorort beeinflussen; durch deren enormen ausmasse beinflussen derlei riffstrukturen
die lichtverteilung am riffkörper, wogengang, wasserströmungen, wassertemperatur und somit indirekt den
pO2-gehalt des wassers, (allesamt fysikalisch); daraus resultiert eine ökologische zonierung die schutz für
jungtiere, unterschlupf und nischen für adulttiere bzw. generell neue lebensräume auch für höhlen- und
lochbewohner schafft (see also p23, reef zonation). Riffe sind durchwegs auf nährstoff-arme, kristallklare
gewässer beschränkt, und produzieren doch soviel an mehrbedarf um auch andere lebewesen mehr oder
weniger direkt zu versorgen.
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In vielen bereichen der erde kommen den korallenriffen eine weitere funktion zu - durch die zerstörung
vieler saum- und konturriffe geht die wellenbrechende funktion eines gesunden riffkörpers verloren; in folge
dessen kommt es zu verstärkter küstenerosion. In sofern beeinflusst ein degradiertes riff auch das
küstennahe ökosystem an land. Ein mangrovengürtel kann nur in beruhigten küstennahen gewässern
spriessen - ein vorgelagertes riff ohne wellenbrechende funktion setzt die küstenvegetation einer vermehrten
brandung aus, wodurch es über kurz oder lang zum rückzug des mangrovenbestandes kommt (see p28, reef
zonation).
Aufbau von korallenriffen: steinkorallen sind nur ein teil der vorkommenden bausteine;
• in den tropen kommt vieler orts auch der Tridacna gigas9 eine tragende rolle zu;
• das füllmaterial ist im wesentlichen kalksand (aus erodiertem bzw; abgestorbenem, biogenem ursprung, wie
z.b. schwamm-spikel, mollusken, echinodermaten, korallensubstanz, etc.); papageienfische (Sparidae sp.)
weiden korallen der zooxanthellen wegen ab; drückerfische ernähren sich von seeigeln, krabben, muscheln
und scheiden gleichfalls das zermahlte kalksubstrat wieder aus; bohrschwämme und seeigel tragen
wesentlich zum substratabbau am riffkörper bei (see p57, bioerosion);
• als bindematerial (kleber) sind inkrustierende corallinacea (kalk-rotalgen, wie Porolithon, Melobesia) tätig;
aber auch foraminiferen (Hamotrema rubra) und bryozoen erfüllen diese funktion;
Constructive components of a reef (see also p29 or Velimirov p16 .... /riffe-bv.pdf)
1. Foundation: sedentary organisms (diatomea, ciliates, foraminifers, corallinaceae, Montipora, Porites, etc)
form the solid and stable foundation on which the reef system can flourish. A principal requirement for a
reef is the ability to maintain a strong substrate or base on which subsequent growth can develop. In many
cases, after major tropical storm events (cyclones = typhoons = hurricanes), the remainder of the reef may
comprise of only this solid foundation.
• Growth of rigid, interlocking structure.
• Skeletal structures often remain in growth position.
• Only a surfacial veneer is alive.
2. Framework Components: much like the steel girder system of a skyscraper, the framework of the reef
allows for rapid upward growth of the reef into shallower water. A common example of the type of coral
that fills this role is A. palmata (Caribbean elkhorn coral). Note that the shape that this coral develops is in
direct response to the nature of the energy across the reef (see p. 26, fore reef).
• phylum Cnidaria / class Anthozoa / subclass Zoantharia / order Scleractinia: stony corals;
class Hydrozoa / order Milleporina: hydrocorals;
• phylum Porifera (sponges) / class Sclerosponges or coralline sponges.
3. Encrusting Components: secrete calcareous, encrusting cement to add additional strength to the reef
structure. Upon this framework, corals, sponges, hydrozoans and bryozoan coat the surfaces. If one were to
peer into the crack and crevices amongst the framework corals, new and diverse worlds of organisms occupy
this niche (or space) with the environment. As we move up into the highest energy parts of the reefs we find
that this region is dominated by encrusting growth forms.
Although technically not encrusting, the
hydrozoan Millipora (firecoral) forms
complex honeycomb like structures which
are capable of withstanding extreme
energies associated with the rim or crest of
the reef. At this site, breaking ocean waves
produce the highest energies associated with
the reef system.
• phylum Rhodophyta: red algae or
crustose coralline algae;
• phylum
Foraminifera:
encrusting
foraminifers such as Homotrema;
• phylum Bryozoa;
• phylum Annelida: serpulid worms;
• phylum Mollusca: vermetid gastropods. Fig. 5a dynamik der faciesbereiche eines karibbischen riffes
4. Bafflers and Binders for soft tissue
intergrowth; flexible seafans, grasses, seawhips, and algae locally slow the speed of moving currents above
the reef. As these waters slow in speed, material carried in suspension settle out upon the reef surface
(sediment trap). This sedimentation leads to the upward accretion or growth of the reef system.
• phylum Porifera: encrusting, massive forms
• phylum Coelenterata / subphylum Cnidaria / class Anthozoa
subclass Alcyonaria: gorgonians, soft corals / subclass Zoantharia: zoanthids, anemones
• phylum Urochordata: encrusting, colonial tunicates
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Korallenriff-entstehung11 (see also Velimirov script2):
Das riff ist ein dynamisches system, welches ständigen veränderungen unterworfen ist (substrat-aufbau muss
dem substrat-abbau überlegen sein, sonst kommt es längerfristig zu einem “give-up reef” - ist speziell im zuge
der globalen klimaerwärmung relevant wenn “catch-up“ und “keep-up reefs” durch erhöhte bioerodive aktivität
und ungünstige abiotische bedingungen zu ersteren verkommen); dazu müssen verschiedene prozesse
zusammenspielen, die nachfolgend erläutert werden. Damit sich eine korallenkolonie entwickeln kann, muss
zunächst ein primärpolyp gebildet werden. Diese siedeln sich auf festem substrat an oder aber auf
abgestorbenen korallenkolonien; nur korallenpolypen, die sich in unzugänglichen ritzen befinden und vor
fressfeinden geschützt sind, können sich weiterentwickeln. Durch hoch- und seitwärtswachsen (knospung)
und ständige zusiedlung
vergrössern sich die einzelnen primärpolypen, bis sie sich vereinigen
und emporwachsen können. Freiliegende hohlräume werden rasch
zusedimentiert und durch die aktivität von kalkalgen verfestigt,
wodurch eine erfrolgreiche neu-besiedelung gewährleistet ist.
Voraussetzung für ein weiteres erfolgreiches wachstum ist seichtes,
klares wasser und genügend licht. Prinzipiell geht das wachstum
jedoch auf die anreicherung von abgeschiedenem kalk zurück;
durchschnittliche vertikale wachstumsraten liegen bei 1cm/jahr. Das
an der riffkante abgebröckelte kalkmaterial bildet eine schutthalde
auf dem sich, wie beschrieben, neue korallenstöcke entwickeln
Fig.5b riffentstehung
können.
Walker-Alberstadt Model of Reef Succession10)
Pioneer Stage
sediment accumulates in mounds
Colonization Stage
substrate is stabilized by cementer organisms
Climax Stage
structure influences wave patterns
organisms collect around mounds
crest is built up by framework
Lateral Zonation - communities
diversify and sediments differentiate
Coral animals - what is a coral?
The phylum Coelenterata (Cnidaria) consists of aquatic, largely marine, solitary and colonial, usually colorful
animals ranging in size from a few mm to 2m in length. Included in this phylum are the jelly fish, the sea
anemones and the corals. This phylum represents an important step in the evolution of more complex animals.
Im umgangsprachlichen gebrauch wird stattdessen gerne der begriff des korallentieres benutzt; unter diesem
oberflächlichen allgemein-begriff verbergen sich neben den scleractinidae (welche aragonit-CaCO3
prezipitieren) mehrere verschiedene sedentäre tiergruppen;
• falsche korallen sind den steinkorallen äusserlich sehr ähnlich, bilden aber kein CaCO3-skelett aus;
• weichkorallen, lederkorallen (Alcyonaria), die blumentiere unter den korallen bilden kein festes skelett, es
besteht nur aus einzelnen kalzit- skleriten;
• hornkorallen, edelkorallen (Gorgonaria) die tiere besitzen ein festes endoskelett;
• dornkorallen, schwarze korallen (Anthipatharia), kleine dornen, die auf dem schwarzen, verhornten (jedoch
nicht verkalkten) ectodermalen skelett aufgelagert sind.
• Alcyonacea, (rote, blaue korallen) mit namentlich zwei vertretern Tubipora musica und Heliopora coerulea;
• Milleporina (feuerkorallen) meist koloniebildende polypengeneration im generationswechsel mit der
medusengeneration;
• koralline Rhodophyta (Corallinaceae, kalk-rotalgen) eine zu den algen gehörende pflanze die in der lage ist
loses substrat in folge ihres metbolismus zu verfestigen;
auszug aus der systematik der korallentiere12
Superphylum
Phylum
Class
Subclass
Order
Familie
----------------------------------------------Coelenterata-----------------------------------------------------------------------------------------------Cnidaria------------------------------------------------Hydrozoa
Scyphozoa
---------------Anthozoa--------------Cubozoa
Hexakorallia
Octocorallia
↓
↓
↓
↓
Coenothecalia
Alcyonaria
Gorgonaria
Pennatularia
Hyroidea
Actiniaria
Stauromedusae
Coenothecalia
Trachylina
Telestacea
Madreporaria*
Coronatae
Siphonophora Semaeostomeae
Pennatulacea
Corallimorpharia
Milleporina
Alcyonacea
Anthipatharia
Rhizostomae
Stylasterina
Gorgonacea
Ceriantharia
Zoantharia
Rugosa (extinct)
Hydroidea
Scleractinidae
Cubomedusae
Rhizostanae
Helioporidae
Hydnocorallina
Tubiporidae
(s. references13)
Semaeostanae
Milleporidae
Coronatae
Legende:
1-fach unterstrichen: gruppe
enthält arten mit
rudimentärem skelett;
2-fach unterstrichen: gruppe
enthält arten die riffbildend
tätig sind;
*) ahermatypische
Madreporaria sind
azooxanthellaten, daher nur
bedingt riffbildend;
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Development of coelenterata31: der bauplan der Coelenterata ist in der regel nur aus zwei schichten
zusammengesetzt - das ectodermale und endodermale häutchen; das mesoderm ist nicht entwickelt. Dadurch
ergibt sich bei vielen arten ein sehr eigenartiges verhältnis von körper- zu wassermasse, die bei den medusen
gar zu 99% wasseranteil aufweisst.
Protostomia ("first mouth") are so called because the mouth develops from the first opening into the gut
(blastopore). The body cavity or coelom forms from a split in the embryonic middle tissue (mesoderm). Nach
der gastrulation (a process by which cells of the blastoderm are translocated to new positions in the embryo,
producing the three primary germ layers), setzt sich die gastrula mit dem aboralen pol an das substrat fest.
Fig. 6 Cross-sections of a juvenile sea anemone (Megalactis sp.) with three cycles of mesenteries: at left
a section at the level of the actinopharynx, at right a section nearer the base. (1) Indicates primary
mesenteries, of which there are six pairs; (2) indicates secondary mesenteries, of which there are six
pairs; and (3) indicates tertiary mesenteries, of which there are 12 pairs. In this example, the primary
mesenteries are complete (they connect to the actinopharynx, as in the left-hand image), whereas the
secondary and tertiary mesenteries are incomplete (they do not connect to the actinopharynx). Polyps of
some species have fewer cycles of mesenteries and some have many more, and the number of cycles of
complete mesenteries varies; these are all characters of systematic importance.14
Acnidaria15: die rippenquallen (Ctenophora) tragen keine nesselzellen und
wurden daher einem eigenen stamm, den Acnidaria zugeteilt, um sie
von den nesseltieren abzusetzen.
Ctenophores (Greek for "comb-bearers") have eight "comb rows" of
fused cilia arranged along the sides of the animal, clearly visible
along the red lines in these pictures. These cilia beat synchronously
and propel ctenophores through the water. Some species move with a
Fig. 7 Ctenophora
flapping motion of their lobes or undulations of the body. Many
ctenophores have two long tentacles, but some lack tentacles
completely. Ctenophores, variously known as comb jellies, sea
gooseberries, sea walnuts, or Venus's girdles, are voracious predators.
Unlike cnidarians with which they share several superficial similarities, they lack stinging cells. In order
to capture prey, ctenophores possess sticky cells called colloblasts attached to each of their tentacles. In a
few species, special cilia in the mouth are used for biting gelatinous prey.
Cnidaria16: the name Cnidaria comes from the Greek word "cnidos", which
means stinging nettle. Casually touching many cnidarians will make
it clear how they got their name when their nematocysts eject barbed
threads tipped with poison. Many thousands of cnidarian species live
in the world's oceans, from the tropics to the poles, from the surface
to the bottom. Some even burrow. A smaller number of species are
found in rivers and freshwater lakes.
There are four major groups of cnidarians: Anthozoa, which includes
true corals, anemones, and sea pens; Cubozoa, the amazing box
jellies with complex eyes and potent toxins; Hydrozoa, the most
diverse group with siphonophores, hydroids, fire corals, and many
medusae; and Scyphozoa, the true jellyfish. Cnidarians are incredibly
diverse in form, as evidenced by colonial siphonophores, massive
medusae and corals, feathery hydroids, and box jellies with complex
eyes.
Fig. 8 Fungiid
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Nematocyst16: these organelles originating from embryonic cells,
contain a coiled thread-like filament that can be rapidly everted like a
harpoon when triggered (via a cnidocil) by contact with an object or a
chemical stimulus. In many cnidarians, these nematocysts contain
powerful venoms (in some species even lethal for humans) that can
be used for defense or to capture prey. In order to efficiently capture
and paralyze the prey, nematocysts are found in batteries all over the
ectoderm.
Trichocysts17 are microscopic dart-like structures used for defense
by ciliates and some cnidarians.
Spirocyst: ist eine sonderform der trichocyten in der um das steife
zentralrohr ein klebriger faden gewunden ist.
Fig. 9 Nematocyst
Fig. 8 Trichocyst
18
Alternation of generation among cnidarians : bei der fortpflanzung
durchlaufen die nesseltiere einen sogenannten generationswechsel
(two-stage lifecycle). Larve, polyp und die glockenartige meduse, die
uns als "qualle" geläufig ist. Im unterschied zur metamorfose bei
insekten kann sich das individuum jedoch ungeschlechtlich
vermehren, noch bevor es das endstadium erreicht: es teilt einfach
mini-sprösslinge ab (ephrya), die wie knospen wachsen oder quer
abgeschnürt werden (strobilation). Allerdings durchlaufen nicht alle
nesseltiere die gleichen stadien, und manche kommen auch ohne
generationswechsel aus.
Class Scyphozoa32 (Gk. skyphos, cup; zoon, animal) inkludiert die gruppe
der echten quallen bzw. scheibenquallen; sie entstehen aus dem
polypen durch eine besondere art der knospung, der strobilation, am
Fig. 10 Lifecycle of Cnidaria
oberen ende eine reihe junger medusen (dominierende generation),
die bei ihnen Ephyra-larven genannt werden. Diese entwickeln sich
weiter zu geschlechtsreifen quallen; Scypho-medusen besitzen als
gravitationsdetektor statocysten und auch rudimentär ausgebildete
augen, jedoch kein velum. Vom polypen bleibt ein rest-körper haften,
der sich regeneriert und erneut strobilieren kann - er ist potentiell
unsterblich. Rund 200 arten sind weltweit bekannt. Zu ihnen gehören
die fahnenquallen wie die blaue haarqualle (Cyanea lamarkki) und
die gelbe (Cyanea capillata). Die meduse dieses als " feuerqualle"
bekannten tieres erreicht in der Arktis einen durch-messer von mehr
als 2m. Die ohrenqualle (Aurelia aurita) verträgt sowohl grosse
schwankungen der temperatur wie auch des salzgehalts im wasser
und ist daher in allen weltmeeren verbreitet. Sie ist leicht kenntlich
durch vier violette, ringförmige geschlechts-organe, die "ohren". Die
21
leucht-qualle (Pelagia noctiluca) hat die polypenform als anpassung Fig. 11 luminent Scyphozoa
an das hochseeleben völlig unterdrückt.
Auffällig sind auch die kompakt gebauten wurzelmund-quallen (Rhizostomea). Deren medusen kommen
auf einen durchmesser von bis zu 90cm.
• Order Stauromedusae33 (Gk. stauros, stake; medusa, one of the
Gorgons of Gk mythology having snakes for hair) include stalked
jellies (stiel- oder becherquallen): not all scyphozoa live the
mobile free-swimming existence. An attractive group known as
stauromedusae have forsaken the medusa stage and live their
entire lives associated with the benthos. Their planula larvae are
crawlers rather than swimmers. After selecting an appropriate
spot, the planula attaches and eventually develops into a polyplike form. Rather than strobilating like other scyphozoan polyps,
it develops directly into the stalked adult, thus retain their
sedentary lifestyle. Like coronate medusae, these scyphozoans Fig. 12 Lucernaria quadricornis;
retain vertical internal septa as adults.
charakteristisch sind die vier
Substrates such as seaweed and rock serve as sites for attachment.
armpaare.
Small crustaceans are the favoured prey, captured by 8 clusters of
knobby tentacles.
The wider portion of the body attached to the stem is known as the calyx. Many Stauromedusae have
cryptic colors and patterns and are difficult to find in their natural habitats. The photographs show the
typical stauromedusan body form.
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• Order Coronatae (L. coronatus, crown) die kronenquallen: the
coronate scyphomedusae include some of the most stunning of all
the jellies. Within Monterey Bay this group is nearly entirely
found only in deep midwater habitats. Among the coronates,
Periphylla periphylla is the only species known to be holoplanktonic without any kind of sessile polyp stage. It also lacks
the Ephyra stage and does not produce planula larvae like other
scyphozoans. Periphylla has a groove in the exumbrella (coronal
groove) that probably provides some flexibility to the relatively
Fig. 13 Periphylla periphylla
stiff bell. The bell may reach up to 20cm in height, has 16 lappets
around the margin, and is topped off by a conical apical tip.
The tentacles are stiff and 12 in number, and often held In an upward position. They form groups of
three that alternate with the 4 rhopalia. Through the transparent bell is seen a strikingly beautiful deep
reddish-brown stomach area. Presumably the brilliant pigmentation in this and other deep-water
jellies masks the light produced by ingested bioluminescent prey. Periphylla is a vertical migrator,
rising to shallower depths at night to feed on copepods and other crustaceans. It is found throughout
the worlds oceans, typically below 900 meters in Monterey Bay and as deep as 7000 meters in other
areas, but potentially at the surface in higher latitudes. Periphylla may reach much larger sizes in
Antarctic waters compared to temperate latitude populations. This species may be the most abundant,
widely distributed deep-water scyphozoan, and is commonly collected in midwater trawls by
scientists.
• Order Semaeostomae34 (Gk. semeia, standard; stoma, mouth)
includes moonjelly (ohrenqualle): moon jellies differ from other
large scyphomedusae in that they lack the long, potent stinging
tentacles that people generally associate with jellyfish. Instead,
the moon jelly may capture food on the surface of the bell using
mucus to ensnare zooplankton prey. Cilia transport the food to the
bell margin and tentacles, where it is passed to the frilly, conical
manubrium. With its high surface area, the manubrium also
probably functions directly in the capture of prey. The 4
Fig. 14 Aurelia aurata
horseshoe-shaped stomach pouches are readily visible at the top
center of the bell, as are the purplish gonads immediately beneath.
When a moon jelly has had a hefty meal, it's easy to see food packed in the stomach
pouches.Hundreds of fine, relatively short tentacles line the bell margin. The sting of this jelly is mild
and most people have only a minimal reaction to it, if at all. The bell is a striking translucent white,
diameter up to 40 cm, and may be tinged with pink or lavender. It is marked by 8 lobes, each with a
notch so that there appears to be 16 lobes, and 8 rhopalia. Sexes are readily distinguished since
females hold the fertilized eggs, which appear as whitish-gray clumps on the manubrium. Males may
sometimes be seen with long sperm filaments trailing from the oral arms.
• Order Rhizostomae35 (Gk. rhiza, cube; zoon, animal) the “upside-down” jelly (wurzelmund-quallen): a yellow brown jellyfish
with a circular body. Oral arms are a dark brown color.
Cassiopeia sp. live in warm, shallow waters. Many are found in
mangrove bays. Cassiopeia sp. lays upside down in order to
expose its symbiotic algae to the sun (make their own food from
light energy via photosynthesis). They shoot out nematocysts and
mucous (stinging stuff) to catch its prey; thus are mildly toxic and
Fig. 15 Cassiopeia sp.
contact with them causes a rash.
36
Class Cubozoa (Gk. kybos, cube; zoon, animal) the distinct box jellies
(würfel- oder feuerquallen): bei den würfelquallen (cubomeduse) reift
die planula zu einem winzigen cubopolypen heran. The bell of these
primarily tropical jellies is indeed somewhat cuboidal with 4
flattened sides. Box jellies tend to be transparent and can be quite
difficult to see in the water, even with large individuals. The bell
margin lacks any scallops and has a velum-like rim similar to that in
hydromedusae. Another characteristic, the possession of gastric
filaments, (similar to scyphozoans). A tentacle, or group of tentacles Fig. 16 Carybdea marsupialis
originate from each of the 4 corners. One of the more remarkable
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aspects of box jellies is their possession of a complex eye within each of the 4 rhopalia that enables them
to track moving objects and quickly respond to changes in light intensity. Cubozoa are elaborate
swimmers. Although the polyp stage is subordinate, they can reproduce asexually by budding to form
new polyps. They do not strobilate, however, and instead each develops directly into a small medusa
(polyp metamorphoses completely to axial-symmetry). Among the box jellies is the notorious sea wasp
of Australia (Chironex fleckeri37 and Chiropsaimus quadrigatus), which can have a fatal sting.
Class Hydroza (Gk. hydra, water serpent; zoon, animal): sie gelten als die
am höchsten entwickelte form unter den nesseltieren; rund 3000
bekannten arten gehören dieser klasse an, von denen 700 medusen
bilden. Aus den polypen (dominierende generation) wachsen durch
knospung ganze kolonien oder "stöcke". Die freischwimmenden
werden meist nur wenige zentimeter gross. Im gegensatz zu den
Scyphozoa besitzen Hydrozoa ein velum. Zu ihnen zählt der
süsswasser-polyp Hydra. In die klasse der hydrozoen werden auch
die staatsquallen (siphonophora) eingeordnet, die aus vielen
einzelpolypen oder -medusen bestehen. Die etwa 150 arten können
Fig. 17 Hydrozoan body plan
von wenigen mm bis zu mehreren metern lang sein.
• Order Trachylina19 (Gk. trachys,
mrough; L. linum, flax); planktonic
hydreomedusae with no polypoid
stage; this order contains perhaps
the most primitive members of the
class, Aglaura. These animals
Fig. 18a Voragonema
usually swim with their buccal
pedunculata (nat. size
cavity showing upwards.
approx. 2cm in diameter)
• Order Siphonophora20 (Gk. siphon,
tube; pherein, to bear); includes the
Portugese Man of War Jellyfish (Physalia physalis30); its tentacles
can exceed 16m in length, but do not pose a lethal threat to
humans. The “Portuguese Man of War” is a floating hydrozoan
colony. Locomotion is generally passive, driven by wind and
current. It is actually a colony consisting of four polyps: a
pneumatophore, or float; dactylozooids, or tentacles;
Fig. 18b Physalia physalis
gasterozooids, or siphons; and, gonozooids. Nematocysts
(stinging cells) are located in the tentacles. An important aspect of
the Man of War's behaviour is the symbiotic relationship between
the Man of War and the Nomeus (a minnowlike fish), a clownfish (commonly called the Man of War
fish), and the yellow-jack. These fishes live within the tentacles of a Physalia and are rarely seen
elsewhere. The fish, particularly the clownfish, produce slimy mucus that causes the Man of War not
to fire its nematocysts.
• order Hydroida24,29 (Gk.
hydra, water serpent;
eidos, form); kommen in 2
unterordnungen vor:
i) ANTHOMEDUSAE
(Athecata)
i) LEPTOMEDUSAE
(Thecata)
Dominierend ist das
Fig. 19b Body plan of hydroids
polypenstadium ?; bildet
Fig. 19a Regeneration of hydroids
sehr kleine weissliche
polypen aus die einer feder
sehr ähnlich sind, jedoch stark nesselnd wirken25. Im medusenstadium sind sie als kaum sichtbar nur
im mikroskop zu erkennen und führt so zum begriff des “nesselnden wassers“.
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Class Hydrocorallina (Gk. hydra, water serpent; korallion, coral); it includes Milleporina, Stylasterina,
Trachylina; the members of this class, which form colonies with massive skeletons of aragonite (calcium
carbonate). These two orders differ in details of skeletal construction and dactylozooid (prey-gathering
polyp) morphology. Sometimes grouped together in the family Hydrocorallidae26; both kind display a
reduced meduse stage with the dominant polyp stage:
• Order Milleporina27 (L. mille, thousand; poroa, pore) are known
as "fire corals" for their coral-like growth and their painful sting;
They are easily mistaken for true corals, whereas hydrocorallina
are colonial hydrozoans and secrete a massive calcareous skeleton
with a smooth surface; the polyps are connected by gastrovascular
canals. Hydrocorallina posses sensing dactylozooids that bear
clusters of nematocysts able to deliver a powerful sting and
feeding gastrozooids with tentacles. Hydrocorallina are common
components of coral reefs and even house zooxanthellae
(symbiotic algae residing in their tissue that photosynthesizes).
Fig. 20 Milleporidae
During their reproductive stage, they develop minute freeswimming medusae which are produced in sexual generations;
asexual "breaking" and splitting also generate "new" individuals.
Hierbei dominiert die polypengenration wohingegen die
medusen-generation wie bei den hydroida nesselndes wasser
generiert.
• order Stylasterina (lace or rose corals)28: ist eine kleine hydnokoralle die meist im schattigen bereichen des riffes anzutreffen
ist; sie ist besonders auffällig durch ihr stark intensiv violett
gefärbtes äusseres erscheinungsbild.
Class Anthozoa (Gk, anthos, flower; zoon, animal) are solitary polypoid
Fig. 21 Stylasteridae
cnidarians which lack a medusoid stage. The mouth opens into a
pharynx and gastrovascular cavity partitioned by mesenteries.
Subclass Octocorallia38 (Gk. okto, eight; korallion, coral) Although commonly called "soft corals," the
Octocorallia are not close relatives of the scleractinians, or "true corals“ living today. Unlike true corals,
which have hexaradial symmetry (multiple cycles of six), octocorals have 8-fold radial symmetry. In
addition; the small branches off of the main tentacle to give octocorallia a more or less feather-like
appearance. All octocorals are colonial polyps, and in some, such as the Pennatulacea, the polyps are
specialized for various functions. Except for the "blue coral" and "organ-pipe corals," few octocorals
produce substantial calcite carbonate skeletons; hence, the name "soft coral" for many of them. However,
most octocorals form spicules within their tissues, and some produce calcified holdfast structures or
long, rodlike internal supports; these parts can be preserved as fossils.
Octocorals are traditionally divided into six orders:
• order Telestacea39 (after the genus Telestos) include the branched
pipe corals and is a small group; colonies occur as simple or
branched stems arising from a creeping giving rise to large
upright polyps from which smaller, lateral polyps can arise,
giving the whole colony a tree-like appearance. The spicules are
united through calcareous secretions forming a skeleton (Hyman
1940). Although rarely imported due to their fragility, according
to Wilkens and Birkholz (1986) these corals do well under the
proper conditions and some species may be photosynthetic, while
others need to be fed planktonic foods.
• order Alcyonacea40 (after the genus Alcyonium) inkludiert die
lederkorallen und andere weichkorallen; hierbei sind die polypen
in die elastische mesogloea des zentralkörpers eingelagert, wobei Fig. 22 Stylatula sp. with a sand
letzterer durch spikel verfestigt ist. It contains all the most dweller (slug) Armina sp. on top
familiar genera of soft corals, such as Cladiella, Lobophytum,
Sarcophyton,
Sinularia,
Anthelia,
Xenia,
Capnella,
Dendronephthya, Lemnalia, Litophyton and Nephthea. All of
these genera, with the exception of Dendronephthya, have
zooxanthellae. Alcyonacea have fleshy or leathery colonies that
tend to be irregular in shape, with various lobes or finger-like
projections. Some resemble large toadstools (e.g., Sarcophyton
and Lobophytum), while others are more tree-like in shape (e.g.
Dendronephthya and Litophyton). Dendronephthya is especially
Fig. 23 Muricea sp.
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conspicous as it is almost transparent with soft hues while its spicules are vividly colored. Members
of these genera are limited to the Indo-Pacific region.
Anthelia and Xenia are two genera that are often confused with
each other, both genera rythmically open and close their polyps
with featherlike tentacles (not to catch planktonic organisms but
rather to improve ventilation). Anthelia tend to have longer, more
slender polyp stalks than Xenia, and they grow from an
encrusting, fleshy mat, whereas Xenia usually have a stalk with
polyps arising from the top of the stalk.
Xenidae (weichkorallen) bilden zuweilen regelrechte rasenbestände und wirken durch ihre rhythmischen bewegungen
fälschlicherweise als strömungsindikator (vielmehr wird die
ventilation gefördert). In diesen tiefen verschiebt sich dass
verhältnis zunehmends zugunsten der Alcynacea (weich- und
lederkorallen) - ist dieser trend
bereits in den lichtdurchfluteten
oberen
wasserschichten zu beobachten, so ist
das generell ein zeichen dass
es dem riff nicht gut geht!
Fig. 23b Dendronephthya sp.41
Fig. 23a Sarcophyton sp.41
with a feeding nudibranch
• Order Stolonifera41 (L. stolon, stalk, fer, to form); the polyps
arise singly from a creeping base. Calcareous spicules secreted in
mesenchyme; includes the so-called "organ-pipe corals" and tree
fern corals. Stolonifera are octocorals whose polyps arise from a
creeping base that may consist of separate, flat, root-like
structures called stolons, or an encrusting mat. The polyps in most
forms consist of two sections. The softer, thinner portion that
possesses the tentacles and mouth is called the anthocodia, and
this portion can retract into the lower, stiffer non-retractile portion
Fig. 24 Tubipora musica
called the anthostele. When retracted, star polyps (Cornularia
spp. and Clavularia spp.) will display this structure nicely.
In the Tubipora (red pipe organ coral), the spicules are so dense they fuse together to form a
calcareous skeleton; new polyps arise from stolons or from the transverse platforms.
• Order Gorgonacea39 (Gk. mythology, the Gorgons who had
snakes for hair): horny corals with calcareous spicules and small
or minute polyps; it includes sea fans, red coral, sea whips, and
sea feathers. Gorgonians have a strong, flexible interior axial
skeleton made of a horny material called gorgonin. This skeleton,
in the form of rods, provides for greater flexibility and support.
The skeleton is surrounded by a layer of tissue in which the
polyps are embedded. This tissue also contains numerous
conducting tubules and calcareous spicules. Although there are
some encrusting and single-stemmed species, the majority
resemble trees in their branched appearance. The precious deepwater red and pink corals of the Mediterranean, Japan and Hawaii
Fig. 25a Gorgonaceae40
are gorgonians too but they lack gorgonin, having instead fused
calcareous spicules that form the highly prized material from
which jewellery is made.
Photosynthetic Caribbean gorgonians have also gained a great
deal of attention from the medical community because they are
natural sources of some very interesting anti-inflammatory
chemical compounds, such as the prostaglandins (see Faulkner
1992). Entlang des überganges vom weichboden zum riffhang
findet man vielerorts peitschenkorallen (Elisella sp.) bzw.
Antipatharia (schwarze korallen). Die in diesen tiefen
Fig. 25b Elisella
vorherrschende schwache licht-einstrahlung und wasserbewegung
paraplexauroides
bedingt eine ausrichtung der sessilen fauna in längsrichtung (quer
zur strömung) um plankton aus dem wasser filtrieren zu können.
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• Order Pennatulacea42 (L. pennatulus, winged); the sea pens have
fleshy colonies with primary and secondary polyps; it includes sea
pens and sea pansies. As is the case for all octocorals, sea pens are
actually colonies of polyps. What distinguishes sea pens is polyp
dimorphism (entire organism is laterally symmetric). An apical
polyp grows very large and loses its tentacles, forming the central
axis. The base of this primary polyp forms a bulb which may be
expanded or contracted; the sea pen uses this bulb (not visible in
the picture to the right) to anchor itself in sandy substrates.
Branching off this primary polyp are various secondary polyps.
Fig. 26 Sarcoptilon sp.
Some, called autozooids, are typical feeding polyps. Others, the
larger and fewer siphonozooids, serve as intakes for water, which
circulates within the colony and helps keep it upright.
Also supporting the colony arecalcareous spicules and frequently a central axial rod of calcium
carbonate. In one group of sea pens, called the Subselliflorae, the secondary polyps are grouped into
“polyp leaves,” as in the Pacific species of Sarcoptilon shown here. The feather-like appearance of
these species gives the sea pens their common name; they look something like old-fashioned quill
pens. Most species, however, do not have polyp leaves, and look more like clubs, umbrellas, or
pinwheels.
• Order Helioporacea39 (Gk. helios, sun; poroa, pore) includes
only one genus, Heliopora, the so-called “blue coral” and is
limited to the central Indo-Pacific only. This species grows in
large brownish or greenish-gray mounds and has numerous
delicate white polyps over its surface. The colonies are heavily
calcified (aragonitic fibers fused into laminae) and thus appear
similar to Millepora. When dead or broken, one can see the blue
color of the skeleton caused by the infiltration of iron salts
(Hyman 1940). These photosynthetic corals are rarely available,
Fig. 27 Heliopora coerulea
but they do very well in aquariums.
Subclass Zooantharia39 (Gk. zoon, animal; anthos, flower); often termed Hexacorallia (belong to the
class Anthozoa); in contrast to Octocorallia exhibit a great deal of anatomical variation, which makes
them difficult to describe in general terms. Unlike the octocorals, hexacorals usually have tentacles and
internal polyp septa in multiples of six – although exceptions do occur – but never eight. The oral disc
has a prominent mouth that may be situated on a protuberance or have a protruding margin (Hyman
1940). The tentacles of the polyps do not have pinnules as in the octocorals. There are at present 6
recognized orders: Actiniaria, Antipatharia, Ceriantharia, Corallimorpharia, Scleractinia and Zoanthidae.
• Order Actiniaria42 (Gk. aktinos, ray) it contains all the organisms
we call sea anemones. They are quite diverse in their appearance,
ranging in size from a few cm to more than 40cm in diameter (in
the case of Stichodactyla gigantea).
The bottom of the anemone is formed into a basal disc (pedal disc
= fuss-scheibe) with which it attaches itself to the substrate or
even enables it to crawl along the surface. The other end contains
the mouth (oral disc) and is situated in the middle of a broad oral
disc surrounded by stinging tentacles of varying length and shape,
depending on the species. Many species of tropical anemone
contain zooxanthellae, but most temperate species do not.
Actinarian anemones can reproduce either sexually or asexually,
Fig. 28 Sea anemone
but they do not form true colonies with permanent tissue
connections between members, unlike the superficially similar
zoantharians.
• Order Antipatharia (Gk. antipathies, black coral) contain the
well-known precious black or thorny corals (dornkorallen,
schwarze korallen) out of which jewellery is made; usually found
at depths greater than 20m to depths of even 100m. These treeFig. 29 Antipathes sp.
like corals, that may well become 1-3m tall, have a thin chitinous
and black axial skeleton with small thorns made of a material –
similar to gorgonin. There is a thin veneer of living tissue from
which the simple “nakes” polyps arise. A.subpinnata is the
medirerranean representative, while A.dichotoma is found in the
Indo-Pacific.
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• Order Ceriantharia46 (Gk. kerion, honey comb; anthos, flower;
zylinderrosen): are non-photosynthetic, anemone-like anthozoans
that have a muscular, elongated, cylindrical body with a fleshy
foot that extends deep into the sand so that the oral end bearing
the tentacles extends outward. The tentacles tend to be extremely
fine and long, and some specimens of Cerianthus can sting quite
powerfully. These anemones are not photosynthetic, and as being
carnivors rely on passing prey. There are severel genera,
Cerianthus being mediterranean, while Pachycerianthus and
Arachnantus are found in the Indo-Pacific and the Caribbean
respectively.
• Order Corallimorpharia45 (Gk. korallion, coral; morph, form):
contain the popular mushroom anemones, which are not really
anemones – they are also known as “false corals” (falsche
korallen) and resemble stony corals, but lack skeletons. Polyps
can occur as solitary individuals, or in colonies. The tentacles are
usually reduced to knobs or small branched protuberances,
arranged around one or more mouths. These anthozoans do
contain zooxanthellae.
Various genera, such as Actinodiscus, Amplexidiscus, Discosoma,
Rhodactis and Ricordea, are included in this order.
• order Zoanthidae44 (Gk. zoon, animal; anthos, flower;
krustenanemonen): are a small group of solitary, but usually
colonial, anemone-like anthozoans in which all members are
connected by common tissue; zoanthids lack a skeleton and unlike
any other anthozoan internally, have a large number of paired and
unpaired septa (Hyman 1940). Zoanthid polyps can occur as
single individuals in large groups or they can be joined together
by a thin stolon, i.e. a thin or a very thick coenenchyme, from
which only the mouths and tentacles are visible (e.g. Palythoa
caribaeorum).
• Order Scleractinia47 (Gk. skleros, hard) are often termed
Madreporinaria (steinkorallen): represent the stony or hard corals.
Stony corals are basically anemones that are surrounded by a
calcareous skeleton. The polyps can be solitary or they can exist
in large colonies joined by a common tissue called coenenchyme.
Due to the colonial nature of many stony corals, they can build
massive structures that result in the development of entire coral
reefs. The majority of stony corals harbor zooxanthellae (thus
often termed zooxanthellates) and derive much of their nutritional
requirements from the metabolic products produced by the
zooxanthellae, while azooxanthellates do not house these
symbiotic dinoflagellates.
Fig. 30 Cerianthus lloydii
Fig. 31 Corynactis sp.
Fig. 33 Palythoa sp.
Fig. 32 Scleractinia
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PART II - Scleractinian coral reproduction and growth47:
Knowledge of coral reproduction has expanded greatly over the past 10 years into one of most intensely studied
aspects of coral biology. Review by Richmond and Hunter 1990 provides overview of status of knowledge.
Reproductive data are now available for about 210 of approx. 600 spp. of reef corals. What is most impressive
is the variety and versatility of coral reproduction both sexual and asexual.
Sexual reproduction: corals exhibit sexual and asexual reproduction. Unlike asexual reproduction, which
produces exact copies of the parent (clones), sexual reproduction offers two opportunities for new genetic
combinations to occur,
a) crossing over during meiosis, and
b) b) the genetic contribution of two different parents when an egg is fertilized by a sperm.
The individual coral polyp can be male, female, both or may not be reproductively active at all. If a polyp is
just of one sex then it is termed gonochoric. A polyp that is both male and female is known as a
hermaphrodite. In hermaphroditic corals; in order to prevent self-fertilization, male and female gametes
never mature at the same time. Die sexuelle vermehrung bei den korallen ist eine komplizierte
angelegenheit; bis dato wurden keine getrennt-geschlechtlichen polypen in einem korallenstock gefunden ?;
die sexuelle vermehrung kann auf zwei unterschiedliche vorgänge erfolgen:
Broadcasters: sexual fertilization of released positively buoyant gametes at very specific times so as to
ensure fertilization; fertilization is external at the water surface;
Many coral species mass spawn. Within a 24 hour period, all the corals from one species and often
within a genus release their eggs and sperm at the same time. This occurs in related species of
Montastraea, and in other genera such as Montipora, Platygra, Favia, and Favites (Wallace, 1994). In
some Montastraea and Acropora species, the eggs and sperm are released in a sack. They float to the
surface where they separate and fertilization takes place. Intraspecies fertilization is common but mass
spawning raises the possibility of hybridization by congeneric species (Wallace, 1994). The zygote
develops into larvae called planula which attaches itself to a suitable substrate and grows into a new
colony.
Brooders: asexually brooded planula larvae may be developed by a kind of budding (internal fertilization,
brooding of zygote, and release of planula, vivipary); some species of coral even brood their larvae. The
sperm fertilizes the egg before both are released from the coral. The larvae float to the top, settle, and
become another colony. Species of Acropora release brooded larvae.
Corals start their life as a free-swimming young (after spawning, the planula larvae is only the size of the
head of a pin) that are carried by ocean currents. The larvae will drift with the current until it finds a hard
bottom to attach itself. Once the larvae attaches to the bottom it quickly changes into a polyp (will never
move again). It reproduces by budding (in which an identical polyp sprouts out of the polyp’s side) and by
sexual reproduction (in which polyps release eggs and sperm, which mix in the water).
Fig. 34 Life cycle of corals58
Fig. 33 The generalised life cycle of a broadcast hard
coral59
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Reproductive variations among scleractinian corals:
A. Involves spawning fertilization and production of planula larvae.
B. Spawning: seasonal, monthly or annual.
C. Annual multi-species spawning occurs synchronously in >140 spp in GBR.
• Occurs 5 days after full moon in late spring (neap tides warm waters).
• Degree of synchronized spawning may be related to annual temperature range which is greater in
GBR than other reef regions; temperature change may provide seasonal cue.
• Lunar phase may fine tune the particular night for mass spawning.
D. Fertilization can occur externally through free release of gametes (broadcast spawning) or within
maternal polyp followed by brooding of larvae.
E. In hermatypic corals, spawners outnumber brooders.
• typical of corals in buttress and fore reef zones massive colonial forms with indeterminate growth
(e.g. Acropora, Montastrea spp. in Caribbean);
• broadcasters have high larval mortality but successful recruits can invade new environments with
lower competition;
• surviving colonies can live 100s of years;
• low recruitment rates are acceptable.
F. Most ahermatypes are brooders as are hermatypes living in disturbed, nearshore reef zones (e.g. Favia
fragum broods embryos for 3 weeks);
• zones with high adult mortality require high rates of recruitment; brooding produces mature planulae
ready to settle;
• brooding also found in Agaricia spp. A.humilis in shallow reefs and A.agaricites in deeper zones
which have high competition for spaces, as well as high rates of bioerosion.
G. Hermaphroditism is common in 68% of studied spp.
• egg and sperm production can occur on same mesentery or on differentiated mesenteries in same
polyp, in different polyps of same colony, or at different times in same colony (i.e. sequential as well
as simultaneous hermaphroditism).
H. Planula larvae are produced by both sexual and asexual modes of reproduction.
• Planula larve are cilliated and up to 1.6mm long.
• Some contain zooxanthellae when released from parental polyp.
• Some can live in plankton for up to 100 days.
• Helix experiment (Sammarco & Andrews) showed limited degree of dispersal from an isolated reef
in GBR and control by regional circulation patterns.
Coral spawning56: rhythmicity in moon phase luminance (29.5 day periodicity) appears to be the most
important environmental monthly spawning synchronizer. The main annual spawning season inducer appears to
be temperature variances. As the annual variation increases, the spawning season will shorten for monthly
brooding species whose minimum gonad development temperatures are not attained. Monthly brooders will
start to release planula based on the lunar periodicity of the ecosystem. The photoperiod of periodicity
combined with annual temperature variances are thus the key elements for the development of mass spawning
event.
Triggers in coral spawning57: • water temperature
• lunar cycle
• hours after dawn
Steps in sexual reproduction:
Fig. 35a Coral releasing
eggs (top) and sperm
(below) 52
Fig. 35b Fertilization at the
surface (top); eggs and zygotes
of Acropora palmata (below)52
Fig. 35c early (top) and
later (bottom)
development of planula
larvae belonging to
Acropora sp.52
Fig. 35d a week old
Montastraea faveolata (top, ca.
0.5mm); young polyp settled on
a suitable substrate (below)52
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Corals can reproduce also vegetatively. The term asexually can be referred to as vegetative and the term
sexually as generative. Through asexual reproduction, a coral can make a clone of itself. The two methods of
asexual reproduction are able to eventually give rise to an entire colony. Individual corals can reproduce
through by transversal division. In this way, coral colonies are able to live for a few hundred years. Asexual
reproduction is thus the main cause of coral growth.
Asexual modes of reproduction to ensure colony growth - budding of polyps from a parent colony.
A. “Polyp bailout”: polyp abandons corallite, and re-establishes on a new substratum.
B. Fragmentation: colonies broken up during storms can initiate many new colonies.
• Common in branching forms.
• Important for spp. at limits of distribution where conditions might not favor sexual reproduction or in
stressful habitats without optimal regions.
C. Colony growth is by asexual multiplication.
• Budding of polyps from a parent colony.
• Peripheral increase by fission.
Colonies can grow in the following manner:
1) by producing stolons: stolons horizontally grow cell layers. They look like a system of roots that fix the
whole colony to substrate. New polyps grow on stolons;
2) by monopodial growth: this term means that the trunk of the colony is made by the oldest polyp. The trunk
grows during growth of new polyps. The oldest polyp is always on top of the colony;
3) by sympodial growth: this colony does not produce a trunk. New polyps offshoot along the edges of adult
polyps. The youngest polyps are always on top of colony;
4) by dychotomic growth: dychotomic growth means that the corals divide symmetrically. Since all polyps
grow simultaneously, neighbor polyps are the same age.
Budding (knospung) 50: the coral colony expands in size by budding. In the
process of budding, a young coral individual grows out from the adult
(parent) polyp. This is the way a colony grows. Within the reach of
the oral disc or beyond the wreath of tentacles on an adult polyp, a
daughter polyp forms. The progeny polyp has two cell layers:
ectodermis and gastrodermis. As the progeny polyp grows, it
Fig. 36 intra- (left) vs. extraproduces a coelenteron, tentacles and a mouth. Sometimes, the young
(right) tentacular budding
polyp can originate beyond the wreath of tentacles.
The distance between the polyps increases which causes development of coenosarc (the common body of
the colony). New polyps grow on the coenosarc by producing new coenosteum, the colony’s
exoskeleton. Budding may be intra-tentacular, in which the new bud forms from the oral discs of the
old polyp, as in Diploria sp., or extra-tentacular in which the new polyp forms from the base of the old
polyp, as in Montastraea cavernosa.
• intra-tentakuläre knospung: zwei gleich grosse tochterpolypen gehen aus einem elterlichen polyp
hervor, verbleibt aber noch während der teilung innerhalb des elterlichen tentakelkranzes; bildet in
meandrierenden formen ganze polypenreihen;
• extra-tentakuläre knospung: die folge-generation geht aus dem elterlichen polypen hervor wobei
sich zwei gleichgrosse, neue einzelpolypen entstehen (niemals reihen).
• longitudinal division: in longitudinal division, the coral polyp begins to broaden; it then divides into
a coelenteron and mesenteries; next, the mouth divides and tentacles encircle the new mouth. The
difference from the above is that during budding, the parent polyp produces a smaller polyp, whereas
after division, the two polyps are identical. There is no distinction of parent and daughter polyps in a
division. Individual polyps divide according to the radial arrangement of septa. Every new part has to
complete its missing parts of the body and exoskeleton.
• transversal division: individual corals are able to reproduce by transversal division. Polyps and the
exoskeleton divides transversally into two parts. One of them has the basal disc. The second has the
oral disc. The two new polyps must complete missing parts of the body and exoskeleton in order to
function.
Fission: some corals (esp. mushroom corals among the family Fungiidae) are able to split into two or more
colonies during the early stages of their development (also called strobilization);
Fragmentation: last method for coral colonies to propagate is through a process of fragmentation. A piece of
colony can actually be broken off to grow a clone.
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Reproduction in Fungiidae60: laut Veron (1986) sind wahrscheinlich alle Fungiidae getrennt geschlechtlich,
wobei die weiblichen korallen entweder eizellen oder sexuell erbrütete planulae ins wasser entlassen. Viele
pilzkorallen (Wood 1983 Heliofungia, alle Fungia-, Cycloseris- und Diaseris-arten) besitzen eine
eigenartige geschlechtliche fortpflanzung, aus der sogenannte anthocauli hervorgehen. Als anthocaulus
wird der sessile, gestielte jungpolyp bezeichnet, der sich aus der festgesetzten planula-larve entwickelt.
Anthocauli führen meist ein ziemlich verborgenes leben in strömungsgeschützten, schwach beleuchteten
nischen von hardsubstraten. Während des wachstums verlängert sich der basale stiel und verbreitert sich die
mundscheibe (= anthocyathus) hutartig - daher auch der name “pilzkorallen”. Mit erreichen eines
mundscheiben-durchmessers von maximal etwa 4cm bricht der anthocyathus vom stiel ab und wächst als
frei auf dem boden lebende koralle weiter. Der biologische vorteil dieser zunächst sessilen lebensweise
dürfte mit dem veränderlichen, sedimentations- und zeitweilig sehr strömungsreichen lebensraum der
pilzkorallen zusammenhängen, in dem aus planula-larven entstehende jungpolypen vermutlich geringere
überlebens-chancen hätten. Anthocauli können aber auch (bei vermutlich allen Fungiidae) ungeschlechtlich
entstehen, in form von kleinen tochterpolypen an der ober- oder unterseite der frei lebenden pilzkorallen.
Werden pilzkorallen von grobsedimenten so sehr zugeschüttet, dass sie sich davon nicht mehr befreien
können, oder werden geschwächte exemplare von kalk-rotalgen oder anderen sessilen organismen
überwachsen, wird dadurch noch lebendes polypengewebe zur bildung von anthocauli angeregt. Doch nicht
nur als quasi letzte überlebens-strategie, sondern auch von gering beschädigten oder gesunden pilzkorallen
werden hin und wieder solche anthocauli gebildet. Laut Veron soll der anthocaulus-stiel nach ablösung der
mundscheibe absterben, doch haben aquarien-beobachtungen gezeigt, dass zumindest bei Fungia spp.
sowohl ungeschlechtlich als auch geschlechtlich entstandene anthocauli zu einer mehrfachen mundscheibenbildung in folge befähigt sind (Stüber 1994; Fossa & Nilsen 1995).
Coral growth rates: Most corals are a colony of many individual polyps, in which each polyp contains
dinoflagellates (zooxanthellae) capable of photosynthesis. Without zooxanthellae, the polyps cannot grow fast
enough to build reefs (see pages 21, 22). Reef-building corals precipit up to 6 tons CaCO3/(km2⋅day). By night,
a polyp captures plankton with its tentacles. By day, the zooxanthellae photosynthesize. The polyp benefits
from the photosynthate (product of photosynthesis), and the alga benefits from the nitrogenous wastes of the
polyp. There is an intense competition for space. Corals have a rigid pecking order. When more aggressive
species recognize less aggressive forms, they send out nasty mesentary filaments as well as sweeper tentacles
that wound living coral encroaching on their space. More than 65 species have been found in Caribbean reefs:
there are both shallow, fast-growing forms and deep, massive, slow-growing forms (living at a maximum depth
of about 30m). The Great Barrier Reef (GBR) of the Indo-Pacific has 350 named coral species.
A. Methods of study
1. Linear or radial growth using stain markers (alizarin), dense banding, etc. ;
2. Colony weight;
3. Radioisotopes;
B. Variations of growth form: highly variable but open, branching colonies grow faster in linear dimension
than massive colonies with dense skeletons. Branching forms have greater S/V ratio.
1. Branching forms: 100-200mm/yr (staghorn Acropora)
2. Massive colonies: 6-12mm/yr, but colonies (clones) can live for centuries.
3. Using colony weight: branching forms grow faster in proportion to surface area. However, there is no
evidence of senility; calcification rate/cm2 is similar for small and large colonies.
C. Diurnal, seasonal and long term variations (see Velimirov script2).
1. Diurnal: growth is 14x faster by day in zooxanthellate corals, as determined by Goreau’s 45Ca tracers.
2. Seasonal: grow rates vary reflecting seasonal changes; e.g. Porites furcata in Caribbean Panama.
a) Colonies stained using alizarin red to mark wet and dry seasons.
b) Over 2 successive years. Wet season rates exceeds dry season rates. About 3 mm/month in wet,
versus <2mm/month in dry. Why the difference?
c) Wet season May to December;
• heavy rainfall, cloud cover;
• calmer seas . esp. when ITCZ is south of Isthmus;
d) Dry season December to May;
• more sunshine, less rainfall;
• strong onshore traces from E-NE;
• seas are rough, waters turbid;
e) During dry season, Porites polyps are retracted more of the time to protect from abrasion. Thus
less exposure to light; growth is reduced. During wet, polyps open more of time in calmer seas.
f) Other studies have found faster growth correlates with times of greater sunshine, but here other
physical factors override effect of solar radiation.
3. Long term: using density bands, long records of growth can be obtained (see Shinn paper). Also
recent study of Red Sea Porites, dating back to as far as 1880.
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Morphology of scleractinian corals: Nach erfolgreicher ansiedlung der planula
larve auf passendem hardsubstrat, erfolgt die ausbildung einer basalplatte aus
aragonit48 (CaCO3); aufgrund der septenstruktur wird der hohlraum
(disseptimente und theca) aufgebaut. Zur erinnerung, die septen sind
bestandteile des ektoderms; sie liegen zwischen zwei häutchen (= innenhaut der
mesenterien) und sind die Ca-abscheidenden organe des korallengewebes.
Sobald die basalplatte angelegt ist, beginnt die jungkoralle mit dem aufbau der
seitenwände wodurch der kelch (calix, calice) getrennt wird. Durch einziehen
von zwischenwänden (disseptiments) in regelmässigen abständen wird die
abgeschiedene struktur zusätzlich stabilisiert; erst jetzt ist die aufbaufase
abgeschlossen und die koralle kann mit dem nächsten wachstumszyklus
(abscheidung der seiten- und zwischenwand) fortfahren, wodurch die koralle an
höhe zulegt. Das organische material unterhalb der aufgebauten disseptimente
stirbt dabei ab; folglich ist nur das hauchdünne gewebe (coenosarc) als das
biologisch aktive gewebe für den aufbau der skelettstruktur verantwortlich.
Koloniebildende arten sind so aufgebaut dass benachbarte polypen durch ein
locker strukturierte fülmasse (coenosteum = exothecale disseptimente) getrennt Fig. 37 struktur der korallen
sind; je nach art kann es mehr oder weniger mächtig (dünnwandig sein).
Das gesamte erscheinungsbild des abgeschiedenen skelettes ist letztendlich artbestimmend, wodurch sich die
arten relativ gut (in manchen fällen nicht so leicht) unterscheiden lassen.
Some structural elements of such corals49:
• corallite: skeleton of a solitary
individual or an individual within a
colony;
• calice: a cup-shaped depression on
the corallite surface;
• coenosteum (-a) [or peritheca (-ae)]:
skeleton between corallites within a
colony;
• septum
(-a):
radially-arranged
vertical partition(s) within a corallite;
they can be either exsert, insert of
even in regard to the corallite wall;
an
exsert
• paliform
lobe:
protuberance of a septum at the
center of the corallite;
• wall [or theca (-ae)]: vertical
structure enclosing a corallite;
• theca: the sheath of “dura mater”
which encloses a corallite;
• costa (-ae): extension of a septum
beyond the wall;
• costa (-ae): a rib or riblike structure;
• columella (-ae): central axial structure within a corallite;
if present, it can be formed either as a
solid columella: a central rod;
spongy columella: formed by the inner ends of septa;
papillose columella: may small rods; or
lamellar columella: plate-like;
• dissepiment: horizontal partition (flat or curved) within
or outside of a corallite;
• synapticulum (-ae): a conical or cylindrical supporting
process, as those extending b/w septa in some corals;
• coensarc: the living axial part of a coral colony (=
peritheca);
• peritheca: the living tissue surrounding or between
corallites (= coenosarc);
• coenenchyme (=coenosarc) the mesogloea surrounding
and uniting the polyps in compound anthozoans;
• mesentery: a fold of the peritoneum that connects the
intestine with the posterior abdominal wall.
Fig. 38 coral anatomy (top) vs. coral structure
and features (bottom)59
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Corallite growth-form of colony-forming stony corals54: die koralliten-anordnung einer kolonie ist ein
wesentliches erkennungsmerkmal zur artunterscheidung;
Fig. 39a plocoid: short
Fig. 39b cerioid: corallites
stalked corallites separated juxtaposed, and are even
by coenosteum
while each corallite retains
its own wall; massive
corals that have corallites
sharing common walls
Fig. 39c meandroid:
corallites arranged in
multiple series (due to
intra-tentac. Budding);
massive corals with coral
mouths aligned in valleys
separated by ridge;
adjacent valleys share the
same ridge
Fig. 39d flabelloid:
corallites arranged in
single series;
corallites in long
meandering rows or
valleys that share a
common base, however
the walls (or ridges) of
adjacent valleys are not
connected
subplocoid: corallites
sometimes separated by
coenosteum
Fig. 39e flabellomeandroid: corallites in
long meandering rows
with common base; walls
may be partially fused.
This condition is also
referred to as flabellate
Fig. 39i thamnasterioid:
the septa of adjacent
corallites are confluent
and often twisted or
sinuous in form; plating
coral with no walls
surrounding corallites
Fig. 39f phaceloid:
corallites separated by
void space; corals that
have corallites with
distinct walls separated by
coenosteum
Fig. 39j hydnophoroid:
coral with cone-shaped
protuberances between
corallites
Fig. 39g solitary:
corallum formed by only
one individual
Fig. 39h dendroid: the
corallites branch from
each other in a dendritic
pattern; derives from
extra-tentacular budding
(extinct)
Fig. 39k fasciculate: the corallites are cylindrical but
not in contact. It may be dendroid (with irregular
branches) or phaceloid (with more or less subparallel
corallites with connecting processes).
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Colony growth-form of stony corals (scleractinia)55:
Acroporidea growth form:
arborescent- colonies typically composed of tree-like branches;
bottlebrush - colonies have small branchlets coming out from the sides
of the main branch;
caespitose - Colonies are "bushy", consisting of possibly fused branches
inclined at various angles;
corymbose - colonies are composed of horizontal (possibly fused)
branches, with short vertical branchlets;
digitate - Colonies are composed of short, non-dividing branches,
similar to fingers;
encrusting - colony adheres to the substrate;
flat plates or whorls - plates generally are horizontal, upward facing
side with polyps. Whorls tend to be "double-sided" with polyps and
are vertical;
table - colonies are flat and attached either with a central foot or on one
side to the substrate;
Fig. 40a morphology of a coral
colony53
general coral growth form:
massive: mounding, mound-shaped or encrusting colony; similar in all
dimensions;
branching: colony composed of elongate projections, arborescent, or tree-like to digitate or finger-like
platy: laminar, flattened or sheet-like, may be vertical or horizontal colony with calices on only one
(monofacial) or both side (bifacial);
foliaceous: leaf-like, thin, folded plates or spires extending upward.
Fig. 40b arborescent
Fig. 40c bottlebrush
Fig. 40e corymbose
Fig. 40d caespitose
Fig. 40f digitate
Fig. 40i table
Fig. 40g encrusting
Fig. 40h flat plates or
whorls
Fig. 40j massive
Fig. 40k foliaceous
Fig. 40l leafy
Fig. 40k solitary
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Physiology of scleractinian corals61: alle riffbildenden korallen leben in symbiose mit einzelligen algen
(zooxanthellen), die eminent wichtig für die kalkbildung sind. Diese endosymbiontischen algen können, wie
jede pflanze, ihre fotosynthese nur bei ausreichend licht durchführen.
Coral-Algae Symbiosis - my best friends are plants:
Symbiosis is the key to understanding ecology of coral reefs and the success of reef-building corals.
A. Symbiosis: a close association of two species.
1. Both species live closely together. In some cases one species may live inside another (endosymbiosis
- endosymbionts.)
2. No implication of benefit or harm to associates.
B. Mutualism: an association of two species in which each species derives benefit from the association.
May be an interdependent association; e.g. lichen = algae + fungi.
Reef-building (hermatypic) corals are characterized by presence within their gastrodermal tissues and oral
discs of endosymbiotic algae called zooxanthellae.
A. Zooxanthellae are minute, spherical unicellular algae belonging to the dinoflagellates.
B. Zooxanthellae are acquired during the planula larval stage and proliferate as coral grows.
C. If algae are isolated from host and cultured, they transform into typical biflagellate, motile dinos.
D. Algae can be expelled from host under stressful conditions such as seen in recent coral bleachings, and
can be reacquired.
E. Means by which corals are “infected” unclear but probably through ingestion, since algae reside in
gastrodermis of host.
F. Whether >1 species of algae acts as the symbiont to all corals (as well as other hosts) or a single species
is not clear, although there is evidence of different genetic strains in different hosts.
G. All reef-building corals are zooxanthellate, but not all zooxanthellate corals are reef builders. Nonzooxanthellate corals are not reef builders (ahermatypic).
H. Other marine invertebrates that harbor zooxanthellae: Tridacna (giant clam), nudibranchs (Tridachia),
Cassiopeia jellyfish, sponges, anemones.
Nature of the relationship between zooxanthellae and coral has been a major problem and subject of debate.
Alternative hypotheses include the ff.
A. Algae are a food source for host.
1. Although corals are known to be micro-carnivores, feeding on zooplankton, this food source may be
insufficient to sustain coral growth.
2. Under starvation, corals expel algae and die.
3. Through use of radioisotope 14C, experiments showed that tracer is fixed by zooxanthellae and later
dispersed throughout host tissues. In Zooanthus, products of photosynthesis are directly transferred to
host (such as glycerol, glucose, alanine).
4. Algae themselves are not digested, but 94-98% of organic carbon produced by algae is utilized by
coral host.
B. Corals are variably dependent on zooxanthellae.
1. Porter (1976) plotted caribbean coral species on axes of polyp diameter (DP) vs. surface area to
volume ratio (AS/V) of live tissue volume of skeleton plus tissue.
2. P is a good measure of zooplankton-catching ability while s?n provides a measure of light-gathering
ability. ?
3. Resulting hyperbolic distribution suggests a spectrum of dependence on algae, although even those
with low (sn?) input must have some help from algae.
4. Porter found that Montastrea cavernosa obtains only 10-20% of daily energy needs during 2 most
successful hours of nocturnal zooplankton feeding.
5. Occurrence of a Porites colony within osculum of a sponge suggests zooplankton feeding is not
essential for nutrition (Porter, 1974).
C. Zooxanthellae aid in skeletal excretion.
1. Zooxanthellae remove phosphorus as a waste product from coral. Because dissolved phosphate may
inhibit calcification, this may benefit growth of coral skeleton.
2. Also remove waste CO2 from coral.
D. Zooxanthellae enhance coral calcification.
1. Lab and field experiments of Goreaus using 45Ca showed calcification 2-3x greater in the light.
2. Corals kept in the dark cannot calcify as rapidly and eventually expel zooxanthellae.
3. Photosynthesis reaction: 6CO2 + 6H2O → C6H12O6 + 6O12
4. Hydrocarbonate reaction: CO2 + H2O → H2CO3 → H+ + HCO35. Calcification reaction: Ca++ + 2HCO3 = Ca(HCO3)2 ↔ CaCO3↓ + H2O + CO2↑
6. Removal of CO2 through photosynthesis will enhance calcium carbonate precipitation.
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F. Does O2 production by algae benefit coral? Probably not, since reef
waters are usually rich in O2.
G. Algae benefit in receiving CO2 and other wastes from coral, as well as
gaining a living place, almost a “culture medium.”
Additional modes of coral nutrition.
A. Particle feeding using mucous nets and strings.
B. Direct absorption of dissolved organic matter through ectodermis.
Für die mechanismen der kalzifikation und carnivore ernährungsweise siehe
Velimirov-script2.
Nearly 90% of the carbon fixed by zooxanthellae is released to the coral host
primarily as glycerol. Nitrogen and phosphorous derived from captured
Fig. 41a Nutritional balance
plankton are shared between symbiont and host. The contribution made to
the calcification process is of pivotal importance to this discussion. While this link is well known, the precise
pathways along which it occurs remain the subject of considerable discussion (Gladfelter, 1985).
Zooxanthellae are unicellular yellow-brown (dinoflagellate) algae which
live symbiotically in the gastrodermis of reef-building corals. It is the
nutrients supplied by the zooxanthellae that make it possible for the
corals to grow and reproduce quickly enough to create reefs. Zooxanthellae provide the corals with food in the form of photosynthetic
products. In turn, the coral provides protection and access to light for
the zooxanthellae. Because of the need for light, corals containing
zooxanthellae only live in ocean waters less than 100 meters deep.
They only can live in waters above 20°C and are intol-erant of low
salinity and high turbidity. It was once believed that all zooxanthellae
were the same species, Symbiodinium microadriaticum62. However,
zooxanthellae of various corals have been found to belong to at least
10 different algal taxa. Interestingly, zooxanthellae found in closely
related coral species are not necessarily closely related themselves,
and zooxanthellae found in distantly related coral species may, in
fact, be closely related (Rowan and Powers, 1991). This suggests that
coral and zooxanthellae evolution did not occur in permanently
associated lineages. Rather, symbiotic recombination probably
shaped the evolutionary process, allowing both symbionts to evolve
separately. Der lichtfaktor verhindert also riffbildung in grossen
tiefen und in planktonreichen meeren. Es sind keine zooxanthellate
riffe gefunden worden, die tiefer als 100m unter der meeresoberfläche sind. Die korallenfärbung ist durch die eingelagerten
zooxanthellaten verursacht (protisten aus der gruppe der
dinoflagellaten der gattungen Gymnodium = Symbiodinium), z.b.
S.microadriaticum. Im allgemeinen fall wird die alge mit der planula
Fig. 41b Gymnodium
larve weitergegeben, sodass die jungkoralle schon nach der
microadriaticum
metamorfose mit dem aufbau einer kolonie beginnen kann.
Im zuge einer korallenbleiche gehen viele zooxanthellen durch exocytose verloren; ist die zeitdauer der
externen stress-einwirkung zu gross werden dass selbst die noch wenigen verbliebenen endosymbionten
exocystieren, so kann die koralle selbst nach ende der stress-einwirkung keine neuen zooxanthellen
kultivieren und geht letztendlich kaputt. Korallenkolonien die in lagunen gedeihen sind auf einen
ausreichenden
wasser-austausch
angewiesen um ein exocystieren der
endosymbionten zu vermeiden; oft
verhindert die wasser-luft grenze ein
weiterwachsen nach oben, wodurch der
stock apikal abstirbt (UV-einwirkung und
längeres trockenfallen lösen exocytose
aus), kann allerdings durch laterales
wachstum
eine
mikroatoll-struktur
annehmen
(koloniezentrum
erfährt
vertiefung, ist bei Porites-kolonien häufig
zu beobachten).
Fig. 41c SEM of zooxanthellae.
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PART III - Reef zonation64:
There are four basic types of coral reefs; fringing, barrier, platform, and atoll (for details see Velimirovscript2):
• Fringing reefs are located very close to shore, and because of water run off they are typically high in
nutrients and the water has a high turbidity.
• Barrier reefs are further from the shore, with a "lagoon" between the reef and the shore.
• Platform reefs are formed in midocean locations, and at the edges of continental shelfs.
• And finally atolls are a circular reef with a central lagoon and possibly small islands formed on the reef.
It is theorised that each of these types of reefs corresponds to a differing age of the entire reef structure. The
youngest is the fringing reef, with the corals colonizing a shallow water area close to the land. If the sea levels
then rise or the land subsides, then the reef structure keeps up with this changing depth by growing upward.
Eventually a shallow area with no coral growth will form behind the main reef, called a lagoon, giving a barrier
reef. If the sea level or land subsides so much as to cause the land to disappear below the water surface, then an
atoll is formed.
The overall type of the reef whether it is a turbid, high nutrient reef where the stony corals are less common and
algae abounds or crystal clear, low nutrient reef where the stony corals can dominate, is dependent of several
factors. These include the proximity to land (therefore water run off which will be high in nutrients), proximity
to river mouths (for the same reason as land proximity), and location of deep sea currents (which typically bring
nutrient rich water. Each type of reef is also divided into various zones within each reef.
Fig. 42a Coral Reef distribution and diversity: coral reef development is restricted to the low-latitude
area between the two 18°C temperature lines shown on the map. Minimum water temperatures of 18°C
in surface waters of the Northern and Southern hemispheres occur in February and August, respectively.
In each ocean basin, the coral reef belt is wider and the diversity of coral genera is greater on the western
side of the ocean basins (after Stehli and Wells, 1971).
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What is coral reef zonation? Zonation is a very important concept when considering any ecosystem, with coral
reefs being no exception. A particular ecosystem will typically be divided into zones, each zone having a
particular set of physical parameters, such as light intensity, that set it aside from any other part of the
ecosystem. A zone is defined by its physical parameters and location within the ecosystem. Within a particular
zone, various organisms will have evolved such that they are adapted to thrive under those specific conditions
that are present within that zone. It can undoubtedly live somewhere else, in a similar zone or sometimes even
one vastly different, but there is always one in which it will be perfectly suited and as a result outcompete any
other organisms that occupies that niche in the food web.
What determines coral reef zonation? Zonation within a reef is typically determined by:
a) the light intensity received, which is dependent of the depth and turbidity of the water;
b) position relative to the open ocean or river mouths;
c) deep ocean currents; and
d) localized water currents.
Each of these parameters interact to give the final conditions that are characteristic of that zone. The most
dominant parameter is the light intensity, which is the major source of energy for the reef community. And
because this is directly related to the depth; depth can be used as a very good indicator of the predominant
conditions.
As a general rule with increasing water depth:
• light intensity drops;
• blue light increasingly becomes the more dominant wavelengths in the light spectrum, as the other
wavelengths are absorbed more rapidly by the water;
• wave surges become less intense, but currents can still remain strong;
• water temperature falls and becomes more constant (a reason why bleaching usually takes place within
the first 10-15m depth range).
Therefore the particular organisms that are present
on the reef alter with the depth, as each one has
evolved to fit best into one area. The organism can
also alter its behavior depending on the zone, with
the physical conditions having a large effect on its
behavior and even its appearance. This is
graphically shown by many of the stony corals. In
the shallow, high light intensity and extreme water
motion zones they will form fingered or massive
(domed) structures. As the depth increases, light
intensity rapidly drops off and wave surges are
reduced, but the currents can still remain strong. To
adapt to this lower availability of light, stony corals
then take on thin, flattened plates therefore
increasing the surface area that is exposed to light.
Storms are another factor that can also affect and
Fig. 42b Reef Zonation
alter the zonation of a reef.
The force of the waves and associated surges batter the reef structure, break some of the reef building corals
weakened by boring organisms, distribute erodied sediments, and erode the shores of coral cays.
Deep Forereef: the forereef slope is the least consistent of any of the reef
zones, in either its occurrence or character. At many sites, it is totally
absent and the forereef drops from shallow water to oceanic depths.
Where a forereef slope is present, the deep forereef usually occurs as
a well-defined ridge near the platform margin. Otherwise, it is simply
a down-dip extension of the forereef. When occurring separate from
the shallower reef zones, the location of the deep forereef is probably
controlled by both the break in slope and the existence of an
antecedent high left by a previous reef. The character of the reef
surface is often similar to the spur-and-groove topography described
within the forereef section, except that the scale of both the reef
promontories and the intervening channels is generally larger. The
Deep Fore Reef Slope (50 - 300m deep), represents the seaward limit
of the reef. Typically, this boundary is a steep underwater cliff (often
referred to as “the Wall”) where organisms cling to irregular rocky
ledges. As sunlight gradually disappears, the reef biota give way to a
community of sponges and deep-water, non-reef-building corals.
Fig. 43a Deep Forereef
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In this image, note the steep slope
(about 70o) of the reef rising.
Perhaps the most dramatic feature
of the deep forereef is the “reef
wall”. At depths ranging from 50
to 85m around the Caribbean, the
forereef slope rolls over to a
vertical or, in some places,
overhanging precipice. The role
of active accretion at this depth is
not well understood, owing to its
remoteness. Along the highenergy margin of the Great
Barrier Reef, coral cover is
Fig. 43b Coral gradient
apparently limited to a very thin
veneer over the antecedent Pleistocene reef front (Isdale, 1984). Along the front of the Belize barrier
reef, several episodes of reefwall accretion have probably occurred (James & Ginsburg,
1979).Compression of the coral; reef zonation is accompanied by some changes in the coral community,
with the less sediment-tolerant (Montastraea annularis, Agaricia agaricites and Acropora palmata)
being reduced in present of total cover.
Reef Slope: below 20m in depth on the reef front is the reef slope – the reef
has extended into deeper offshore waters. Because of the increased
depth, sunlight is not as intense. In response to lowered light levels,
corals adapt and grow as large plates. Some of the plates seen here
are species which form rounded heads in shallow water. At these
levels the blue part of the light spectrum dominates and the light
available is vastly lower than that at the surface. Corals expand
horizontally in shape in order to capture as much sunlight as possible.
Therefore any branching species that are found in shallower waters
are largely replaced by plate-like forms of the same species.
Gorgonian fans (Gorgonacea) are very prolific in this zone, along
with the feather stars (Crinoidea) that are associated with gorgonians.
The dominant genera present are:
Scleractinians: Echinopora, Porites, Turbinaria, and Acropora.
(indo-pacific only: A.hyacinthus, A.clathrata, A.cytherea)
Alcyonaceans: Dedronephthya.
Gorgonacea: Subergorgia etc.
Tridacnidae: Tridacna gigas (indo-pacific only)
Cypraeidae: Cypris sp.
Pisces: Pomacanthidae, Chaetodontidae, Ephippidae, Mobulidae, etc,
Fig. 44 Reef Slope
Reef Terrace: as the name implies, the Reef Terrace is a relatively flat
surface of the reef which extends from 10-15m water depths offshore
of the reef crest. In the Caribbean, this environment is dominated by
the slim branching coral, Acropora cervicornis, with interspersed
larger head corals of Montastrea species. In this view, the thin sticks
on the bottom are remains of A. cervicornis, which was devastated by
Hurricane Allen in 1980.
Fig. 45 Reef Terrace
Reef Front / Forereef Front / Buttress Zone: the reef front may be the
next part of the reef as land is approached, i.e. front of the forereef.
As the sea floor starts to approach the surface, then enough light
starts to penetrate and supply the energy required for a reef
community to exist. This is divided into two sub–zones, the reef
slope and upper reef slope. The Buttress Zone is a portion of the reef
where environmental conditions are optimal for growth of many reef
organisms (5 - 10m deep). The result of this ideal environment is the
Fig. 46 Buttress zone
development of large coral buttresses which extent seaward and rise
above sand channels. Because this setting is so ideal for reef biota, it
is characterized by the highest diversity of any sites on the reef. The dominant genera present are:
Scleractinians (indo-pacific: Platygyra sp.; altlanic: Diploria sp.).
Pisces: Balistidae, Pomacentridae, Acanthuridae, Labridae, etc.
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Fore Reef (Upper Reef Slope / Seaward Platform): the forereef extends
seaward and downward from the reef crest. It is the most complex of
the reef zones, owing to the large depth gradient over which it occurs.
In many areas, the forereef is organized into a set of en-echelon reef
promontories and sand channels, termed “spur-and-groove”
topography, with fingers of coral formations penetrating into the
ocean with coral sand channels in-between. Spur-and-groove is
Fig. 47a Fore Reef
common in both modern and ancient reefs. The term was originally
coined from Indo-Pacific examples formed by erosion of the algal
rim just below the surf zone. More recently, examples have been
described from the Caribbean that appear to be the result of accretion
by Acropora palmata under the influence of strong wave surge. Both
the coral branches and the intervening sand channels are oriented
parallel to the dominant wave-approach direction (Shinn, 1963;
Roberts, 1974). Hubbard, et al. (1974) proposed that the channels
serve as primary conduits for sediment export from the reef. They
further proposed that spur-and-groove topography will be bestFig. 47b Acropora palmata
developed along windward margins where a barrier exists to
bankward transport, and downslope sediment movement is the only
means of export.
The spurs are typically dominated by large fingered structures of Acropora and massive coral species.
The spur formations provide calmer regions where fleshy green algae, sponges and encrusting corals can
grow. The sandy groove regions support little coral or algae growth because of the strong scouring
surges and tidal run-off running through these grooves. But tough algae such as Halimeda can survive.
The grooves often open out to a region of rubble and coarse sand. This entire zone provides a region
where nutrients are concentrated then transported into the reef flat area by algae growing then becoming
detached.
The Barren Zone is another rigorous, wave
swept environment, but it forms immediately
seaward of the reef crest. Large blocks of coral
are also toppled and pile against the reef edifice
during storms. There are many fewer soft,
fleshy algae in this setting because fish and
other grazers of the reef gobble them up. Corals
have to take on expansive body forms designed
to maximize the exposure to sunlight, but are
not limited to the vast horizontal plates
Fig. 47b Spur and groove system of the fore reef
characteristic of the reef front. The shallower
regions also have more Scleractinians because
of their more robust structure, higher growth rates under intense light and territorial defense mechanisms.
Feather stars, sponges and other suspension feeders expose themselves to intertidal currents on structures
that jut out into the currents, such as gorgonians. Inside overhangs and caverns, azooxanthellae corals,
sponges and soft corals are dominant.
Alcyonaceans: Lemnalia, Lobophytum, Nephthea, Sarcophyton, Sinularia, and Xenia.
Scleractinians: Acropora, Goniastrea, Favia, Favites, Leptoseria, Lobophyllia, Plerogyra, Pocillopora,
Porites, Millepora, and Stylophora.
Zoanthidea: Palythoa.
Pisces: Scorpenidae, Pomacanthidae, Labridae, Acanthuridae, etc.
Reef Crest (Reef Rock Rim): the crest of the main reef is generally emergent in Pacific reefs at low tide, but
may be below the surface in Caribbean reefs. The seaward edge of the reef crest takes the brunt of the
incoming wave energy. Attenuation of wave energy by the reef crest. Roberts (1989) has shown that the
reef can reduce incoming wave energy by up to 97%. As waves
break, water is washed across the reef crest and into the lagoon,
driving lagoonal circulation (Hubbard, et al., 1981). One of the
services provided by reefs is a regeneration breakwater protecting
coastal areas. The change in wave energy results in a different
physical regime leeward of the crest than the reef front. It is the
highest energy zone of a coral reef ecosystem, with very intense light,
Fig. 48a Reef Crest
and intense wave action and surges.
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Corals that live within this zone are typically
very short and fingered or massive in structure
to withstand the strong wave action and as such
don’t have to spread out to capture light. Almost
all surfaces in this zone are exposed to some
light (not just the upper area as in the deeper
reef front zone) so the massive and fingered
structures utilized this fact and are strong
enough to resist the strong currents.
Furthermore, coralline algae cement this region
Fig. 48b Reef Crest
together, forming a solid terraced like pavement.
Often, sand binding algae mats that entrap
sediment.
Alcyonaceans: Lobophytum, Sarcophyton, and Sinularia.
Scleractinians: Acropora, Favites, Montipora and Pocillopora. (Dioploria clivosa in atlantic reefs,
while Leptoria phrygia is dominant in indo-pacific reefs)
Zoanthidea: Palythoa.
Reef Flat: because of the modification of wave forces across the reef crest,
the backreef is an environment of totally different physical processes,
ecology and sediment characteristics. Sediments and rubble from the
reef crest are dumped behind the crest, widening the backreef flat
through time. The outer reefs of the Great Barrier Reef have been at
sea level for nearly 6,000 years. Hence, the wide backreef flats often
exhibit distinctive front-to-back zonation. By comparison, Caribbean
Fig. 49a Rear Zone
reef flats have only recently reached sea level and are narrower. The
organisms of the reef flat must be able to withstand intense ultra
violet radiation, desiccation, high salinities and elevated water
temperature. This zone is divided into two sub-zones, living coral sub
zone and sand sub-zone. Coral cover decreases inward, with sand
covering the inner part of the reef flat.
While zonation is less pronounced, there is a general transition from
branching corals (Acroporidae) and the hydrozoan Millepora near
the front of the crest to sand flats and Thalassia landward.
Amongst scleractinians, it may have a shallow Porites reef flat
immediately behind the crest and numerous small patch reefs in a
Fig. 49a Patch reef
sand apron. The corals are generally well adapted to the high levels
of sedimentation to which they are regularly subjected.
In the Caribbean, the dominant genera include the following Scleractinians: Porites porites and several
other head corals, especially Montastrea annularis, Porites asteroides and species of Diploria.
This entire zone is usually most prolific with Acropora, Actiniarians (anemones), Asteroids (starfish),
Holothurioids (sea cucumbers), Alcyonaceans, and reef fishes. The Rear Zone is a rigorous, wave swept
environment which forms immediately shoreward of the reef crest.
Large blocks of coral are transported to the Rear Zone during storms
where they will be colonized by dense growths of algae. Few other
organisms call this part of the reef home.
Living Coral Sub-Zone: within the living coral sub-zone tongues of the
reef structure penetrate into the lagoon with narrow sand channels inbetween. This is very similar to the upper reef slope. The coral sand
that is present is produced from coralline algae, foraminifers,
Fig. 50 Channel system
calcareous algae, and the breakdown of the reef structure.
Domiant genera of this zone are found among Echinodermata:
echinoids (sea urchins), asteroids (starfish), holothurioids (sea cucumbers) and molluscs.
Scleractinians: Acropora, Pocillopora, Gonipora, Platygyra, Seriatopora, Lobophyllia, Tubipora,
Montipora, Fungia, Goniastrea, Favia, Favites, and Porites.
Pisces: Fistulridae, Serranidae, etc.
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Sand Sub-Zone / Lagoon: reef-building corals often build upward very
close to sea-level. As such, they frequently cause water to be
impounded in a shallow basin between the shore and the reef crest.
This is called the Lagoon Zone, and it is an environment separate
from but still part of the reef system. Lagoon waters may vary greatly
in salinity, temperature and turbidity. This environment is home to a
large community of algae. Gradually the reef structure gives way to
vast areas of coral sand eroded from the main reef structure. Dotted
Fig. 51 Lagoon
throughout this zone are small ‘islands’ of Scleractinians that rise up
out of the sand. In the calmer regions delicate branched corals form
intricate growths. The lagoon is constantly supplied with nutrients and sediment removed from the reef
front and reef rock rim zones, with some lagoons becoming muddy from the accumulated sediment.
Seagrass beds grow on shallow lagoon floors and reef flats and are also very important for coral reef
ecosystems. They act as nurseries for the young of many coral reef fishes. Seagrasses also trap sediment
in their roots, preventing cloudy water from settling on nearby coral reefs. Holothurioids are prolific
inhabitants and constantly rework the surface sediment.
Deeper lagoons with heavy sediments or high turbidity have:
Scleractinians: Cataphyllia, Euphyllia, Gonipora, Leptoseris, Pachyseris, and Montipora.
The island or patch reefs that rise out of the lagoon floor consist of:
Scleractinians: Acropora, Favia, Favites, Galaxea, Goniastraea, Pavona, Pocillopora, Porites,
Seriatopora, Stylophora, and Tubipora.
Spread over the sandy bottom can be found:
Scleractinians: Heliofungia, Fungia, and Herpolitha.
Other families present:
Alcyonaceans: Heliopora, Sarcophyton, Lobophytum, Xenia, Cespitularia, and Sinularia.
Coralliomorpharia: Rhodactis.
Zoanthidea: Palythoa, and Zoanthus.
Cay – Intertidal Zone: this is another high energy zone, with the organisms
that live here adapted to withstand intense ultra violet radiation,
desiccation and high salinities. There is usually water retained in tidal
pools even at low tide. Some corals can survive this harsh
environment completely exposed to the air. Coral cays are formed
when broken down fragments of corals and algae wash onto the Fig. 52 Michelmas cay (north
QLD - AUS)
shallow top of a coral reef. If enough of the sand and rubble collects,
a small island or cay is formed. The exposed areas are homes for
birds and nesting sites for turtles. Gastropods are very common in this zone, and usually the most
conspicuous inhabitants. But there is also a multitude of interstitial sand fauna that extensively inhabits
this zone. Specific family information has yet to be found.
Shore Zone – Beach: finally then comes the beach. Any thing inhabiting
this region is very resilient. Some obvious organisms are molluscs
(mainly mussels that bury themselves in the sand) and decapods
(crabs). The shore zone marks the boundary between terrestrial and
marine environments. In many tropical localities worldwide, this
zone is occupied by dense tangles of mangrove trees. The mangrove
is a very hearty bush which can tolerate salt water. The numerous
prop roots provide habitat for a great diversity of algae, sponges,
Fig. 53 Shore
marine invertebrates.
They also act as nurseries for young shrimp and fishes, including many species of coral reef fishes. Their
falling leaves also provide fish with food and important nutrients. One of the most important functions of
mangroves is that they filter the mud and sediment between the land and the coral reef. When a
mangrove forest is cut down, the mud, silt and fresh water can leak out to the coral reef, which can
smother and kill the corals. Sandy Beaches with trees and plants can also be extremely important for the
health of coral reefs. Similar to the mangroves and seagrasses, the sand acts to filter sediment from the
land, preventing it from smothering the reefs. When sandy beaches and plants are removed, sediment
from storms can run straight into the ocean and onto the coral reefs.
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Reef Communities:
Reef Dwellers and Infillers: major proportion of reef mass is contributed by plants and animals inhabiting the
framework.
A. Framework not only provides living space for organisms but also traps their shells and skeletons.
B. Many reef dwellers enhance trapping action of reef through sediment baffling and binding.
C. Sediment contributed by various dwellers is highly variable in size, shape, mineralogy.
Algae
A. Four major groups: blue-green, green, brown, red.
B. All present on reefs.
C. Calcification occurs mostly in greens and red algae, but even non-calcareous forms act to trap and bind
sediment.
• Green algae (Chlorophyta): major producers of sand, silt, mud; e.g. Halimeda. Penicillus. Udotea.
• Brown algae (Phaeophyta): only Padina calcifies.
• Red algae (Rhodophyta): major role as cementers, e.g. Porolithon, Melobesia; also form sediment
(Goniolithon).
• Blue-Green algae (Cyanophyta): trap and bind sediments to form stromatolites in back reef areas,
lagoons, tidal channels.
Higher plants: turtle grass (Thalassia) forms extensive meadows in back reef, lagoons, and mangroves along
sandy, muddy shores.
A. Dense root mat binds sediment.
B. Blades trap fine carbonate on sticky surface, baffle other sediments.
Animals
A. Protozoa: foraminifera are important contributors.
B. Porifera: sponges contribute spicules, chips from excavation of clionids.
C. Coelenterata: Alcyonarian spicules.
D. Mollusca: major contributors to reef debris: gastropods, bivalves, chitons.
E. Arthropods: crabs, lobsters, barnacles, ostracods contribute calcareous skeletal material.
F. Echinoderms: crinoids, brittle stars, sea stars, echinoids, cucumbers all contribute skeletal debris.
G. Pisces: parrotfish contribute to ultrafine coral sediments, while other herboivores such as damlsefish,
doctorfish, etc. control the algal populationn on the reef.
Fig. 54 Reef organisms
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The Role of Bacteria in Coral Reef Ecology68: coral reefs depend heavily on bacteria in all manner of action.
The majority of bacteria in the water column are free living and feed on dissolved organic matter. These
microbes will process the organic matter in the water with a 30-50% efficiency rate. Pelagic bacteria can
double their populations within one tide change to respond to an increase in nutrient levels. Bacteria
normally compose between 5 and 20% of the total biomass of plankton, either free living in the water
column, or associated with particulate matter. This number represents an even larger planktonic mass
than zooplankton. They are also responsible for up to 30% of the primary production of reefs.
Fig. 55 Microbial food web (left), conventional food chain (right)
The “microbial loop” in the waters above and around a coral reef
revolves around bacteria, organic matter, and the bacteriovores
(zooplankton) such as foraminifers, acantharians, radioarians,
copepods, etc.). This micro-food web is not only important in and of
itself, but is also crucial in the maintenance of the phytoplankton
populations as it is a major provider of N- and P- compounds.
Because of the productivity of the reef organisms, there is a level of
microbial substrate produced by the flora and fauna that allows for
bacterial productivity in the water column above the reef to be
magnitudes of order above that in oceanic waters. As such, they may
be responsible for 40% of picoplankton production and 25% of
microplankton production. In other words, even in the water column,
bacteria are the beginning and end of the plankton that feeds the coral
reef.
The bacterial aggregates associated with particulate matter (detritus,
phytoplankton debris, mucus, etc.) comprise only about 25% of the
total bacterioplankton. Still, they enrich the particulate matter with
their mass (termed “reef snow,” or” marine snow”), becoming a very
important nutrient source for coral reef filter feeders and
planktivores. The important nutrient cycle that centers around
particulate matter and bacteria is termed the “detrital web” (the
nutritional aspect of bacteria to corals will be covered later).
Fig. 56b Foraminifers
Fig. 56c Acantharians
Fig. 56a Eubacteria (left) cyanobakteria (right)
If anyone thought that the importance of bacteria in the water was
impressive, it is nothing short of trival compared to what happens in
the sediments. If the aggregates of bacteria and suspended particulate
matter are not consumed, they have a great chance of settling out on
the sediments of the reef and the lagoon. Much of the waste material,
algae debris, mucus and excess production from the reef is also
drawn towards shore, where it settles on the soft bottoms.
Fig. 56d Radiolarias
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There, it fuels the growth of a diverse community of bacteria, detritivores, and other planctonic flora and
fauna. They mediate the return of organic and inorganic matter back into the food web, provide for the
decomposition of waste and decaying plant and animal matter, and allow for the beginning of new
productivity by providing food and nutrients to algae and microfauna. Frequently, sea grass beds are
found in areas of heavy organic enrichment. These true plants (not algae) are associated with some of the
most highly productive communities on earth. In and around their root structure, microbial production is
as great as in any sedimentary community known. Even the productivity and decompostion abilities of
the terrestrially enriched mangroves owe their effectiveness to bacteria and the community they sponsor.
Perhaps surprisingly, mangroves are typically sources of limiting organic matter which are exported to
the reef, rather than being consumers of it.
Lagoons and sea grass beds depend heavily on the organic matter
produced by the reef, where the productivity of the bacterial
community, by some estimates, equals or exceeds the gross
productivity of the entire reef itself! The upper one centimeter of
lagoon sediments contain as much microbial protozoic microfauna
biomass as all the water column above it. To further emphasize the
immense capabilities of these areas, they are actually nutrient limited!
Here, bacteria are intricately interwoven in the carbon cycle, the
phosphorous cycle, and the nitrogen cycle. Most of the material
Fig. 57a Phytoplankton
exported from the reef is either utilized by the lagoon benthic
communities for their own sustenance, or put back into the food web
after decomposition, remineralization and processing.
It then serves as a food material for the various polychaetes, sponges,
ascidians, corals, bivalves, and plankton that inhabit the reef. A
relatively small portion is either lost to the atmosphere or washed
back into oceanic regions. However, the ultimate regeneration of
nutrients is in their uptake into the reef community for growth and
reproduction, They may also be indirectly incorporated into the
nearly permanent reef structure itself by sustaining the metabolism of
Fig. 57b Zooplankton
the hermatypic corals.
In summary, bacterial action and productivity is absolutely essential
to the reef environment, and provides, arguably, the largest role in its
success. Still, the primary nutrient which limits the bacterial
populations is carbon. Adequate sources of carbon are largely
provided by the success of the coral community. Once again, these
two groups are wholly dependent on each other, and are inextricably
woven together. The denser the coral growth, the more abundant the
microbial growth. The denser the microbial growth, the more
abundant the corals.
Fig. 57c Nekton
Fig. 57d Trophic levels
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Algal communities on the reef65:
algae comprise a grouping of very diverse photosynthetic organisms whose relatively simple vegetative
structure is called “thallus”. They are distributed in several lineages (divisions) which have evolved
independently from each other. In simple terms, we identify a “red lineage” with the red algae or Rhodophyta, a
“brown lineage “ with in particular brown algae or Fucuphyceae, and a “green lineage” grouping together
“green algae” or Chlorophyta, mosses (Bryophyta), ferns (Pteridophyta), gymnosperms (Pinophyta) and
flowering plants (Magnoliophyta). As for blue-green algae, they are grouped with bacteria and are known as
Cyanobacteria. Algae are autotrophic organisms, which are able to manufacture their own organic molecules
from elements containing carbon and nitrogen. Their energy is obtained from sunlight, which is trapped by the
chlorophyll pigment. Furthermore, certain algae such as Ulva, are capable of directly incorporating organic
substances, while the unicellular algae euglenoids and dinoflagellates capture, phagocytose and digest their
prey. They are basically aquatic organisms, even if some (like the green algae Rhizoclonium) temporarily
colonize exposed habitats.
Division Chlorophyta or green algae: chlorophyta are algae whose thallus
is typically green in color due to chlorophyll a and b pigments that
are dominant in the chloroplasts. However, prolonged exposure to
strong light leads to the synthesis of photoprotecting pigments
(carotenoids) that turns the thalli orange to yellow. This group of
algae which is poorly diversified in temperate waters is in fact rich in
species and forms in tropical waters. Green algae are present in all
aquatic systems, from marine to freshwater habitats. The most
diversified Chlorophyta are Caulerpa and Halimeda. The
Fig. 58 Caulerpa bikinensis
cosmopolitan Ulva and Enteromorpha species abundant in calm
(occasionally eutropicated) waters with variable salinity.
However, Ulva blooms remain relatively infrequent on reefs compared to the "green tides" that they
create in several areas of the world. In French Polynesia and in the Cook Islands, the Boodlea kaeneana
algae can, on certain reefs and in the lagoons, bloom in spectacular fashion during the southern summer.
An overcharge in nutrients linked to growing urbanization, in addition to strong sunlight, is the most
probable hypothesis to explain this proliferation.
Division Phaeophyta (Chromophyta) - Fucophyceae or brown algae:
within the Chromophyta, brown algae are grouped in the
Fucophyceae class, formerly called Phaeophyceae. These are almost
exclusively marine algae. Their color is due to the abundance of
brown fucoxanthin pigments that mask chlorophyll a and c.
Fucophyceae display great morphological diversity, from relatively
simple filamentous forms to the large brown algae (Turbinaria,
Sargassum) whose complex morphology approaches the leafy stems
of higher plants. Brown algae are mainly diversified in cold and
Fig. 59 Lobophora variegata
temperate seas where they form large underwater forests (kelp
forests). In tropical waters they
represent fewer species, but have the largest thalli and form the densest populations.
Division Rhodophyta or red algae: rhodophyta are the most numerous algal
group in tropical regions. They show a particular originality with
their dominant red (phycoerythrins) and blue (phycocyanins)
pigments that mask chlorophyll. The relative proportions of the
different pigments, in conjunction with the shape of the thallus, result
in a range of all imaginable colors from dark brown to light pink,
purple reds and orange tints. Furthermore, within a single species,
color varies according to the exposure to light and often individuals
that grow in strong light display faded colors where orange-yellow
hues dominate due to the strong concentration of photoprotectant
carotenoid pigments.
Fig. 60 Galaxaura fasciculata
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Kingdom Bacteria phylum Cyanobacteria (blue-green algae,
Cyanophyceae, = Cyanobacteria), being autotrophic (actively utilize
sunlight and CO2 to meet their energetic requirements) fundamentally
differ from other groups of algae, since they are categorised as
bacteria. They belong to the most ancient forms of life on Earth.
During the Precambrian era (about 1.5 billion years ago), they builtup rocky formations called stromatoliths, either by the precipitation
of calcium or by the trapping of sediments. Despite their very ancient
origin, we should not consider them as a relic group, on the contrary,
Fig. 61 Phormidium sp.
though discrete, they occupy all types of habitats, even those inaccessible to other organisms.
They are generally microscopic filamentous forms that bore into calcareous substrata, or adhere to each
other to create colonies of strongly variable sizes, shapes and colors. Like red algae, they possess more
blue (phycocyanin) and red (phycoerythrin) pigments that mask chlorophyll a. Despite their former name
of blue-green algae, they are rarely blue but more often red, green with blue, violet, brown, yellow or
orange hues. Most of them have a gelatinous or even sticky texture, owing to mucilaginous secretions,
but this is not generally the rule. In addition to their photosynthetic ability, Cyanobacteria play an
important role in the biosphere by transforming atmospheric nitrogen into nitrates which are directly
used by other organisms. This ability is of fundamental importance on coral reefs, where nutrients are
scarce. Furthermore, Cyanobacteria are for humans choice microorganisms in several branches of
biotechnology, owing to the numerous families of chemical molecules that they manufacture, which
have a potential value. Despite an apparent simplicity in the organization of forms, the taxonomic
identification of Cyanobacteria currently remains difficult and complex.
Division Antophyta: the flowering plants; subdivision: Angiospermae,
class Monocotyledoneae, subclass Alismatidae (Heliobiae); order
Hydrocharitaceae (Thalassia sp, turtle grass) is quite common in the
shallow, sandy areas just offshore. As its name suggests, turtles graze
on Thalassia and can crop it quite close, sort of like goats grazing a
field of grass (the local Exxon company actually uses goats to “mow”
their grass). These fields (we call them beds for some reason) of grass
are also habitats for young fish and invertebrates and so are
considered nursery grounds for the reef and offshore fishery. The
blades of Thalassia are long and strap-like, about 1 cm wide, and can
grow rapidly in length. These plants are Angiosperms, or true
flowering plants. This is in contrast to the other simple reef plants
mentioned above. In addition to flowers, Thalassia (as well as our
other common Angiosperm Syringodium or Manatee Grass) have true
roots and a vascular system for conducting fluids and metabolic
signals such as hormones around its body. The roots of Thalassia
grow quite dense with 0.5cm thick individual roots matted together to
the nearly complete exclusion of the sand!
Fig. 62 Thalassia sp.
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Fauna of reefs - invertebrates (the families listed in the following pages represent only some of the sheer
endless diversity found in coral reefs, and therefore should not be considered as a comprehensive summary).
Other characteristics of sponges include a system of pores (also
called ostia) and canals, through which water passes. Water
movement is driven by the beating of flagellae, which are located on
specialized cells called choanocytes (collar cells). Sponges are either
radially symmetrical or asymmetrical. They are supported by a
skeleton made up of a protein collagen and spicules, which may be
calcareous or siliceous, depending on the group of sponges examined.
Skeletal elements, choanocytes, and other cells are imbedded in a
gelatinous matrix called mesoglea (Gk. mesos, middle; glia, gleu;
=mesohyl). Sponges capture food (detritus particles, plankton,
Fig. 63 sponge anatomy
bacteria) that is brought close by water currents created by the
choanocytes. Food items are taken into individual cells by
phagocytosis, and digestion occurs within individual cells.
Reproduction by sponges is by both sexual and asexual means. Asexual reproduction is by means of
external buds. Some species also form internal buds, called gemmules, which can survive extremely
unfavorable conditions that cause the rest of the sponge to die. Sexual reproduction takes place in the
mesoglea. Male gametes are released into the water by a sponge and taken into the pore systems of its
neighbors in the same way as food items. Spermatozoa are “captured” by collar cells, which then lose
their collars and transform into specialized, amoeba-like cells that carry the spermatozoa to the eggs.
Some sponges are monoecious (individuals produce both male and female gametes); others are dioecious
(sexes are separate). In most sponges for which developmental patterns are known, the fertilized egg
develops into a blastula, which is released into the water (in some species, release takes place right after
fertilization; in others, it is delayed and some development takes place within the parent). The larvae
may settle directly and transform into adult sponges, or they may be planktonic for a time. Adult sponges
are always sessile.
Sponges fall into three main groups according to how their bodies are organized. The simplest sponges
are the asconoid sponges. These are shaped like a simple tube perforated by pores. The open internal
part of the tube is called the spongocoel; it contains the collar cells. There is a single opening to the
outside, the osculum into which all pores converge once the water has been filtered through the collar
cells. The osculum is thus the main outstreaming opening of a sponge. The next-most complicated group
is the syconoids. These tend to be larger than asconoids. They also have a tubular body with a single
osculum, but their body wall is thicker and the pores that penetrate it are longer, forming a system of
simple canals. These canals are lined by collar cells, the flagellae of which move water from the outside,
into the spongocoel and out the osculum. The third category of body organization is leuconoid. These
are the largest and most complex sponges. These sponges are made up of masses of tissue penetrated by
numerous canals. Canals lead to numerous small chambers lined with flagellated cells. Water moves
through the canals, into these chambers, and out via a central canal and osculum.
Fig. 64 asconoid, syconoid, leuconoid sponges
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Sponges are found in virtually all aquatic habitats, although they are most common and diverse in the marine
environment. Many species contain toxic substances, probably to discourage predators. Certain other marine
animals take advantage of this characteristic of sponges by placing adult sponges on their bodies, where the
sponges attach and grow. The chemicals also probably play a role in competition among sponges and other
organisms, as they are released by sponges to insure themselves space in the marine ecosystem. Some of these
chemicals have been found to have beneficial pharmaceutical effects for humans, including compounds with
respiratory, cardiovascular, gastrointestinal, anti-inflammatory, antitumor, and antibiotic properties. Sponges
also provide a home for a number of small marine plants, which live in and around their pore systems.
Symbiotic relationships with bacteria and algae have also been reported, in which the sponge provides its
symbiont with support and protection and the symbiont provides the sponge with food. Some sponges (boring
sponges) excavate the surface of corals and molluscs, sometimes causing significant degradation of reefs and
death of the mollusc. The corals or molluscs are not eaten; rather, the sponge is probably seeking protection by
chemically excavating into the hard structures it erodes. Even this process has some beneficial effects, in that it
is an important part of the process by which calcium is recycled.
Class Calcarea (L. calcarea, limestone) the calcareous sponges; these are
the sponges with calcareous (rather than siliceous) skeletons. Their
spicules are made up of calcium carbonate; they are simple in
structure or may have up to four rays. Members of the Class Calcarea
are small. Most are tubular or vase-shaped, and they can have
asconoid, syconoid, or leuconoid organizations. All species are
marine.
Fig. 65 Leucosolenia sp.
Class Demospongiae (Gk. demos, bond; spongos, sponge): this group
include both fresh water and marine species. Their spicules are
siliceous but not six-rayed, but the spicules in some forms are partly
or completely replaced by skeletal elements made of spongin (a
sponge protein). The canal systems are leuconoid. Demospongiae
includes a large number of species.
Fig. 66 Spongia officinalis
Class Hexactinellida (Gk. hexa, six; aktinos, ray) the 6-rayed sponges; the
Hexactinellida are the glass sponges, so-called due to their siliceous
skeletons. The spicules have six rays and are united to form a
network. The body is usually cylindirical or funnel-shaped. Most
Hexactinellida are syconoid or leuconoid in body organization. All
species are marine and most inhabit deep water.
Fig. 67 Aphrocallistes vastus
Class Sclerospongiae (Gk. scleros, hard; spongos, sponge) these sponges
are sometimes included in the class Demospongiae. They have a
massive calcareous basal skeleton, with the living tissue mostly
within the skeleton (extending outward very slightly). These sponges
have siliceous spicules and spongin fibers like those of the
Demospongiae. Their body plan is leuconoid. They are found in
marine environments, usually in association with coral reefs.
Notorious for their biodegradive capabilities are sponges of the
genera Cliona, Anthosigmella, and Spheciospongia, of the order
Hadromerida, and Siphonodictyon (order Haplosclerida). These
sponges actively bore into the calcareous substrate of both limestone
substrata and precipitated CaCO3 of scleractinian corals.
Fig. 68 Sclerospongia sp.
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Phylum Mollusca73: the name Mollusca (from the Latin mollis meaning soft), was first used by the French
zoologist Cuvier in 1798 to describe squids and cuttlefish, animals whose shell is reduced and internal, or
entirely absent. It was only later that the true affinities between these species and other molluscs, such as snails
and bivalves, were fully recognized.
The molluscs are a very successful group. If success is measured in terms of number of species and variety of
habitats to which they have become adapted, then molluscs are one of the three most successful groups in the
animal kingdom. Over 160,000 species have been described, of which around 128,000 are living and about
35,000 are recorded as fossil species.
Molluscs are found in nearly all habitats. In the sea they occur from the deepest ocean trenches to the intertidal
zone. They may be found in freshwater as well as on land where they occupy a wide range of habitats. Thus,
during their evolution, they have become adapted to living in nearly all available habitats.
The phylum Mollusca is normally divided into 8 orders of very unequal importance; the most important class of
living molluscs is the Gastropoda comprising more than 80% of all living mollusc species. Although the
Cephalopoda still contains a number of living species, fossil evidence suggests that they were once far more
abundant than they are today.
Class Polyplacophora (Gk. poly, many; plax, plate; pherein, to bear) order Chitonida, family Chitonidae: the shell is composed of eight
overlapping plates or valves. These are joined to each other on the
outer margin and undersides to the girdle, a thickened part of the
mantle. Scales, spines or bristles may be present on the girdle. Since
the plates allow flexibility, the animal is able to mold itself to uneven
surfaces or roll up in a ball to protect its soft under parts. Chitons are
small mollusks that are common in all rocky shores of the tropics.
They are nocturnal and move around the rocks at night feeding on
algae. Their strange appearance is reminiscent of the ancient Fig. 69 Acanthopleura granulata.
trilobytes of prehistoric times. They are commonly introduced into
the home aquarium with live rock.
Class Gastropods73 (Gk. gaster, belly; pous, foot): the intertidal zone is the high energy zone, thus,
organisms living here are adapted to withstand intense ultra violet radiation, desiccation and high
salinities. There is usually water retained in tidal pools even at low tide. Gastropods are very common in
this zone, and usually the most conspicuous inhabitants. The sandy bottoms of the lagoons are often in
deeper waters, covered with a mucous film rich in bacteria or of a carpet of Cyanobacteria where tufts of
filamentous red algae such as Polysiphonia, Ceramium mingle. It is a hotspot for grazing and browsing
fauna and their predators.
Family Strombidae are one of the more well known of herbivorous molluscs. The
shells of this Family fall into six quite distinct Genera, each having a popular name;
e.g., Strombus (“conches”), Lambis (“spider shells”), Terebellum (“torpedos”),
Tibia (“shinbone shells”), and Varicospira (“beak shells”). Taxonomically they
belong to the class Gastropoda, subclass Prosobranchia, order Caenogastropoda,
Fig. 70a
superfamily Strombacea, family Strombidae
Strombidae
Family Muricidae (predative murex) encompass a diverse and distinct group of
worldwide mollusks consists of five subfamiles, which are then further subdivided
into more than 90 genera. Taxonomically they belong to the class Gastropoda,
subclass Prosobranchia, order Caenogastropoda, superfamily Muricacea, family
Muricidae.
Family Cassidae (helmet shells, bonnets, helmschnecke) are a relatively small
group of marine mollusks, but include some of the largest molluscan species.
Fig. 70b Muricidae
Cassida cornuta, the type species of the genus, is probably the largest. The family
consists of two subfamilies and eight genera according to the most current
literature. The Cassidae inhabit tropical and temperate oceans from intertidal to
subtidal depths. As tropical Cassidae secret acidic mucus, they have been observed
to feed on sea urchins.
Family Volutidae (walzenschnecke) are a large family of extremely diverse
mollusks. The Volutidae also vary greatly in size. Some species rarely exceed a few Fig. 70c Cassidae
cm in length and others are among the largest known species of marine mollusks.
As fast crawlers, all of them are carnivorous, feeding on small marine invertebrate
animals.
Fig. 70d Volutidae
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Family Cypraeidae73 has about 200 living species. The basic shape of the shell is
the same in all species. A very deep coating of enamel on the outer surface gives
the shell a brilliantly polished appearance, naturally. In life, two lobes of the
cowrie’s mantle extend out and over the dorsal surface of the shell, meeting at
midline, and they continually deposit enamel while protecting the shell from
abrasion. Interestingly, the mantle has a totally different color pattern than the shell. Fig. 70e Cyprea
If startled or touched the cowry can suddenly change colors by withdrawing its
tigris
mantle completely inside the shell, thus confusing a predator.
Family Turbinidae73 includes also star shells and are rather unique in being
markedly flattened and in showing a lenticular edgewise appearance. Everwidening whorls leave a deep umbilicus open to the tip of the spire, which can
accommodate a beehive shaped operculum that is chitinous (horny) rather than
Fig. 71a
calcareous. The mollusc lives in shallow sands and is fairly widely distributed in
Monodonta
the warmer waters of the West and East coasts of North and South America, and in
turbinata
the Indo-Pacific regions. Shells of the genus, Heliacus, more resemble those of the
Trochidae family. The operculum is quite different in being a chitinous spiral of
several turns.
Turbo setosus is a commonly found species of the reef crest; with its robust shell it
is perfectly adapted to the rough conditions at the luvward side.
Fig. 71b Turbo
Taxonomically they belong to the class Gastropoda, subclass Prosobranchia, order
setosus
Archaeogastropoda, superfamily Trochacea, family Turbinidae.
Family Cymatiidae (giant triton): Charonia tritonis has been historically used by
humans as a signal horn and today is a rare but questionable collectors item. Its
populations have been declining through massive exploitation. The triton is
immune to the sea stars toxin (e.g. Acanthaster planci = Crown of Thorn) which to
humans causes painful stings which last for hours and skin lesions not healing for
months. During the day the triton rests hidden in the reef with a lid closing its shell.
At night it roams the reef and finds the sea star by using its sense of smell. With it
feelers and well developed eyes the triton evaluates the crown of thorns for an
attack. The triton can move faster than the sea star in case it attempts to escape. The
triton pushes its proboscis and front part of its shell under the sea star and turns it Fig. 72 Charonia
over onto its back. Then the triton proceeds to devour the sea star entirely, spines tritonis feeding on
A.planci
and all. The relatively large weight of the giant triton locks the sea star in place and
prevents it from fleeing. After 2 or 3 hours the triton has completely swallowed the
poisonous mass of spines. Unfortunately, the tritons cannot effectively control mass outbreaks of the
crown of thorns sea star even if they were in normal densities on untouched reefs.
Feeding habits of A.planci (see also bioerosion, p.58/59): it preys exclusively on coral by everting
stomach. It is normally uncommon on Pacific reefs crown-of-thorns is subject to massive population
explosions in which hoards sweep across a reef. A.planci prefers branching, rapidly growing corals, but
will take massive forms after depleting others. Affected reefs will be totally devastated by outbreaks,
leaving bare framework open to bioerosion and physcial destruction; e.g., Guam, 1969: 90% of living
corals killed off along 38 km of coastline down to 65 m. Recovery of devastated reefs is slow, 20-40 yr.
Hypotheses for Acanthaster outbreaks range from human interference (removal of triton shell or puffer
fish predators; excavation and dredging of reefs, opening sites for larval settlement) to natural, cyclic
phenomenon. Control by success of larval recruitment, dependent on nutrient input from terrestrial
runoff, which triggers plankton blooms.
Order Opisthobranch (Gk. ophisten, behind; branchia, gill): gastropods comprise a large and diverse
group of marine snails and slugs, including some of the most beautiful and most specialized forms. The
most recognizable to non-specialists are perhaps the sea slugs, or nudibranchs, and the pelagic sea
butterflies, or pteropods. Morphologically intermediate between the more traditional snails and the shellless nudibranchs are the “bubble-snails,” belonging to the Order Cephalaspidea.
The adult stage in nudibranchs has completely lost both the shell and operculum.
They share this character with the plant-eating sacoglossa or ascoglossa, which are
not covered here. The loss of the shell has allowed a diverse array of body forms
within this order. The Nudibranchia is divided into the following four suborders;
the Dendronotacea, Doridacea, Arminacea and Aeolidacea. The name “nudibranch”
means naked gills and the tail end of most sport a tuft of feathery objects that are
the exposed gills that allow oxygen exchange. The front end is set off by a pair of
feelers (rhinophores) and are exquisitely sensitive chemical receptors for prey, Fig. 73 Phyllidia
dangers or potential mates.
coelestis
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Class Bivalvia (L. bi, two; valva, valve) includs scallops, clams, mussels, and oysters; they comprise the
second largest group of mollusks, yet are historically understudied relative to other mollusks. They are
mega-diverse, comprising 8000-20,000 recent species in a wide variety of ecological and trophic niches.
Bivalves are significant economically and ecologically: important aquaculture candidates, endangered
and extinct species (freshwater mussels, Unionidae), and introduced pest species (zebra mussels).
Despite their importance
our understanding of bivalves as living invertebrate animals is fragmentary. Like
other species of mollusks, many species are known from empty shells alone. More
distant mollusc relatives are snails, sea slugs, octopus, squid, cuttlefish and
chambered nautilus.
Family Tridacnidae (giant clams) are molluscs, they belong to the group that
includes other bivalves, like the oysters, scallops, mussels, and other clams. There Fig. 74a Tridacna
are seven species of giant clams found in the tropical Western Pacific and Indian
sp.
Oceans. The smallest species reaches only 15cm in length, while the largest
species, Tridacna gigas, may grow to more than 1 m and weigh up to 300
kilograms.
This extremely colorful species of scallop is found in the Caribbean, and reaches a
size of 8cm. They have an amusing method of propulsion which involves clapping
their shells together to jet propel themselves through the water. They are like most
Fig. 74b Lima
of the bivalves filter feeders and feed on plankton and other nutrients in the water.
scabra.
Cass Cephalopoda (Gk. kephale, head; pous, foot);
order Octopoda69 (Gk. octo, eight; pous, foot) devilfish (kraken)
have rather short, compact bodies and only eight arms; no trace of the
missing second arm pair remains even during embryonic
development. All species are active at night, whereas many species
are benthic (bottom-living) and crawl over the ocean floor with the
mouth facing the substratum. Others alternate between a benthic and
a pelagic (free-swimming) habitat and some species are completely
pelagic. The two suborders of Octopoda are very different in
Fig. 75a Octopoda
appearance but there is little doubt that it is a natural group as the
monophyly of the Octopoda is supported by a large variety of
characters.
The Cirrata is a group of deep-sea octopods commonly known as the
“finned octopods” due to their large, wing-like fins. The Incirrata
contain the common (benthic), shallow-water octopods as well as
many deep-sea benthic and pelagic species.
The most famous of these octopuses is the blue ring octopus
(Hapalochlaena Iunulata, about 6 cm). The salvia of blue-ringed
octopuses contains a powerful nerve toxic that blocks nerves from
transmitting messages to the brain. The victim’s voluntary muscles Fig. 75b Hapalochlaena maculosa
(involuntary muscles such as the heart, iris and gut lining continue to
function) are paralyzed (people die from lack of oxygen).
If mouth to mouth resuscitation is given, the victim recovers fully. Blue-ringed octopuses are shy and not
aggressive, they tend to avoid people (they are not their natural prey – much too big!).
Order Nautiloids (Gk. nautes, sailer; eidos, form) family Natiloidea
(nautilus): the chambered or pearly nautilus is a member of the
cephalopod class of the mollusks. The nautilus is a “living fossil”
whose close relatives date back 100’s of millions of years into
geologic history. The life and habits of the nautilus are, for the most
part, a mystery, although a great deal has been learned about the
nautilus in recent decades. For many years the nautilus was thought
to be a rare deep water species, but recently they have been
discovered in large numbers on Indo-Pacific reefs. They are nocturnal
animals, swimming around the reef at night in search of small fish
and shrimp.
Fig. 76 Nautilus macromphalus
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Phylum Annelids71 (ringed worms): the annelid worms are thought to have evolved from a primitive coelomate
worm-like ancestor which developed metameric segmentation. The development of a coelom conferred many
advantages, including acting as a hydrostatic means of locomotion. However, in the ancestral coelomate the
force of muscle contractions in one area was carried throughout the body and so precise control of body
movements was not possible. The phylum Annelida is divided into 3 classes:
Polychaeta (bristleworms, mainly marine) Oligochaeta; (earthworms, mainly terrestrial) and freshwater
Huridinea (leeches, mainly freshwater but with marine and terrestrial species of these); the polychaetes are
thought to be closest to the ancestral form, (although, as we shall see, some of the polychaetes are highly
specialized).
The sea worms are a large and varied group of animals belonging to the annelids. They are segmented worms,
and all bear at least some resemblance to the common earthworm. In the ocean, however, the worms have
evolved many different appearances. One of the more interesting varieties are the tube worms. These animals
form a hard-shelled tube that provides them protection. The feather duster worms have a series of feathery
tentacles on top that are used to filter nutrients from the water. When threatened by predators, they quickly
withdraw deep into their tube homes. Another species, the Christmas tree worm, has a very ornate arrangement
of feeding tentacles that can be found in a wide variety of bright colors. Some sea worms, such as the bristle
worm, wander the sea floor with a covering of tiny bristles that can deliver a painful sting if threatened.
Family
Terebellidae (fanworms, spagettiwurm): these meter-long
polychaets are highly adapted deposit feeders and occur in soft
bottom communities but are more widespread in temperate and coral
reefs as crevice fauna, and associated with seagrass beds. They are all
surface deposit feeders and may be highly selective. They have
brightly colored feathery plumules. They are actually short and
plump worms with sedentary habits. They have no proboscis as their
food is collected by specialized feeding devices which evolved as
part of the head. Only suitable sized particles are ingested while
others are rejected through the mouth. They can extend their grooved
buccal tentacles over substratum for a distance equal to the length of
the body. Mucus secreted by the tentacles are used to prey upon
living, planktonic organisms. They live in quiet places like the
lagoons, rock pools or crevices where organic particles settle and are
picked up by these sticky tentacles. Being tubicolous, the adult build
fragile tubes out of sand, mud, shell fragments and sponge spicules
with mucus heavily incorporated into them. The majority of the
Fig. 77 Terebellidae
tubicolous species are in contact with solid surfaces provided by shell
hash, gravel, seagrasses, algae and sponges. Their tubes are found under large rocks or in cracks and
crevices.
Family Spirorbidae (christmas tree worms, Spirobranchus giganteus) have
an elaborate crown of spirals of feather-like tentacles/gills surrounds
their tree-shaped body. When the worm is attacked or approached,
the gills snap in and close a calcified trap door (operculum) to the
tube to protect the actual worm from danger. At the base of their fans,
the worms have a collar folded over the rim of the tube. As the worm
grows, this collar adds layers upon layer of calcium salts embedded
in slimy protein cells. The Spirorbidae tubes are small, white, and
tightly coiled spirals. The size of the calcareous tubes range from less
than one mm to several cm in diameter. Their gills range from 3-6cm
Fig. 78 Spirobranchus giganteus
length. The photo illustrates the “Christmas Tree Worm”, a passive
residing in a Porites colony
member of the reef community. These worms actively extend their
feeding structures to filter particulate matter from passing water
currents. If disturbed, they rapidly retreat into their “worm tubes” which are passively constructed
alongside the living coral
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Family Sabellidae (tube worm, feather duster, grosser röhrenwurm): worms
with smooth tapering cylindrical bodies living in tough non
calcareous tubes. The prostomium and peristomium are fused and
have developed into a tentacular crown (bi-pinnate radioles) that
often obscures a pair of grooved palps. There is no operculum. The
peristome is often developed into a collar surrounding the base of the
radioles. Ciliated cells on the branchial crown filaments secrete
mucus that collects captured particles such as detritus and bacteria.
Mucus particles are formed and move down the branchial filaments
to the mouth at the base of the crown. Along the way the particles are Fig. 79a Sabellastarte magnifica
sorted for the correct size to be eaten. The body is clearly divided into
thorax and abdomen. Chaetae are winged capillaries and uncini. Note
that the tentacular crown is easily lost during collection and
preservation. Its leathery tubes reach a length of 15cm, with a plume
of feathery brown and white gills about 10cm long. The large-eyed
Feather Duster worm can be found growing in leathery tubes
approximately 10cm long. The feathery gills are usually orange-red
to reddish-brown in color with white tips.
Fig. 79b Potamilla reniformis
Family Amprinomidae (bristleworm, fireworm): the fireworms get their
name from the extremely painful stings they can deliver from the
feathery bristles along their sides. After the sting, the pain and itching
can last for weeks. Fireworms can usually be found under rocks and
coral heads on the reef and generally reach a size of 30cm in length.
In life it is pink with conspicuous white setae which detach readily
and cause severe irritation, forming a protective mechanism. Some
people have had serious infections develop after being stung by such
fireworms.
Fig. 80a Eurythoe complanata
Fig. 80b Hermodice carunculata
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Phylum Arthropods72 (Gk. arthro, joined; poda, feet): the world of the crustaceans is a world of bizarre shapes
and adaptations. Crustacean arthropods dominate the oceans; so much so that, with the exception of only a few
specialised species, no other arthropods are found in the marine environment. This group of animals is probably
best-known for their hard outer shell. As the animal grows, this shell must be removed and discarded. Once this
takes place, the new shell takes time to harden. During this period, the animal is without its primary means of
protection and vulnerable to attack from predators. But they have an impressive arsenal of weapons at their
disposal. The claw of many crustaceans is capable of exerting great pressures. Some even have the unique
ability to produce a deafening miniature sonic boom with which they stun their prey. The mantis shrimp can
even break the glass of an aquarium or split a man’s thumb to the bone with one strike.
Order Decapoda (Gk. deka, ten; pous, foot): a worldwide order of crustaceans (over
8500 species), with five pairs of thoracic appendages - anterior pincers and four
pairs of walking legs. They include the shrimps and prawns (suborder: Natantia,
“swimming forms”) and lobster, crayfish, and crabs (suborder: Reptantia, “walking
forms”). Class Malacostraca.
Family Majidae (arrow crab): these rather bizarre looking creatures get their name
Fig. 81a
from the triangular or arrowhead shape of their bodies. Their long legs gives them a
Stenorhynchus
spider-like appearance. They can reach a leg span of about 15cm, and are notorious
seticornis
for pulling feather duster worms out of their tubes with their long claws.
Family Diogenidae (hermit crab, einsiedler krebse): the Hermit Crab is a curious
species that carries its home around on its back. Because the crab’s abdomen is soft
and vulnerable, its uses discarded snail shells to protect itself. As the crab grows
larger, it must continually seek out larger shells. Hermit crabs are adept scavengers,
and will feed on just about anything they find.
Fig. 81b Dardanus
Family Hippolytidae (cleaner shrimp, putzer garnele): the Cleaner Shrimp gets its
megistos
name from its behavior of cleaning parasites and damaged scales from many
species of fish, including moray eels and large groupers. Although it would make a
tasty morsel, the shrimp is allowed to clean inside the fishes’ mouth in complete
safety with no danger of being eaten. They are typically found in small caves in
sheltered areas of the reef setting up cleaning stations for passing fish. These
cleaning stations are manned by a large group of the shrimp.
Fig. 81c Lysmata
Family Grapsidae (purple shore crab) is commonly found on the open rocky
amboinensis
seashores of the pacific coast of North America. It has a purple and red shell with a
white underbelly, and grows to about 5cm in length. This small crab can be seen
scavenging the seashore where it feeds on algae and dead animal matter.
Family Porcellanidae (porzellankrabbe, anemone crab): this small, colorful crab
with a porcelain-like shell. Like the Clownfish, this crab has developed an
immunity to anemone stings. This crab is usually found within the stinging
Fig. 81d
tentacles of a number of anemone species where it uses its large well-developed
Hemigrapsus
claws to keep clownfish from stealing its home.
nudus
Order Isopoda (Gk. iso, equal; pous, foot): within specific habitats, the isopods
frequently constitute a major component of the energy cycle, fulfilling roles of
micrograzers, micropredators, parasites, and detritivores. In general, the suborders
(Phreatoicidea, Asellota, Microcerberidea, Calabozoidea, Oniscidea, Valvifera,
etc.) are herbivores or herbivorous scavengers, whereas the other suborders
(Flabellifera, Epicaridea, Gnathiidea, etc.) are carnivores, predators, and parasites.
Almost every animal of the coral reef ecosystem contains one or more parasite on
or in its body.
They attach almost anywhere on their hosts, most notably to the skin,
gills, and fins. Isopods tend to pierce into their hosts and feed on
blood and tissue fluids, causing lesions. Fortunately, there exist
species such as the cleaner wrasse, which swims over the entire body
of the host fish, picking parasites from the scales.
Isopod feeding habits are extremely diverse. In some areas of the
world, isopods emerge from the benthos in large numbers at night to
prey on (and frequently kill) diseased or injured fishes, as well as
attacking fishes caught in commercial traps or nets (Stepien & Brusca
1985).
Fig. 82 parasitic isopod
Fig. 81e
Neopetrolisthes
ohshimai
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Phylum Echinodermata74 (Gk. echinos, spine; derma; skin): the echinoderms are a group of animals that
includes starfish, urchins, feather stars, and sea cucumbers. They are simple animals, lacking a brain and
complex sensing organs. Echinoderms are characterized by their radial symmetry and a central mouth. The
coelom of the animals in this phylum is made from the digestive tube, not from cell masses. Therefore,
echinoderms are deuterostomes. Although a sea urchin looks round and has developed extremely sharp spines
as a means of protection, closer inspection reveals that it is nothing more than a starfish with its legs wrapped
inwards to form a sphere. Echinoderms have an endoskeleton, made of 95% calcium carbonate. Another
hallmark of the echinoderms is hard, spiny skin. This is a common feature, but not always apparent in
echinoderms. The uniting feature of echinoderms is a water-vascular system. This is a system of canals
branching throughout the body that branch into many sections called tube feet. There are at least 2,000 tube
feet, which can penetrate the body wall and skeleton in places called ambulacral grooves, in most echinoderms.
These tube feet, and in many echinoderms arms and even organs, can be regenerated. The echinoderms are
found in a stunning variety of shapes and colors, and are found decorating reefs around the world. Some of
these animals are carnivorous, feeding on corals and scavenging the ocean floor. Certain species of starfish
actually extend their stomachs into their unwary victims in order to digest them. The feather stars and sea
cucumbers are mainly filter feeders, catching what ever they can find floating in the ocean currents. All of the
echinoderms move around with the use of thousands of tiny tube feet, many of which have suction cups on the
ends.
Class Crinoidea (Gk. krinon, lilly; eidos, form): the sea lillies, feather
stars are the most primitive and oldest class. They consist of both
deep sea lilies and tropical feather stars. These represent the earliest
echinoderms, and are probably similar to a common ancestor of the
entire phylum. The species that make up this phylum do not show
body segmentation, and are radially symmetrical when fully grown
but bilaterally symmetrical in the larvae stage. Almost all of the
species are marine, although a few can live in brackish water.
Fig. 83a Crinoidea
Family Mariametridae (feather stars) is an unusual species that
looks more like a plant than a starfish. It ranges in color from brown
to orange, yellow, and black. Like the basket star, the feather starfish
is a filter feeder. It is nocturnal, and at night it can be found with its
long arms unfurled where it filters plankton from the water.
Fig. 83b Lamprometra palmata
Class Ophiuroidea (Gk. ophius, serpent; eidos, form) brittle stars
(schlangensterne): these species have very flexible arms that are used
for walking. These arms lack ambulacral grooves, differing the brittle
stars from the sea stars. The species that make up this phylum do not
show body segmentation, and are radially symmetrical when fully
grown but bilaterally symmetrical in the larvae stage. Almost all of
the species are marine, although a few can live in brackish water.
Fig. 84a Ophiuroidea
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Class Echinoideae (Gk. echinos, spiny; eidos, form): sea urchins have a
number of predators on coral reefs as well, including molluscs and
fish. It is difficult to imagine a predator being able to penetrate the
terrifying arsenal of poisonous spines of Diadema urchins, but there
are several fish which can make a meal on this unlikely prey,
including porcupine fish (Diodon hystrix), and several triggerfish.
Some of these fish are able to penetrate the spines, but most feed by
turning the urchin over, and going into the shell through the soft
tissue surrounding the mouth. For example, the Indo-Pacific titan Fig 85a Diadema setosum of the
triggerfish (Balistoides virescens) is able to flip an urchin over by
Indo-Pacific
ejecting a strong jet of water while the urchin is relaxed.
While some urchins are active during the day, and some during both
day and night, most tropical urchins are nocturnal foragers. On IndoPacific coral reefs, it is not uncommon to find sea urchins such as
Diadema taking shelter in crevices, or forming defensive
aggregations during daytime, but coming out at night and dispersing
over the reef to feed on algae and sea grass. Some of the slate pencil
urchins seem to disappear entirely from the reef in the day, but
appear again as if by magic at night. Sea urchins play an important Fig. 85b Diadema antillarum of
role in the ecology of coral reefs. A variety of species inhabit the reef
the Atlantic
environment, each one occupying a slightly different habitat, or
feeding on a slightly different type of food.
Their presence, together with the presence of a group of herbivorous
fishes, helps to keep the coral reef from becoming overgrown and
smothered with algae. Without this group of herbivorous fishes and
sea urchins, coral reefs as we know them, could not exist. However,
when reefs become overfished as a result of poor or non-existent
management practices, urchin populations may explode unchecked.
At such artificially high densities, urchins may graze in habitats
normally protected from grazing. They may also graze on live coral,
Fig. 85c Heterocentrotus
or damage and kill live coral in their movements in search of a
mammillatus
limited food supply.
Populations of tropical Diadema urchins expanded on some reefs of the Egyptian Red Sea during the
1970’s, and destroyed large areas of coral, completely altering the reef environment. It is thought that the
collection of porcupine fish for the curio trade may have depleted populations of this predator, and that
this in turn allowed the urchin populations to explode. Nature is rarely that simple, but it does seem
likely that the removal of a suite of predators from the reef may have played a role in the urchins’
unchecked increase. Similar increases in urchin abundance have also been recorded on Caribbean reefs,
and on reefs in the Comores.
Class Holothuroidae (Gk. holothourion, sea polyp) sea cucumbers,
(seegurken, seewalzen) are an abundant and diverse group of wormlike and usually soft-bodied echinoderms. They are found in nearly
every marine environment, but are most diverse on tropical shallowwater coral reefs. They range from the intertidal, where they may be
exposed briefly at low tide, to the floor of the deepest oceanic
trenches. Considerable diversification has occurred since then with
about 1400 living species in a variety of forms. Some of these are
Fig. 86 Synapta maculata
about 20cm in length, though adults of some diminutive species may
not exceed a centimeter, while one large species can reach lengths of
5m (Synapta maculata).
Several species can swim and there are even forms that live their entire lives as plankton, floating with
the ocean currents. Economically, sea cucumbers are important in two main ways. First, some species
produce toxins that are of interest to pharmaceutical firms. Some compounds isolated to date exhibit
antimicrobial activity or act as anti-inflammatory agents and anticoagulants. Furthermore, the sticky
Cuvierian tubules are placed over bleeding wounds as a bandage.Second, as a gourmet food item in the
orient, they form the basis of a multimillion-dollar industry that processes the body wall for sale as
Beche-de-Mer or Trepang. However, the high value of some species, the ease with which such shallowwater forms can be collected and their top-heavy age structures all contribute to over-exploitation and
collapse of the fisheries in some regions. Fishermen in the Pacific islands use the toxins, some of which
act as respiratory inhibitors, to entice fish and octopus from crevices so that they may be more easily
speared.
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Class Asteroidea (Gk. aster, star; eidos, form): unlike the superficially
similar brittles stars (Ophiuroidea), true starfish have no sharp
demarcation between arms and central body, and they move using
tube feet rather than wriggling movements of the whole arms. Most
starfish are predators, feeding on sessile or slow-moving prey such as
mollusks and barnacles. The aptly named crown-of-thorns starfish,
Acanthaster (shown below), specializes on corals, and may do
considerable damage to coral reefs. Many, but not all, starfish are
able to turn a portion of their stomachs out through the mouth, and
thus digest food outside of the body.
Fromia monolis colorful orange and red starfish is one of the most
common species. Its colorful markings and docile nature make it
quite popular among aquarium hobbyists. This starfish grows to
about 10cm in diameter, and is commonly found in the Indian ocean
near Indonesia where is feeds on small sponges and algae.
The Cushion Star (Oreaster reticulatus) is a thick-bodied species of
starfish with short legs. It ranges in color from brown to orange, red,
and yellow. Its hard shell is covered with raised knobby spines. This
starfish grows to a diameter of 25cm, and is found on the sandy
bottoms.
The infamous crown-of-thorns starfish (Acanthaster planci) grows to
over 30cm across and has 10-20 arms. It is well known for its
voracious appetite for live hard-corals. At various times it has been
blamed for the killing of large portions of reefs in parts of the pacific
ocean, including a large portion of the Great Barrier Reef of Australia
during the 1960’s. It is so despised that many scuba clubs organize
“starfish hunts” in which these starfish are rounded up in an effort to
save reefs from destruction. These starfish should be handled
carefully, since the long, sharp spines are mildly venomous and can
inflict painful, slowly healing wounds.
One explanation for local population explosions of these destructive
starfish could be the collection of this starfish’s natural enemy, the
Triton Trumpet (Charonia tritonis). For this reason trumpet shellfish
(if alive) should never be collected by divers and are often protected
by law, because of their importance to reef ecology.
Fig. 87a Fromia monolis
Fig. 87b Oreaster reticulatus
Fig. 87c A.placi shown here to
feed on Porites sp.
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Some other reef-fauna not mentioned so far: ecologically speaking, coral reefs are diverse places, containing
22 of the 23 animal phyla found on the planet. Symbiotic relationships are common and add to the complexity
of species interactions. Coral reefs are among the most productive habitats, producing 2,000 decagrams of
carbon per square meter per year, and the oldest, 400 million years.
Phylum Platyhelminthes (Gk. platys, flat; helminthes, worm): usually
they are microscopic animals that live in numerous environments
including the sea. Many species are parasitic and these are sometimes
known as flukes. unsegmented worm-like animals with one opening
to ingest food. The flatworms have flattened bodies and look more
like chewing gum as they forage for food on the rocks.
Class Turbellaria (L. turbellae, disturbance) mostly free-living and
free-swimming for the whole of their life ciliated flatworms. They are
found in a wide range of bright colors. These colors serve as a
warning to potential predators because the worms excrete a foul- Fig. 88a Pseudoceros splendidus
tasting mucus. The Red-rim Flatworm Pseudoceros splendidus
reaches a size of approximately 3-5cm in length.
Gliding over the rocks and seaweed in the shallow sea, the Candy-striped Flatworm, Prostheceraeus
vittatus, is occasionally seen by divers, and only very rarely reported by rockpoolers under rocks on the
lower shore. The Candy-striped Flatworm is an active predator. It only grows to 50mm in length, but this
is large for a planarian or flatworm, because most of them are parasitic on a variety of other animals
including molluscs, crustaceans and fish in the sea.
Phylum Ectoprocta (moss animals) or Bryozoa66: refers to the mooslike
appearance of many of he colonies. Some bryozoans encrust rocky
surfaces, shells, or algae. Others, like the fossil bryozoans shown
here, form lacy or fan-like colonies that in some regions may form an
abundant component of limestones. Bryozoan colonies range from
millimeters to meters in size, but the individuals that make up the
colonies are rarely larger than a millimetre. Each body, or zooid, has
a circular horseshoe-shaped lophophore and is largely covered with a
chitonous cuticle that usually encloses a gelatinous, leathering, or
calcified exoskeleton. Bryozoans are considered nuisances by some:
over 125 species are known to grow on the bottoms of ships, causing
drag and reducing the efficiency and maneuverability of the fouled Fig. 88b Ectorocta durig feeding
ships.
Bryozoans may also foul pilings, piers, and docks. Certain freshwater species occasionally form great
jellylike colonies so huge they clog public or industrial water intakes. Yet bryozoans produce a
remarkable variety of chemical compounds, some of which may find uses in medicine.
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Phylum Chordata75,76,77: chordates are defined as organisms that possess a structure called a notochord, at least
during some part of their development. The notochord is a rod that extends most of the length of the body when
it is fully developed. Lying dorsal to the gut but ventral to the central nervous system, it stiffens the body and
acts as support during locomotion. Other characteristics shared by chordates include the following (from
Hickman and Roberts, 1994):
• bilateral symmetry
• segmented body, including segmented muscles;
• three germ layers and a well-developed coelom;
• single, dorsal, hollow nerve cord, usually with an enlarged anterior end (brain);
• tail projecting beyond (posterior to) the anus at some stage of development;
• pharyngeal pouches present at some stage of development;
• ventral heart, with dorsal and ventral blood vessels and a closed blood system;
• complete digestive system;
• bony or cartilaginous endoskeleton usually present.
Subphylum Urochordata (Gk. oura, tail; chorde cord)75: the tunicates
include a wide variety and, among other characteristics, are based on
the presence of a larval notochord. The great majority are benthic
sac-like filter feeders in the class Ascidiacea. Most species filter
water by a variety of mechanisms to extract fine planktonic food
particles. Those within two much smaller classes (Thaliacea and
Appendicularia), with some representatives listed here, are unique
among the tunicates in that they have abandoned the benthic
existence in favor of a holoplanktonic lifestyle.
Class Larvacea (L. larva, ghost) or Appendicularia: includes a variety of
Fig. 89a pelagic tunicates
mostly inconspicuous, small pelagic tunicates. The body is formed by
an oval-shaped trunk (often only about 1mm in length) and a longer
tail, which is absent in thaliaceans.
Class Thaliacea (German naturalist Thalius) order Salpida (salps)
include the most commonly encountered pelagic tunicates. Salps can
form massive aggregations of millions of individuals that may play a
significant role in marine ecosystems. They exhibit among the fastest
growth rates of any multicellular organism. A transparent test
encloses the cylindrical body, and may be relatively thick and tough
with projections and keels. Using rhythmic contractions of bands of
circular muscles within the body wall, movement by jet propulsion is
Fig. 89b Clavelina picta
accomplished by regulating the action of sphincter muscles that open
and close anterior and posterior openings.
This also serves to pump plankton-laden water through the body. Salps exhibit a complex life cycle with
alternating aggregate and solitary generations. Aggregates (the sexual gonozooids) develop asexually
from an elongating stolon that buds from an area just behind the endostyle of the solitary individuals (the
oozooid). Individuals within aggregates are hermaphrodites, typically starting as females that are
fertilized by older male individuals from another chain. The resulting embryos (oozooids) then develop
into the solitary asexual phase. There is no larval stage and even before release the young oozooid often
has a developing stolon. In many species only a single embryo develops within each individual of the
aggregate. This method of asexual reproduction enables salps to quickly exploit periods of abundant
food with rapid increases in population density. With few defenses, rapid growth to maturity is the
primary means to avoid predation by heteropods, jellyfish, siphonophores, ctenophores, sea turtles,
marine birds and numerous types of fishes. Hyperiid amphipods and several species of fish also use salps
as traveling homes. Other groups of thaliaceans include the doliolids (order Doliolida) and pyrosomes
(order Pyrosomatida).
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Subphylum Vertebrata (L. verteratus, having a backbone) also known as Craniota; apart from their neural tube
differentiated into a brain and spinal cord, have a vcranium (encapsuled brain);
Class Chondrichthyes75 (Gk. chondros, cartilage; icthys, fish) such as sharks, skates, rays, and chimaeras:
their endoskeleton is entirely cartilaginous and all are carnivorous as exemplified by the great white
shark (Carcharodon carcharias), the principle character in the "jaws" movie serials).
There is perhaps no other animal on earth that evokes more fear in the mind of man than the shark. They
are viewed as vicious man-eaters and are slaughtered the world over in an attempt to "make the seas
safe". But of the hundreds of different species of sharks in the ocean, only a small handful pose any
threat to man. Humans do not appear to be on the menu for sharks. It is thought that most shark attacks
are a case of mistaken identity. A diver in a wet suit looks a lot like a sea lion, a favorite food for some
of the larger sharks. The fact is that more people are killed by lightning each year then by sharks. Public
fear and ignorance of these magnificent animals has led to many species being hunted and killed in large
numbers. They have almost disappeared in some parts of the world.
The Gray Reef Shark (Carcharhinus amblyrhynchos) is one of the
major predators on the reef. Its highly streamlined body allows it a
great deal of speed and maneuverability in the water. The Gray Reef
shark is a very aggressive species, and is commonly seen in the
classic "feeding frenzy" film footage. This shark can be identified by
the black markings on its pectoral and tail fins. In startling contrast to
the gray reef shark, the Whitetip Reef shark (Triaenodon obesus) is a
timid and unaggressive species. This shark is commonly found near
the floor of the reef, where it feed mainly on small fish, octopus,
lobster and crabs. The Whitetip grows to a length of 150cm, and can
Fig. 90a Carcharhinus
be identified by the white markings on the tips of its fins. The Nurse
amblyrhynchos
Shark (Ginglymostoma cirratum) is a very docile and unaggressive
species. It is a sluggish bottom feeder, and it uses its pavement-like
teeth to crush shellfish. The Nurse Shark is commonly seen lying
motionless on the ocean floor. It grows to an average length of
210cm, and is not considered dangerous to man.
The Blue Spotted Stingray (Taeniura lymma) is a beautiful species,
with brightly colored blue spots on its body. It is a relatively small
ray, and can be kept successfully in an aquarium environment.
There are few sites in the ocean as beautiful as the graceful flight of
the Manta Ray (Manta hamiltoni) through the clear, blue waters. This
magnificent animal can have a wingspan in excess of 450cm. Unlike
Fig. 90b Triaenodon obesus
its stingray cousins, the manta ray has no sting. They feed mainly on
plankton and small schooling fish.
The Ornate Wobbegong (Orectolobus ornatus) can be recognized by
its body shape and coloration. It has a broad, flattened head with skin
flaps around the snout margin. The eyes are small and oval (see
bottom image). This species has two dorsal fins which are positioned
posteriorly on the body. The caudal fin has a long upper lobe. The
anal fin is positioned so far posteriorly, it almost looks like a lower
caudal fin lobe. The intricate color pattern of the Ornate Wobbegong
helps to break up the fish's outline. Even when illuminated by a flash
as in the image, the mottled pattern on the tail helps camouflage the
Fig. 90c Ginglymostoma
fish against the sand and algae covered bottom.
cirratum
Fig. 90d Orectolobus ornatus
Fig. 90d Taeniura lymma
Fig. 90d Manta hamiltoni
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Class Osteichthyes76 (Gk. osteon, bone; icthys, fish): the bony fish are the most diverse and numerous of all
vertebrates. They differ from most of the cartilaginous fishes in having a terminal mouth and a flap
(operculum) covering the gills. In addition, most have a swim bladder, which is ordinarily used to adjust
their buoyancy, although among the air-breathing fishes it is attached to the pharynx and serves as a
simple lung. The skin has many mucus glands and is usually adorned with dermal scales. Their jaws are
well developed, articulated with the skull, and armed with teeth. Although the skeleton of most is bone,
that of sturgeons and a few others is largely made of cartilage. They have a two-chambered heart built on
the same plan as the Chondrichthyes (two-chambered with a Conus arteriosus and a sinus venosus). The
sexes are separate, most are oviparous, and fertilization is usually external. There are two subclasses:
subclass Actinopterygii (ray-finned fishes) and subclass Sarcopterygii (lobe-finned fishes).
Family Labridae (Gk. labros, greedy or in L. lipp) wrasses, incl.
cleaner fish): are common in the Atlantic, Indian, and Pacific. They
have a protrusible mouth. Most jaw teeth with gaps between them;
teeth usually jutting outward. Size, shape and color very diversified.
Most species are sand burrowers; carnivores on benthic invertebrates;
also planktivores, and some small species remove ectoparasites of
larger fishes. Most species change color and sex with growth, from
an initial phase (IP) of both males and females, the latter able to
change sex into an often brilliantly colored terminal male phase (TP).
Males dominate several females; all Indo-Pacific species are pelagic Fig. 91a Labroides dimidiatus
spawners. Most species do well in aquaria, and young Coris are
particularly popular. Maximum length about 2.3m (Chilinus
undulatus = Napoleonfish), many are less than 15cm, the shortest
being 4.5cm.
Wrasses are carnivorous. Their diet consists primarily of parasitic
copepods and other invertebrates that are taken from the mouth and Fig. 91b Aspidontus taeniatus
gill openings of larger fish. They also feed occasionally on freeswimming crustaceans.
Blue streak wrasses are known as common cleaner fish that set up cleaning stations on various parts of
coral reefs, usually 0.5-3m. deep. They attract larger fish to their stations by making strange, oscillatory
swimming movements, and the fish then stop to get cleaned. Wrasses enter the mouth and gill openings
and remove any ectoparasites and diseased tissue. The larger fish not only refrain from devouring these
small cleaner fish, but actually readily open their mouth and gill cavities so that they are able to clean.
This is clearly a mutualistic relationship between cleaner wrasses and various larger fish of the ocean
(Grant, 1978).Many cases of interspecific mimicry, in morphology as well as behaviour, are known from
fishes. A famous example is the cleaner wrasse and its blenny mimic. While the cleaner Labroides
dimidiatus (top) is a symbiont to other marine fish, removing their ectoparasites, the mimic Aspidontus
taeniatus (below) bites off parts of other fishes' skin and fins.
Family Acanthuridae (surgeonfish): are brightly colored herbivorous
fish (sometimes also called the tang). Circumtropical, especially
around coral reefs; five species in the Atlantic, the remaining in the
Pacific and Indian oceans. All have a deep compressed body with the
eye high on the head and a long preorbital bone. Single unnotched
dorsal fin with 4-9 spines and 19-31 rays; anal fin with 2 (only Naso)
or 3 spines and 19-36 rays; pelvic fins with 1 spine and 3 (Naso and
Paracanthurus) or 5 rays. Very small ctenoid scales. A small
terminal mouth with a single row of close-set teeth. Most surgeon
Fig. 92 Acanthurus nigrofuscus
fishes graze on benthic algae and have a long
intestine; some feed mainly on zooplankton or detritus. Surgeon fishes are able to slash other fishes with
their sharp caudal spines by a rapid side sweep of the tail. They are pelagic spawners. Many species have
bright colors and are popular aquarium fishes. In some surgeon fish, such as the unicorn fish, these razor
like blades do not move, but appear as a bony curve that is quite poisonous. With the unicorn fish this
curved blade appears like a horn of a unicorn pointing forward from the nose. When these surgeonfish
are threatened by other species they will swim beside the intruder swinging their tails to inflict cuts.
When their aim is accurate the intruder will receive long, deeply slicing cuts. When humans handle
surgeonfish, extreme caution should be taken. Many unsuspecting persons has received deep wounds to
their hands when attempting to remove this fish from a net or openly handle it.
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Family Pomacentridae (Gk. poma- opercle, centron, spine), refers to
pointed margin of opercle and includes the damselfish (riffbarsch);
chiefly marine; rare in brackish water. All tropical seas, mainly IndoPacific. One nostril on each side of head; double nostrils in some
species of Chromis and Dascyllus. Body usually deep and
compressed, with a small mouth and an incomplete and interrupted
lateral line. Anal fin with usually 2 spines, very rarely 3. No palatine
teeth. About 35cm maximum length. Coloration variable with
individuals and with locality for the same species. Many species are Fig. 93a Pomacentrus coelestis
highly territorial
herbivores, omnivores, or planktivores. Damselfishes lay elliptical demersal eggs that are guarded by the
males. Included are the anemonefishes (Amphiprioninae), which live in close association with large sea
anemones. A massive presence of damselfish on the reef is a clear sign that the reef is under stress
Amphiprion (Gk. amphi-, on both sides, prion saw, refers to serrate
opercles); amongst the pomacentrids, are also found the clown- and
anemonefish; the two-band Anemonefish (Amphiprion bicinctus) is
bright orange to dark brown with two white or bluish-white bars, the
first considerably expanded across the top of the head. Maximum
recorded length is about 140mm. The anemonefish may have a
similar pattern of other clown fish, but A. bicinctus differs from
nearly all of them by having a yellowish caudal fin (it is whitish in
other species). It also differs in the expansion of the first bar over the
top of the head as opposed to the narrower bar of most other species.
A. latifasciatus, from Madagascar and the Comoro Islands is similar
to the A. bicinctus in pattern and with its yellow tail, but the midbody bar is much wider and the tail is forked. Amphiprion
chagosensis from the Chagos Archipelago and A. allardi from eastern
Fig. 93b Amphiprion percula
Africa are also similar, however they have a white tail. A. bicinctus
has been seen to be hosted by the following anemone species:
Heteractis crispa, Heteractis magnifica, Entacmaea quadricolor,
Heteractis aurora, and Stichodactyla gigantea.
Family Balistidae (L. ballista, to catapult) the triggerfish are rather
easily recognized by their flat, deep bodies, their small eyes placed
high upon the head, and by their rough, rhomboid-shaped scales,
often with small spines, which form a rough, tough covering on the
body. Near the area in front of the tail they have some prickly, spike
like, rows of spines. These spines can scratch and cause poisoning or
other fish injury. They can also cause the fish to get snagged in a net,
making it hard to remove them from it. Caution should be used
whenever handling these fish. The Orange-lined Trigger (Balistapus
undulatus) is actually the most aggressive of all the trigger species.
Fig. 94 Balistapus undulatus
Their strong jaws can reduce the hard shells of stony corals to piles of
sand.
Their striking colors can vary quite considerably. Indian ocean variants have orange tails while Pacific
ocean versions can have orange-rayed fins. They grow to a length of about 40cm.
Family Chaetodontidae (Gk. chaet-, bristle; odont, tooth) the
butterflyfish are some of the most beautiful colorful reef fish found
along with their cousins, the Angelfish (Angelfish have a spur under
each gill plate - see next page). Primarily Indo-west Pacific. Highly
compressed body. Most with bright coloration, a dark band across the
eye and an 'eyespot' dorsally. Generally near coral reefs, and
typically diurnal. Many feed on a combination of coelenterate polyps
or tentacles, small invertebrates, fish eggs, and filamentous algae
while others are specialists or planktivores. Most species occur as
heterosexual pairs. Pelagic spawners. Tholichthys larval stage with Fig. 95 Chaetodon ephipippium
the head region covered with bony plates.
The Saddleback Butterflyfish (Chaetodon ephipippium) is characterized by the large black marking on
its back which somewhat resembles a saddle. The shape of this species resembles that of some angelfish
species. The saddleback feeds on coral polyps and crustaceans.
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Family Pomacanthidae (Gk. poma, operculum; acanth, spine): are
closely related to the butterflyfish, Angelfish can be easily
distinguished from their cousins by the spur under the gill plates.
Strongly compressed body. Angle of preopercle with a strong spine.
Three spines in anal fin. Many species have an elongate extension on
hind margin of soft dorsal and anal fins. Striking coloration,
markedly different between juveniles and adults of many species. In
shallow waters of less than 20m deep, very seldom below 50m;
generally near coral reefs. All species studied to date are protogynous
hermaphrodites with 'haremic' social system. Pelagic spawners.
Fig. 96 Holacanthus tricolor
Species of Centropyge feed primarily on filamentous algae and
species of Genicanthus feed primarily on
zooplankton; most others feed on sponges, invertebrates, algae and fish eggs. Most species do well in the
aquarium, but some food specialists are difficult to maintain. The Rock Beauty Angelfish (Holacanthus
tricolor) is characterized by its black and bright yellow colors. The juvenile of the species is yellow with
a small dark spot. In the wild, this species grows to about 2 feet in length. Rock beauties are found in the
western Atlantic, where they feed on algae, sponges and coral polyps.
Family Gobiidae (Gk. gobio, fresh water): ray-finned fish, gobies,
chiefly marine and brackish, some species are catadromous (live in
fresh water and enter salt water to spawn). Often the most abundant
fish in freshwater on oceanic islands. Distribution: mostly tropical
and subtropical areas. The smallest fishes (and vertebrates) in the
world belong to this family. Mostly marine in shallow coastal waters
and around coral reefs. Most are cryptic bottom dwelling carnivores
of small benthic invertebrates; others are planktivores. Some species
have symbiotic relationships with invertebrates (e.g. shrimps) and
others are known to remove ecto-parasites from other fishes. Fig. 97 Nemateleotris magnifica
Typically nest spawners with non-spherical eggs guarded by the
male. Many are popular
aquarium fishes. The following subfamilies are recognized: Oxudercinae, Amblyopinae, Sicydiinae,
Gobionellinae and Gobiinae.
Firefishes (like this Nemateleotris magnifica) are characterized by their bright colors and by their
unusually elongated dorsal fin. This fin is used as a signaling device to communicate with other
firefishes. It is also used by the fish to wedge itself into small crevasses as a means of protection from
predators. Firefishes are found throughout the Indo-Pacific.
Family Muraenidae (L. muraena, eel): giant moray eel (riesenmuräne), it occurs on both lagoon and seaward reefs to depths of at
least 46 m. It feeds primarily on fishes and occasionally on
crustaceans. This is the largest moray eel, perhaps reaching 3 m in
length. Because of its position at the top of the reef’s food chain it is
often ciguatoxic (a skin toxin was noted in an Indo-Pacific moray
eel). Itself it is the preferred food source of the octopods. Adults
benthic, generally in shallow water among rocks and coral heads;
many species are more active at night and hide in holes and crevices
during the day.
Vicious reputation is undeserved, although some species will bite if
provoked. Feed mainly on crustaceans, cephalopods and small fishes.
Larvae (leptocephali) epipelagic, widespread and abundant. Widely
used as food, but a few large species may be ciguatoxic.
Fig. 98 Gymnothorax javanicus
Familie Congridae (garden eel, röhrenaal), ein zu den
knochenfischen (teleostei) zählende tiergruppe ist ebenso in diesen
tiefen zu finden; in grossen gruppen bilden sie bestände die im
weichem substrat sich bei gefahr blitzartig in ihre röhre zurückziehen.
Fig. 99 Heterocephalus sp
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Fish in the Reef Ecosystem77:
Impact of fishes in reef ecosystem is highly varied, with fish playing many roles on the reef stage. Moreover,
the scene is constantly changing on the reef stage, so that the cast of characters is in constant change. We see
this change most readily on a day to night basis, which is termed the diel cycle.
Reef by day: a scene crowded with diverse fish activity, with day active fish highly specialized in feeding
behavior.
A. Bottom feeders (benthic feeders):
• Pomacentridae: damselfish, sergeant-majors; anemonefish
• Gobiidae: cleaner gobies;
• Chaetodontidae: butterflyfish;
• prey on shelly benthos Labridae: hogfish, wrasses;
Balistidae: triggerfish;
Tetradontidae: pufferfish;
• feed on sponges Pomacanthidae: angelfish;
Zanclidae: moorish idol;
• grazers Scaridae: parrotfish;
Acanthuridae: surgeonfish;
• sand bottom feeders Ostraciidae: trunkfish:,
Botidae: flounder;
Suatinidae: rays;
• ambush predators: Batrachoididae: frogfish, toadfish;
B. Waters above the reef (pelagic feeders):
• Plankton feeders: Labridae: creole wrasse,
Pomacentridae: chromis;
Balistidae: durgon;
Lutjanidae: snappers;
• Stalking predators: Aulostomidae: trumpetfish;
Belonidae: needlefish;
Sphyraenidae: barracuda;
• Other predators: Muraenidae: moray eels;
Serranidae: groupers;
Carangidae: jacks;
Carcharinidae: sharks;
• Some schooling fish like Haemulidae: grunts are inactive by day but feed elsewhere at night
Reef at twilight.
A. About 1hr before sunset, night active fish take cover.
1. There follows a quiet period of ~20 min when midwater stage is relatively empty.
2. This is the time when predators have an advantage.
B. About 30min after sunset, fishes like squirrelfish and bigeyes stream out of caves to feed in midwaters.
Near reef, fish are protected from fast-moving predators, but move out at night.
Reef by night.
A. Fish like bigeyes move offshore to feed.
B. Other predators, like puffers, morays, feed closer to reef.
C. Level of fish activity is much reduced.
D. Many "actors" from daytime "soap-operas" rest by night, sometimes relatively exposed, or protected in a
mucus-sheath sleeping bag (as do parrotfish, Scaridae).
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Class Reptilia (L. reptare, to crawl)78: the majority of marine reptiles are sea turtles; however, there are some
sea snakes and some marine lizards (like those found on the Galapagos Islands). Sea turtles fall under the
category of marine terapods which are marine organisms with four legs. Crocodiles and alligators also fall
under this category. Most marine turtles are endangered or threatened and so it is important to take measures to
keep their numbers from declining further.
Many millions of years ago, long after the great reptiles had colonized the land, some of them decided to return
to the sea. Today, reptiles are not the most common residents of the reef, but they are definitely among the most
beautiful. Perhaps the most well known reptiles in the sea are the turtles. There are many different species of sea
turtle, ranging in size from only 60cm to the real giants at over 150cm in length. Sea turtles lay their eggs on
land. They can be seen on the beaches late at night digging a deep hole in the sand. The eggs are deposited and
covered over. Several months later, the tiny turtles dig their way to the surface and scramble towards the sea.
But a turtle's life is not easy, Only one in a thousand will survive the predators and return to the beach one day.
Sea turtles were once killed by the thousands for food. Today, even though many face extinction they continue
to be exploited. Their eggs and shells are in constant demand the world over.
Another member of the sea reptile family enjoys full protection. The sea snake is the most venomous snake on
earth. Several sea snake species can be found swimming the worlds reefs. Some of them are spectacularly
colored. Divers are weary of this animal, but the sea snake is timid and will not attach unless provoked. Below
is a list of some of the more common reptiles found on the reef.
Subclass Testudinata (L. testudo, tortoise) anapsid reptiles encased in a
plastron and carapace; order Chelonia (Gk. chelone, turtle);
Family Cheloniidae (Hawksbill Turtle) gets its name from its hawklike beak. It ranges in size from 1m to 1.3m in length. This turtle's
shell is the source of "tortoise shell", and because of this commercial
exploitation has caused their numbers to dwindle. Their shell and oils
are in constant demand, placing this turtle in danger. The hawksbill
sea turtle as many other sea turtles is omnivorous, feeding both on
plant and animal material. It prefers grasses and other plants from the
bottom of the ocean as well as from grass beds that float at different Fig. 100 Eretmochelys imbricata
depths. It also consumes small animals and sometimes the dead
remains of marine creatures.
Subclass Diapsida (Gk. di, two; apsis, bar) reptiles with a diapsid or
modified diapsid skull; order Squamata (l. squama, scale);
Family Elapidae (sea snake) it can be found inhabiting most reefs of
the world. Sea Snakes differ from terrestrial snakes in that their tails
are flattened to form a paddle. This helps to propel them through the
water. Even though the sea snake is the most poisonous snake in the
world, they are not aggressive and rarely bite humans. This snake is a
carnivore. It forages during the day, hunting by ambushing its prey. It
is venomous snake, and it chews poison into fish and then swallows
them.
Fig. 101 Pelamis platurus
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Class Mammalia79 (L. mamme, breast) all mammals share three characteristics not found in other animals: 3
middle ear bones , hair; and the production of milk by modified sweat glands called mammary glands
(mammals feed their newborn young with milk, a substance rich in fats and protein). Several million years ago,
the first animals moved from the sea to colonize the land. Eventually, world-wide changes in climate and
geography convinced some of the mammals to move back to the sea. These animals have since evolved to be
perfectly adapted to their environment. Most of these animals comprise a group known as the cetaceans, which
includes the dolphins and whales. The other main group of marine mammals fall into the pinnipedia family,
which includes the seals and sea lions. Breathing air and then diving, cetaceans can hold their breath for
unimaginable lengths of time. They are peaceful animals, and they are quite intelligent. These animals have
exhibited remarkable abilities to communicate and learn. Their natural lives are spent in close family groups
caring for their young and each other. Their songs can be heard echoing for miles beneath the waves. Below is a
listing of some of the world's more familiar marine mammals.
Order Celacea (L. cetus, whale) large massive mammals; pectoral limbs
reduced to flippers, pelvic limbs lost, large tail bears horizontal flukes
which are used in propusion.
Family Balaenopteridae (humpback whale, buckelwal) the
cerebellum of the humpback whale constitutes about 20% of the total
weight of the brain; the brain does not differ much from those of
other mysticete whales. The olfactory organs of humpback whales are
greatly reduced and it is doubtful whether they have a sense of smell
at all. Their eyes are small and adapted to withstand water pressure.
Their external auditory passages are narrow, leading to a minute hole
Fig. 102 Megaptera
on the head not far behind the eye. Humpback females are larger than
novaeangliae
the males. They are one of the few species of mammals for which this
is true. The most distinctive external features of humpbacks are the flipper size and form, fluke
coloration and shape, and dorsal fin shape. Flippers are quite long and can be almost a third of the body
length. They are largely white and have knobs on the leading edge. The butterfly-shaped tail flukes bear
individually distinctive patterns of gray and white, and have a scalloped trailing edge. The dorsal fin can
be a small triangle or sharply falcate, and it often has a stepped or humped shape; this is one source of
the name "humpback." They are animals are quite large, growing to 18m in length. They feed on
plankton, and are perhaps best known for their enchanting songs which can be heard for hundreds of km
under the sea.
Family Delphinidae with 32 species placed in 17 genera, this is by
far the largest family of cetaceans. Delphinids are small to mediumsized cetaceans, ranging from about 1.5m in length and 50kg weight
to almost 10m in length and 7000kg. Males are usually larger than
females. The shape of the head of many delphinids is distinctive; the
forehead appears to bulge over the beak-like rostrum due to the
presence of a lens-shaped fatty deposit called a "melon". This
structure may help focus the sound emitted by these animals in
echolocation and feeding. Other delphinids possess a melon, but their
rostrum is short and the bulging forehead merely gives the head a
Fig. 103 Tursiops melaena
squared-off appearance. The bodies of most species are sleek and
streamlined. Most have dorsal fins, which are usually curved (falcate), but much variation exists. The
group includes bottlenose dolphins, killer whales, pilot whales, Pacific striped dolphins, and many more.
The Bottlenosed Dolphin (Tursiops melaena) is perhaps the most familiar of the sea mammals. Their
gentle nature has endeared them in our hearts.
Order Sirenia (Gk. a sea nymph that lured marines to their death)
includes manatees and dugongs. Are marine herbivores with their
long tail is horizontally flattened.
Family Trichechidae (manatees) they are somewhat seal-shaped
with forelimbs (flippers) adapted for a completely aquatic life and no
hind limbs. Lungs extend the length of the animal's body, which is
important in controlling position in the water column. Hair is
distributed sparsely over the body and the surface layer of skin is
continually sloughing off (believed to reduce the build-up of algae on
their skin). The Manatee is a graceful and peaceful creature. They
Fig. 104 Trichechus manatus
feed on water plants, and inhabit the waterways and shores of Florida
are found in the Indian ocean and the Gulf of Mexico. They are slow creatures, and are in danger of
extinction due to careless boaters.
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Part VI - Reef Responses to Environmental Parameters80 – Construction versus Destruction:
The first pages mostly dealt with the biodiversity of reef organisms and their construction over time. On page 5
of this document (constructive components of reef) some key elements are listed that contribute to the
establishment of a reef structure; i.e. (1) foundation, (2) framework components, (3) encrusting
Components, (4) bafflers and binders.
Coral reefs are constantly built and degraded by biotic elements (bioerosion). Bioerosion as such is not an
entirely bad thing as it provides new substrate and raw material in order to allow rejuvenation of the reef
structure. Synergistic effects that come from outside (greenhouse warming, pollution etc.) increase the overall
stress balance which ultimately leads to the overall degradation of a reef (so called give up refs - see following
section: “a balance between CONSTRUCTION vs. DESTRUCTION”).
Parameters favoring the “build-up” of reefs (constructon):
In order to make sure that reefs proliferate at all; some major limiting factors on coral reef establishment have to
be addressed first, growth and persistence of coral reefs are connected to:
A. Temperature
•
B. Salinity
•
•
•
C. Light
•
•
•
D. Water motion
•
•
•
E. Sedimentation
•
•
•
•
Restricted to waters warmer than 18oC, usually 26-28oC, and less than 36oC;
corals are stenothermic organisms; at temperatures between 30-32°C, corals
stop growth and reproductive activity to save energy (prolonged elevated
temperatures cause bleaching = exocytosis of zooxanthellae, corals turn white).
Therefore, geographical limitation in-between 25o N and 25o S latitude.
Reefs require "normal" salinity ~35%o (parts/1000 = 35gNaCl per liter of
water); heavy rainfall, river runoff can be lethal as salinity levels sink below this
threshold level (mixohalinic zones).
Some reefs are adapted to higher salinity (40%o in euhalinic reefs) due to
persistent evaporation and reduced water circulation.
Reefs require sunlight for vigorous growth (photosynthetic zooxanthellae alge).
Because light penetration decreases with water depth, reefs are restricted to
shallow water, generally above 100m.
Some corals modify colony form in response to light, e.g. massive corals such
as the Caribbean Montastrea annularis grow as rounded heads in shallow water,
but forms flat plates in deeper water in order to improve light capture.
Reefs require constant water circulation and currents in order to obtain
suspended food, oxygen, as well as the removal of sediments.
Some corals resist strong wave energy.
Some corals modify colony form in response to strength and pattern of water
motion, e.g. Acropora palmata, the elkhorn coral of the West Indies, will grow
as parallel-aligned branches, pointing in the direction of wave oscillation in
areas where there is strong wave motion, but will form 3-dimensional colonies
where wave action is reduced.
Heavy sedimentation can smother reefs.
High turbidity (suspended sediment) reduces light penetration.
Reef growth is reduced or absent along coastlines with high input of sediment
from river runoff (e.g. Amazone river delta - BRA).
Corals have varying ability to shed sediment (see: D'Elia, Buddemeier, and
Smith81).
Fig. 105 All dead surfaces of the reef are rapidly
overgrown by a thin film of filamentous green
algae. These form broad algal turfs that are a
favorite diet of many fishes and urchins.
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Reef Degradation 82
Now we focus our attention to the degenerative forces acting upon a reef which ultimately may lead to the
destruction of an entire reef section.
Destruction of reefs - ABIOTIC factors:
Chemical environment, the following chemical criteria modify the biocoenosis of a reef community:
A. Carbonate mineral saturation: can affect coral calcification, skeletal chemistry/mineralogy;
1. dissolved CO2 in sea water will equilibrate the increased partial pressure of CO2 in the atmosphere,
reducing carbonic supersaturation in tropical waters; increased CO2 results in larger H2CO3,
ultimately slowing CaCO3 precipitation;
B. Salinity: corals are stenohaline (support only small fluctuations in salinity levels);
1. changes in rainfall, runoff alter salinities, often affecting reef growth;
2. elevated salinity from evaporation occurs on a local scale;
C. Nutrients: anthropogenic sources (chemical pollution in general) may trigger bacterially mediated
diseases like black band disease (BBD) or cyanobacterial blooms (red tides); sources include fertilizer
runoff, soil erosion, waste disposal have chronic local and regional effects;
1. phosphate affects coral skeletal growth;
2. nitrate promotes algal growth, tipping competitive balance away
from corals;
eutrophication causes the zooxanthellae to feed on N-sources of the
eutrophicated water rather than on the N-metabolites of the coral
host; this increases the competition between zooxanthellae and coral
animals for H2CO3 and CO2, thus halting CaCO3 precipitation;
D. Oxygen levels: should be kept at optimum levels to avoid damages Fig. 105a Eutrophication on the
reef triggering algal blooms
to the sessile fauna;
4-8mL/L at the water surface due to photosynthetic activity and
mixing with atmospheric layer; O2- consumption in flat lagoons deprived of zirkulation (at night
and with low tide - as low as 1-2mL/L).
E. Toxic/artifical compounds: anthropogenic sources; xenobiotica may act as growth inhibitors,
mutagens, or sex modifiers; increased pollution has also contributed to mor commonly observable
harmful algal blooms (HABs):
Often, these events are accompanied by severe impacts to
coastal resources, local economies, and public health (Raven, et
al. 1992). In general, most harmful algal blooms are caused by
plants (photosynthetic organisms) that form the "base" of the
food chain. It is a challenge to define a harmful algal bloom and
to characterize the species that causes it. Examples of HABs
that are readily associated with water discoloration are blooms
of many species of cyanobacteria, generally visible as floating
green scums or colonies in coastal environments; two "brown
tide" species (Aureococcus and Aureoumbra) that turn coastal
lagoons dark chocolate brown; the dinoflagellates Alexandrium
spp., Gymnodinium breve, and Noctiluca spp., that cause red
water (red tides). However, no color is visible in other harmful
species, such as the chlorophyll-free dinoflagellate Pfiesteria
piscicida, several Dinophysis species, and benthic microalgae
(e.g., Gambierdiscus) that grow on the surfaces of larger
macroalgae in tropical waters (Burkholder and Glasgow 1997,
Smayda 1997). In comparison, macroalgae are considered
harmful due to dense overgrowth that can occur in localized
areas, such as coral reefs of the tropics or coastal embayments Fig. 105b A "red tide" bloom of
receiving excessive nutrient loading (LaPointe 1997, Valiella et Noctiluca colors the seawater.
al. 1997). Accumulations can be so high as to cover the bottom
Noctiluca is the largest of the
of a region, excluding other biota as well as creating an dinoflagellates measuring about
environment in which high oxygen consumption and the
2mm in diameter.
associated anoxic conditions accompany decomposition of the
accumulated or displaced biomass.
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Physical environment, the following physical criteria modify the biocoenosis of a reef community: naturally,
such destruction is related to the interaction of energy possessed by waves, tides and currents with the framework of a reef system. Note that as one examines the distribution of energy across the reef (from deep forereef
to shallow reef crest) the energy of wave systems progressively increases. Thus, the impact of waves across this
section results in increased breakage and abrasion of the structures developed by corals and other reef
organisms.
A. Sea level rise: global eustatic rise predicted to be 8-29cm by 2030 and 50-150cm by 2100. Therefore
rise in sea level is not of immediate concern as it has occurred in the past. Effects of sea level rise:
1. increased reef growth on reef flats, along coasts where current sealevels now act limiting;
2. deeper reefs unable to keep up;
3. changed patterns of coastal erosion, affecting intertidal ecosystems;
4. increased circulation and sedimentation in once restricted environments;
5. altered recruitment and composition of benthos;
6. modified shallow water habitats.
B. Temperature: a key variable, which is related to global climate change (remember, corals are
stenothermic organisms). Effects include:
1. unusual elevations can lead to bleaching, and subsequent death. Greenhouse effect may cause a rise
of 2°C in the tropics for a doubling of CO2; even a fraction of this in sea surface temperature could
be damaging to reefs. Other causes are El Nino (e.g. of late 1996/97 in Seychells and Maledives) or
local anthropogenic effects;
2. synergism with light exposure documented and interactions with other parameters are likely;
3. lagoonal areas or other flat-water reef communities may experience increased temperatures during
low tides when water circulation is shut off (atolls with a closed coral coverage).
C. Oceanic currents: wind-driven patterns determined by global climate regime;
1. control nutrient levels, temperatures, by upwelling, water mass advection.
2. transport reef propagules (vegetative reproductive fragments), affecting reef distribution.
Storms and wave energy: increased wave action due to typhoons (= cyclones = hurricanes), quakes,
and tsunamis:
1. provide a natural catastrophic pruning and/or substrate renewal;
2. influence succession and diversity;
3. wave energy reflects winds to affect reef growth.
D. Visible light required for photosynthesis in zooxanthella: light reduction can result from increased
cloud cover, turbidity, or atmospheric pollution;
1. increased turbidity in the water column attenuates light to an extent that photosynthesis and
calcification are reduced within a few meters to tens of meters;
2. reduced light penetration can significantly reduce optimum depth zones for reef growth.
Ultraviolet light: destruction of stratospheric ozone layer is expected to increase surface UV exposure.
1. imposes physiological stress on shallow-water organisms;
2. may be mutagenic.
3.
E. Mechanical damage: antrophogenic influences acting directly onto
reef organisms;
1. achor damage, and damage caused by direct impaction
(kollision with boats, tankers, freighters, etc.);
2. damages caused by the recreational industry (diving,
snorkelling, etc. reef walking, sitting on coral heads), military or
other commercial activity leads to chronic damages, irritations
and ultimately results death of coral colonies.
Fig. 106 Repair after a tanker
crashed against a reef (top)
F. Sedimentation: from rivers, building activity, fly-ash, coastal water
run-off, etc.;
1. can reduce coral growth rates or totally smother corals;
coverage of hard substrate by soft sediment can limit coral
recruitment;
2. rise in sea level will cause increased erosion, sediment outfall
onto reef areas;
3. many anthropogenic sources of sediment influx: dredging,
deforestation (soil runoff), agriculture (eutrophication), Fig. 106b turbidity due to suspended
construction (extra sedimentation).
sediments
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Destruction of reefs - BIOTIC factors: inter- and intraspecific wars (see Kleemann VL …. /bioeros.pdf)82
The construction of the reef system is continuously counterbalanced by biodestructive processes. The reef is a
community of organisms, all of which interact in a complex trophic (or feeding) structure. Some organisms can
be major destructors of the reef simply as a result of their efforts to obtain food. For example, in addition to
living tissues of the corals, algae and organic debris litter the reef surface which other animals actively use as
foodstuff for their existence. Thus, a great variety of reef organisms act to destroy reef framework by biting,
boring, excavating, rasping, etching, or scraping at the substratum. The process of destruction of hard reef
substratum by organisms is called bioerosion. As bioerosion weakens the reef framework to a point at which it
may collapse due to its own weight or as a result of storm activity (Goreau & Hartman, 1963), it occurs for
mainly two reasons.
1. Protection: from intense predation pressure on reefs. As a result, much reef biomass and diversity is
cryptic. Many borers of this type are permanently encased in their borings.
2. Feeding: biters, raspers, scrapers remove hard substratum in process of ingesting soft tissue of algae,
coral. Borers and drillers penetrate shells to obtain goodies within.
Accordingly, biodestructive organisms can be broadly grouped into:
Munchers and Crunchers: some animals, particularly the parrot fish and some starfish actively prey upon
the living coral polyps. For example, it is common to hear the crunching of the strong parrot fish beaks
as they clip the growing tips off of living coral branches. Similarly, the crown of thorns (A.planci
starfish) everts its stomach around a branch of coral, secreting digestive fluids until the coral tissue is
dissolved, and then absorbing this "coral broth" directly through its stomach tissues. In the normal reef
setting, the growth rate of corals greatly exceeds the rate at which these organisms can destroy the reef.
However, when the ecologic balances are upset and populations of these organisms increase beyond
normal limits, their destructive actions can lead to the devastation of broad areas of the reef surface.
Grazers: given the vast amount of algae that infest most surfaces of the reef, it is not surprising to have
animals graze upon these fields of photosynthetic foodstuffs as part of their ecology. Perhaps most
significant of these animals are the sea urchins, sea cucumbers, etc. (Echinodermata). In particular, the
sea urchin possess a series of five teeth that serve as small scrapers and scourers that can actively break
up the surface of the coral reef skeleton. It is common to find the stomach contents of these urchins to be
filled with fragment of the coral skeleton. As a result, such feeding can be quite destructive to the reef.
Borers: this is a unique life style whereby organism actively drill or etch into the dense skeletons of the
coral reef. One example of such animals is the boring clam, Lithophaga which means "rock eater". If one
were to cut a trench across the reef.....the dead and discarded skeletons of the reef corals are commonly
riddled by numerous channels and tubes which were formed by these clams boring through the skeleton
in search for food. Overall, this does not actively destroy the living reef structure and therefore is more
of a passive process.
Methods of bioerosion.
A. Chemical erosion is restricted to carbonates and mediated by proton activity (H+):
1. Drilling gastropods use chemical softening followed by rasping.
2. Clionid sponges dissolve out chips which are released to sediment (≈30% of lagoonal sediments).
3. Endolithic algae (BGA, GA, RA), fungi (occur deeper)
B. Mechanical erosion is not restricted to CaCO3-substrata:
1. Scraping, rasping by means of radula (chitons, gastropods), jaws (echinoids).
2. Biting by parrotfish with strong jaws, predation on shells by crabs, birds, fish.
3. Boring by bivalves (Lithophaga, Gastrochaena, Tridacna), polychaetes, sipunculids, shrimp
(Upogebia, Alpheus), barnacles (Lithotrya)
Fig. 107 bioerosive activity excerted by sea
urchins on a Porites colony (left), endolithic
activity due to microorganisms
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Competition: interaction for resources in short supply (food, space) between
two species in which both are harmed or inhibited as a result of the
interaction.
A. Interphyletic (competition between phyla), interspecific (between
different species) and or intraspecific competition (between same
species): because of the intense competition for space on the reef,
many corals have adopted methods by which to "stake a claim," and
allow room for growth and expansion. These specialized tentacles are
very adept at this purpose. Not only do the Euphyllia species form
sweeper tentacles but Galaxea is known for its mere long thin
threads.
Aggression in corals (Lang, 1971, 1973).
• Extra-coelenteric digestion of corals sitting next to each other.
Done by extrusion of mesenterial filaments through polyp wall.
• A pecking order was established for Jamaican reef corals:
1. Solitary corals outcompete massive colonial species and fast
growing branching species.
2. Aggressive ability allows slower growing species to maintain
living space.
B. Competitive networks (Jackson, Buss, Hughes):
• Cryptic faunas of reefs: bryozoans, sponges, tunicates.
• Long term studies of overgrowth and other competitive
interactions between cryptic spp. done using artificial substrates.
• Results showed not just linear hierarchies in competitive abilities
but return loops and networks in which some inferior competitors
may outcompete some spp. ranking above them.
Effects of competition can be revealed when a grazer such as Diadema is
removed (termed ecological release):
Prior to 1983-84, Diadema antillarum was a major reef herbivore,
grazing on algae, sometimes consuming live coral, in the Caribbean.
Mass mortality, (disease ?) eliminated close to 100% of Diadema
throughout Caribbean in 1983/84. Removal of this efficient grazer
resulted in increased algal growth, boosting competition against
corals. In absence of a controlling factor, competition can become a
major force in shaping reef community.
Fig. 107a Coral warfare against
intruders
Fig. 107b Sweeper tentacles in
Euphyllia sp
Predation: predators of corals are more numerous than has been realized.
A. Fish (development of septal spines in corals may deter predators):
• Parrotfish (Scaridae) rasp live coral to 2-3 mm depth to feed on
zooxanthellae, or bite off tips of branching corals exposing bare
skeleton to bioerosion, so do triggers (Balistidae), filefish (Mona- Fig. 107c The colonial sea squirt
canthidae), puffers (Tetraodontidae), and some wrasse (Labridae).
Aplidium sp. is overgrowing a
• Other fish predators include damselfish (Pomacentridae) which sea cucumber (prob. Eupentacta
cultivate algal gardens (1/4-1/2m2 per fish, entire colonies of
sp.).
damselfish can occupy a huge area on the reef), while the damsel
Microspathodon chrysurus feeds on coral polyps, leaving "kiss-marks" on coral, surgeonfish
(Acanthuroidae), butterflyfish (Chaetodontidae).
B. Molluscs:
1. Gastropods, Jenneria pustulata, Coralliophila abbreviata, C.
violacea (has no radula, but suck polyps from skeleton), Cyphoma
gibbosum (feeds on gorgonians), Magilus antiquus (let itself
overgrow by the coral), Quoyula madreporarum (sessile snail that
feed on coral tissue), Epitonium lura, E.replicata (have radula but
suck polyps out of skeleton), Prinovula sp., Cyphoma gibbosum
(gorgonian feeding snail), Drupella cornus (corallivorous).
2. Bivalves: Gastrochaena and Lithophaga etch their way into the
Fig. 108 The sponge Stylissa
coral, with only their siphons emerging at the top (“keyholes”);
stipitata, being eating by the
Tridacna crocea erodes reef substrate to form a grove where it nudibranch Discodoris heathi.
can settle into, exposing just the fleshy mantle to the waters.
3. Nudibranchs: aeolids consume coral polyps and incorporate nematocysts and zooxanthellae.
C. Fireworms: in Caribbean, Hermodice carunculata prefers branching Porites but will also take Acropora
or Millepora. Damaged tips of Porites can be repaired by overgrowth, forming club-shaped branches.
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D. Crustaceans (mostly crabs):
Mithrax sculptus in Caribbean; pagurids (hermits).
E. Echinoderms:
• Echinoids: sea urchins (E.lucunta, D.antillarum of the Caribbean,
E.matei, D.setosum of the Indo-Pacific) can be a coral predator
and source of bioerosion.
• Asteroids: all Pacific (Acanthaster planci, Culcita coriacea,
Choriaster granulatus, Pharia pyramidatus).
F. Endolithic organisms:
Fig. 109a The red sponge at the
• Thallophyta are endolithic marine algae that etch their way into
bottom is overgrowing and
the carbonate skeleton; e.g. Ostreobium species gernerate the
killing the grayish coral
greenish band within the euphotic range shortly under the
(Caribbean)
coenosarc.
• Porifera (Cliona sp.) are able to dissolve entire colonies within a
short time and generate an enormous amount of fine carbonate
sediments.
G. Epilithic organisms:
• Cyanobacterial species like Oscillatoria, Schizotrix, Microcolus,
etc. actively try to settle on healthy coral tissue, triggering coral
diseases due to a toxic shock (e.g. white band disease).
• Algae: the red alga Metapeyssonnelia corallepida, as well as the
brown alga Lobophora variegata overgrow mainly Millepora Fig. 109b An ascidian (arrow) is
complanata and M. alcicornis, but also other corals with smooth overgrowing a branching coral.
surface, such as Porites porites and P.astreoides. In general,
nutrient enrichment that causes eutrophication favors algal
overgrowth of coral reefs.
• Encrusting Porifera are known for their out-competing capability
to overgrow coral colonies; Tepius sp ? even possesses
endosymbiotic cyanobacteria (resulting in a toxic shock and is
considered to trigger WBD in corals which ultimately can
“mutate” to BBD); Chondrilla nucula is considered to be an
epizoic spongy disease overgrowing coral heads.
Fig. 109c Chondrilla nucula
• Ascidiaceae: some ascidians grow upward by engulfing branching
corals.
Anti-predation defenses among reef organisms.
A. Diverse and well-developed.
B. Toxins for self-defense:
• 73% of species of sponges, tunicates, echinoderms from the western Pacific were found to be toxic to
fishes.
• Soft corals secrete toxins and show a hierarchy of toxicity.
C. Morphologic defenses mechanisms:
• Spinosity and shell strengthening in mollusks; more extensive in west Pacific than in Caribbean.
• Spinosity, regeneration in comatulid crinoids.
D. Nocturnal habits to escape daytime predators:
• Comatulid crinoids, basketstars.
• Nocturnal predators: octopus, morays, other fish.
Chemical communication for the "peaceable" exchange of
information as well as for chemical aggression and defense is by no
means restricted to the terrestrial world: pheromones and
allelochemicals are well known from fish, marine invertebrates, and
algae. The coexistence of immobile organisms such as corals or
sponges in complex communi-ties is to a large extent chemically
mediated, their defense systems being made up of highly active
allelochemicals. Some of these compounds exhibit exciting
physiological properties which are of high medical and agrochemical Fig. 110 Clownfish and anemone
interest. Mechanisms of adaptation, include tolerance and symbiosis,
relationship
feeding preferences, and chemical mimicry are all among the basic
aspects of coevolution which are currently subjects of detailed study.
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Coral Diseases83:
apart from the biotic and abiotic factors mentioned above (light, temperature, salinity, sedimentation/turbidity,
substrate availability, nutrient levels, bioerosion, etc.) some other factors determine the successful establishment
of reef communities: disease, and physical damage caused by anchor damage, SCUBA diving, dredging, etc.
(Hallock et al. 1993, De Freese 1991, Jaap 1984, Glynn 1986, Lapointe 1997, Bell 1990).
In order to understand the growing appearance of coral diseases and to stabilize at least the current status quo,
coral pathology has to step out of its neglected existence to become a growing side-branch of coral reef science.
Reefs are very sensitive to environmental conditions. They are adapted to extreme oligotrophic conditions.
Under normal conditions, diseased or even dead corals never exceeds 5% of the total undisturbed reefs. But
changes in coral health and vitality (disease, algal overgrowth, bleaching, etc.) may be more sensitive indicators
of changing environmental conditions. All the man-made stresses (chemical and thermal pollution,
sedimentation, dredging, blasting, boat anchoring, recreational activities, etc.) not only exert considerable
pressure on these organisms, but also enforce the frequencies of coral pathogens. Thus, pathologic syndromes of
reef corals are commonly grouped into those acting without and those mediated by a pathogen.
Disease working without a pathogen: although no pathogen is involved in the progress of the disease, the
pathogenic reaction is caused by external influences as in the cases of Tissue Bleaching (TBL), Shut-DownReaction (SDR), and White Band Disease (WBD).
Tissue Bleaching (TBL): coral bleaching or tissue bleaching refers to the
whitening of coral colonies brought about by a reduction in the
number of zooxanthellae from the tissues of polyps, by a loss of
photosynthetic pigment (exocytosis of zooxanthellae). Corals
naturally loose less than 0.1% of their zooxanthellae during processes
of regulation and replacement. However, adverse changes in a coral's
environment can cause an increase in the number of zooxanthellae
lost. This loss exposes the white calcium carbonate skeletons of the
coral colony while the coenosarc is still present (a gentle touch
reveals the presence of the living tissue - slippery feeling reveals the
presence of coenosarc, a rough and sharp indicates a dead colony);
depending upon the duration of the bleaching event, some
zooxanthellae may stay in the dermal tissue of the coral host and may
Fig. 112 Montipora annularis
reproduce after the event is over. Under favorable conditions, corals
(above) and Diplora
may suvive even for an entire year without the algal symbiont. There
labyrinthiformis (below).
are a number of stresses or environmental changes that may cause
Picture taken in Oct.1987 (left)
bleaching including excess shade, increased levels of ultraviolet
and after recovery in Aug.1990
radiation, sedimentation (necrosis in soft corals), pollution, salinity
(right) - Key Largo FL
changes, elevated atmospheric CO2 levels, industrial seawater
pollution, excess freshwater runoffs, and increased surface water
temperatures linked to the phenomenon known as ENSO (El-Nino – Southern Oscillation) events67,
which causes TBL in the upper water layers (0-<15m) among coral (TBL in deeper water, without
perceptible temperature changes, remain largely unexplained). Temperatures that stay around 33°C
(sublethal level) block resettlement of zooxanthellae into the host; corals may survive for another few
months. Temperatures above 34°C cause the immediate death of the coral colony, even though symbiotic
algae may still reside within the dermal tissue of the organism. Sattellite telemetry allows to monitor seasurface temperatures and makes it possible to track hot-spots and follow them as they migrate across the
oceans (usually coupled with eddies that measure more than 100km in diameter).
Shut-Down-Reaction (SDR) - often referred to as Rapid Wasting (RW),
Rapid- or Stress-Related Tissue Necrosis (RTN/SrTN), White Plague
(WP), or White Death (WD). Observations in laboratory experiment
and field observations ofcorals under sublethal (abiotic) stress such as
elevated temperature, sedimentation, chemical pollution, have
revealed that specimens can die from a simple scratch. Such sudden
disintegration of the coral tissue, which starts at the margins of the
injury, is characterized by sloughing off the tissue in thick strands of
blobs from the coenosarc, leaving behind a completely denuded coral Fig. 122 Montastraea annularis
looks like parrotfish bits?
skeleton. From the initial interface, the phenomenon proceeds in an
enlarging circle on massive corals, or moves along the branches in ramose forms, spreading to all sidebranches upon reaching a junction. It is still unclear if SDR represents a disease on its own, as the
thriggers match those in WBD or WS (see below), although there seem to be significant differences
regarding the speed this disease affects a colony.
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Thus, SDR is especially dangerous as it can spread with an average speed of 10cm/hour – fast enough to
be visually observed! Being contagious, SDR can be transmitted by a floating strand of dissolved,
contaminated tissue to produce an onset on a neighboring stressed colony. Thus, triggering a catastrophic
chain reaction, whichmay occur several times during the course of a season. It usually affects species of
the Caribbean, such as small star corals Dichocoenia stokesii, pillar corals Dendrogyra cylindrus, and
boulder corals Montastrea annularis.
White Band Disease (WBD): as the name suggests, it refers to a band of
white coral skeleton that represents a moving front of tissue
destruction of scleractinian corals. Although less aggressive than
SDR - it is not infectious and contagious, but advances with an
average speed of a few mm/day. Several attempts at finding a distinct
pathogen have been unsuccessful, although smears of WBD regularly
yield a considerable variety of bacteria (GramPOS, GramNEG, and
cyanophyta). WBD is strongly affected by abiotic conditions (e.g.
temperature), and can be triggered by the settlement of blue-green
Fig. 113 Acropora palmata
algae which are toxic to corals.
The site of settlement of blue-green algae is usually outlined at the interface of the coral corpus with the
benthic sediment (shaded area, at the base of the coral). Settlement can also occur on damaged surfaces
caused by external influences (wave action or damages caused by snorkelers or divers). An algal turf of
green color, e.g. Chlorophyta, is considered harmless, whereas a dark pigmented algal overgrowth of
Cyanophyta may trigger WDB. Reef structures affected by WBD can lead to a massive die-off, favoring
tumors and is always accompanied by parasitic microorganisms (GramNEG rod-shaped bacteria, ciliates,
protozoans, acoel turbellarians, nematodes, tiny copepods and amphipods) which result in algal
overgrowth and subsequent death of the coral which are then successively colonized by invertebrates,
gastropods, and boring clionid sponges (weaken the coral skeletons) and make them more susceptible to
breakage during storms. Recent studies tend to further differentiate WBD into the classical form as type I
and a somewhat altered form WBD-II;
WBD-I: GramNEG rod-shaped bacteria were found in the tissues of affected corals. However, as
mentioned above, the role of this microorganism in the development of disease has not been determined.
WBD-II: in this disease, a margin of bleached tissue appears before the tissue is lost. Bacteria of the
genus Vibrio have been found in the surface mucus of the bleached margin.
Diseases with pathogens: these involve the presence of a distinct disease causing agents; this group includes
Bacterial Infections (BI) Fungal Infections (FI) and other epozoic organisms resulting in death of the coral
colony.
Bacterial Infections (BI). Mucus production is the main defense mechanism
against outside intruders and is important to fight diseases. But
sometimes the mucal slime consisting mainly of glycopeptides, can
lead to an unwanted cultivation of carbon and nitrogen feeding
microorganisms, dominated by Desulvovibrio and Beggiatoa species
in its final stages. In sever cases, when attacked by Phormidium
corallyticum it is almost certainly will infect the coral tissue with
Black Band Disease (BBD - see below). Heavy microbial activity
Fig. 114. it begins with the
along with trapped sediments, quickly lowers the dissolved oxygen
protective mucus layer as shown
level of the closely surrounding waters, suffocating the delicate coral
on this Siderastrea sidera
tissue underneath. Only strong wave action or currents can save the
coral by mechanically ripping off the slimy coverage within days after formation.
Black Band Disease (BBD): BBD is probably the best-known
pathogenically caused coral disease. Similarly as in WBD a black
band of "grazing" bacterium called Phormidium corallyticum (=
Oscillatoria submembranacea a photosynthesizing, gliding,
filamentous cyanobacterium) appears in association with other
bacteria; e.g. cyanobacterium Spirulina sp. and proceed progressively
outward, thus affecting the entire colony. Being contagious, BBD can
spread easily to other corals by means of wave action. P.corallyticum
Fig. 114a Diplora sp
eats its way from the upper surface where it spreads relatively fast, to
the edges of the coral surface. Under certain circumstances
microscopic densely interwoven algal filaments (trichomes without significant cell wall constructions) of
the pathogen form a blackish mat (predominantly on scleractinians of the family Faviidae).
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If enough light is available, to form a tiny algal spot, it gradually turns into a dark ring of tissue-stripped
coral skeleton that proceed onwards with a few cm/week, enlarging the denuded area. Small corals can
be deprived entirely of their living tissue, while larger ones can resist; once the black ring reaches the
less illuminated flanks of the colony, due to lack of light, the pregression of the disease comes to a halt.
In many cases the coral can fight BBD by producing an excess of mucus, thus starving the
cyanobacterium. Sometimes the mucal slime (consisting mainly of glycopeptides, thus mainly substrate),
can lead to an unwanted cultivation of carbon and nitrogen feeding microorganisms, dominated by
Desulvovibrio and Beggiatoa species in its final stages. Heavy microbial activity quickly lowers the
dissolved oxygen level of the closely surrounding waters, suffocating the delicate coral tissue
underneath. Only strong wave action or currents can save the coral by mechanically ripping off the slimy
coverage within days after formation. Although it is suggested that BBD may have a role in maintaining
coral diversity because it is most prevalent in coral species that form large colonies and provide a
structural framework for epibenthic organisms, BBD in combination with other diseases on a stressed
reef can have devastating effects.BBD has a higher rate of infection in warmer water. Thus, not only
seasonal temperatures, but anthropogenic disturbances as well (under eutrophic conditions even coral
species immune to it are attacked) affect the spread of BBD. Similarly, as in WDB, consequently coral
stocks suffering from BBD are also susceptible to tumors and parasitic worm infection.
Red Band Disease (RBD): as the name indicates, the "band" is a soft
microbial mat that is brick red or dark brown, not black, in color and
easily dislodged from the surface of the coral tissue. This disease
affects hard star, staghorn, and brain corals of the Caribbean and the
Great Barrier Reef. The band in RBD appears to be composed of
different cyanobacteria and microorganisms than those found in BBD
with even the microbial mat movement being different; the types of
microbes present might be altered depending on the coral host, but
little is known about this. Several scientists are studying the
composition of these microbial mats to determine how they differ
from BBD mats.
Black Overgrowing Cyanophyta (BOC): a number of other
cyanophytic species like Calothrix crustacea, C.scopulorum,
Hormothamnium solutum, Langbia confervoides, L.semiplena,
Phormidium spongeliae, and Spirulina subtilissima sometimes
simply overgrow the coral, thus, starving the polyps. But in other
cases they even actively penetrate and erode the coral skeleton,
leading to the structural collapse of branching corals. In some cases,
under eutrophic conditions, BOC is not only more common but may
even trigger WBD.
Black Aggressive Band (BAB): although similar in appearance to
BBD, the band material is somewhat thinner and appears gray rather
than black allowing the tissue-deprived coral to shine through. Recent
studies revealed another cyanobacterial genus (Spirulina) as one
possible cause, but it is not excluded that even a spirochete
Ballesteros sp. could be the main pathogenic agent. High
phosphorous contents in affected tissues suggest that eutrophication
may be one way to trigger of BAB, since its appearance is closely
related to shallow and coastal areas.
Fig. 114b Colpophyllia natans
(looks like Platygyra sp)
Fig. 114c Acropora sp. covered
with a carpet of overgrowing
cyanophyceae
, antonius fragen
Fig. 114d
Lethal Orange Disease (LOD): a yet unknown bacterial pathogen
causes death of the reef-building coralline algae Porolithon onkodes.
This coralline alga is the principle cementing agent that maintains the
intertidal wave-resistant reef crest. It helps the coral reef community
by cementing together sand, coral fragments, and other debris into a
suitable hard substrate for the establishment of coral colonies. It
absorbs wave energy in the outer reef rim that would otherwise erode
the shoreline and destroy many shallow-water reef communities.
LOD leaves the coralline algae skeleton white as it progresses in an
orange band, destroying the algae. When spreading, the front reaches
the margin of the algal thallus, it forms upright filaments and Fig. 114e Coralline lethal orange
globules, similar to those formed by terrestrial slime molds.
disease
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The globules can be caught by waves and easily spread to nearby coralline algae
Coralline Lethal Disease (CLD): it lacks the characteristic orange color of LOD, but is lethal,
nonetheless. CLD is apparent as concentric white circles surrounding patches of green filamentous algae
that have colonized the dead portion of the coralline algae Halimeda.
Fungal Infection (FI): fungal infestations on corals have been observed to
occur along with other pathogens. A lower phycomycetous fungus
has been associated with BBD in certain star corals (Montastrea
annularis); whereas BBD has been found to appear along with an
ascomycetous fungus. Other cases which involve a hyphomycetous
fungi (Scolecobasidium sp., Aspergillus sp.) are considered true
fungal infections that affect only massive or platy corals. It forms
necrotic patches (thus, termed also FIN) and reveal a zoned pattern.
The top layer of the necrotic patch is overgrown with epilithic algae,
sometimes intermingled with fungus. This is followed by a thin zone
of fungal growth giving way to a green band of shell-boring algae.
Beneath this strip lies a dense layer of fungal growth. The fungal
zones above and below the green band (only about 0.5 to 1.5cm in
width), appear brown to black and sometimes penetrate deeply into
the coral skeleton.
Yellow Band Disease (YBD also Yellow-Blotch Disease): it manifests
itself as a broad yellow band moving across healthy coral tissue in a
manner similar to the BBD. A band of decaying and sloughing off
tissue is observed. However, the entire area denuded by the infection
can retain the characteristic yellow color which can penetrate some
millimeters into the skeleton. The YBD appears to be in no way
similar to the aggressive LOD, which attacks coralline algae.
Investigations into establishing a pathogen are underway. Species
found to be affected by YBD are sclerectinians such as staghorn
(Acropora sp., Porites sp.), honeycomb corals of the family Faviidae,
plate corals (Turbinaria sp.), and even encrusting species of the
genus Montastrea.
Dark Spot Disease (DSD): it is based on increases in the occurrence of
lesions and observations of loss of tissue associated with the spots.
Dark purple to gray or brown patches of discolored tissue, often
circular in shape but also occurring in irregular shapes and patterns,
are scattered on the surface of the colony (bright purple patches have
also been seen on bleached colonies) or appear adjacent to the
sediment/algal margin of a colony. Sediment can accumulate in the
centers of these patches, with bare skeleton occasionally seen when
the sediment is brushed off. Investigations to isolate a distinct
pathogen have not yet been successful. It could well be that a
combination of pathogens may trigger this disease.
Fig. 115 Aspergillus colony on
Gorgonia ventalina
Fig. 116 Porites sp.
Fig. 117 dark spots on
Siderastrea siderea
Skeleton Eroding Band (SEB): a novel type of coral disease has been
identified on Indo-Pacific reefs. It is caused by Halofolliculina
corallasia, a new species of colonial, heterotrich ciliate that damages
the skeleton of the coral throughout the Indo-Pacific and the Red
Sea.. The syndrome is found on a wide variety of massive and
branching corals, and progresses similarly as in cases of BBD but it is
less dark and appears grayish rather than black. It feeds on bacteria
that nourish themselves from the coral tissue of the colony. The
skeleton eroding band consists of masses of black loricae (black
Fig. 118 Acropora sp.
shaped housings) of the ciliate, with bifurcated, beige wings sticking
out, resembling a bed of microscopic garden eels (about 200µm).
The dotted appearance of the white zone behind the front distinguishes SEB from BBD. SEB was found
on reefs of the Sinai (Red Sea), Mauritius, (Indian Ocean) and Lizard Island (Pacific, GBR).
Antonius
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Epizoism (EZ): Under certain circumstances, various epizoic organism were
observed to overgrow living sclerectinian corals. The phaeophyta
Lopophora variegata, the sponge Terpios hoshinota, the zoanthid
Palythoa sp., some ascidians (e.g. Didemnidae), or the octocoral
Erythropodium sp.. Although epizoism per se does not represent a
disease, but is rather associated with interspecific competition, it is of
perticular interest, as current antropogenically induced nutrient shifts
and global warming may induce booming reproduction of faster
growing epizoic organisms by upsetting the existing a/biotic balance
and ultimately altering a once flourishing coral reef from a "catch-up"
reef to a "give-up" reefs.
Fig. 119a Epizoic sponge
Peyssonnelia (PEY): among recently described syndromes of
epizoism on reef corals, one is caused by an unusual species of
corallinaceal Rhodophyta, Corallinaceae. It is Metapeyssonnelia
corallepida, a new species of a genus known only from the
Mediterranean Sea. This epizoic disease destroys corals on reef crest
areas, where it was not recorded at all 25yrs ago. M.corallepida is
capable of overgrowing entire corals, a process half accomplished on
the Millepora complanata. PEY forms a tightly attached "skin" on
the coral surface without a trace of coral tissue left below the algal
Fig. 119b Millepora complanata
cover.
PNEophyllum (PNE): A coralline red algal species Pneophyllum conicum
(Corallinacea) that like PEY overgrows and kills living corals. It
predominantly occurs from intertidal reef-crests to depths >30m; and
from sun-drenched upper reef surfaces deep into poorly illuminated
caves. The color of the alga tends to correspond to the exposure to
light (dark purple in the dark to gray at bright sites). It usually starts
from the dead basal portion of the coral colony (or cracks and
crevices) and expands its way up to the living portions. Usually this
corallinacea does not pose a threat to corals, but under certain
conditions (that still await demystification) can be quite lethal to most
Pocilloporidae, some Porites sp., and Faviidae ( Favia stelligera,
Favites complanata, F.abdita, F.flexuosa, Goniastrea retiformis fig.33, Platygyra daedalea, P.lamellina, Leptoria phrygia).
Fig. 120 Goniastrea retiformis
overgrown by
P. conicum
Diseases involving a combination of various diseases
White Syndromes (WS): a disease characterized by the combining effects
of WBD, TBL, and SDR. WS seems to be linked to the corallivorous
snails Drupella cornus or Coralliophila violacea. It is suggested that
WS-Drupella interaction occurs in three phases:
Phase 1: D.cornus snail, when occurring in low numbers, are
attracted by the disintegrating coral tissue and usually feed on the
exact interface of WBD.
Fig. 125 Drupella sp.
Phase 2: larger concentrations of D.cornus feed on healthy tissue at a
speed far exceeding that of WBD.
Phase 3: the impact of excessive feeding by D.cornus triggers SDR, destroying more coral tissue than is
occupied by snails; being stranded on a coral branch without tissue, the hords of D.cornus will move on
to new feeding grounds.
Mutations and other Tissue Abnormalities:
the white calcium carbonate skeleton of a hard coral is deposited by a thin layer of cells known as the
calicoblastic epithelium. Skeletal morphology is primarily controlled by genetics. The shape of the skeleton
which protects the colony of polyps varies with species, resulting in a number of characteristic shapes that allow
even the non-professional observer to distinguish between many coral species.
Skeletal deposition can change as a result of the actions of mussels, barnacles, christmas tree worms, and
commensal crabs, all of which may bore holes in the coral skeleton and cause the coral to change the pattern of
skeletal deposition. Other skeletal anomalies are caused by changes in the coral cells that deposit the carbonate
skeleton. Two such changes are hyperplasia and neoplasia (cancer).
Antonius
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Hyperplasia: a biological process that leads to an increase in the number of
cells in a tissue or organ, thereby increasing the bulk of the tissue or
the organ. A hyperplasm is a mass formed through the increase in the
number of cells. It appears that such growth originate from a single
budded polyp that undergoes localized, rapid growth, while retaining
functional fusion of its tissues with those covering the normal colony
skeleton.
Neoplasia: a pathologic process that results in the formation and
Fig. 126 Diploria clivosa
proliferation of an undifferentiated mass of cells. These cells grow
and multiply more rapidly than normal and lack the structural
organization and function of the normal tissue. These calcified
protuberant masses on branching corals have lost their normal
structure and have been shown to consist of undifferentiated
calicoblastic epithelial cells. A study of the stable carbon isotope
ratio of the calcium carbonate skeleton demonstrated that it was
deposited in a very different manner, being laid down much more
rapidly than normal; a finding consistent with the rapid metabolic rate
of the tumor. White, protuberant, irregularly shaped, calcified masses
or tumors, covered by a thin layer of translucent tissue, occur on the
surfaces of branches of Acropora spp. and other members of the
acroporid and pocilloporid families of hard corals.
The cells found in the tumor resemble the more metabolically active
Fig. 127 Acropora palmata
and rapidly dividing cells of the growing branch tips, and like the
branch tips, also lack the symbiotic algae. The epidermis covering the
tumor also loses the mucus secretory cells that help remove sediments from the coral surface. The result
is that sediment accumulations lead to tissue death and invasion of the skeleton by algae and boring
organisms. The presence of the tumors on a branch is also associated with a decrease in/or halting of
branch tip growth, suggesting changes in the transport of nutrients in the colony. This locally invasive
abnormal mass of tissue and unusually porous skeleton grows faster than the surrounding normal tissue
and skeleton. It proceeds to destroy the polyps and cause the death of the coral tissue. Based on these
factors, this condition has been termed a neoplasm (cancer), calicoblastic epithelioma.
Future outlook84:
the ever-increasing world population and its
dependence on natural resources are placing
new stresses on reefs at an accelerating rate.
While these systems are surprisingly
resilient, increasing levels of human impact
in the form of elevated nutrients and
sedimentation are taking their toll. Recent
episodes of coral bleaching have brought
national attention to the perils of tropical
Fig. 128 Coral reefs in danger over the next 40 years
reef systems. The outbreak of the Crown-ofThorns starfish (A.planci) on the GBR or the sudden die-off of the long-spined sea urchin (D.antillarum) in the
Caribbean have forced us to weigh the likelihood of these result from man-induced stresses versus natural ups
and downs in the organisms that populate our seas. The possibility that sea level may soon rise at a rate
exceeding the ability of present-day reefs to keep up is a further cause for great concern. The resulting impacts
on coastal populations that depend on the reef for food and protection from oceanic waves could be devastating.
Whether the goal is to better understand reefs and how they have evolved through time or to protect these
valuable ecosystems from increased degradation, places the processes discussed in this paper into a realistic
spatial and temporal framework which is of paramount importance.
Antonius
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Part V - References on the web:
Coral reefs general facts / introductions:
http://www-personal.umich.edu/~jbudai/reefs/geo100-syllabus.html
http://141.84.51.10/riffe/futura/futura1a.html
http://www.com.univ-mrs.fr/IRD/atollpol/ukintro.html
http://www.aquacare.de/info/veroeff/kuerif/riffe.htm
http://www-personal.umich.edu/~jbudai/reefs/geo100-syllabus.html
http://www.enchantedlearning.com/biomes/coralreef/coralreef.shtml
http://geo.uni-paderborn.de/seminare/saudi_arabien/achtze/achtze.htm
http://www.geology.iupui.edu/academics/CLASSES/g130/reefs/EO.htm
Picture gallery:
http://www-biol.paisley.ac.uk/biomedia/text/txt_pictures.htm
http://www.imagequest3d.com/catalogue/catalogues2.htm
http://www.holchanbelize.org/photos.html
http://www.puertogalera.net/ScubaDiveSites/Diving.htm
http://www.mantaray.com/cleaning_station/ocean_slide1.html
http://www.photolib.noaa.gov/reef/
Reef history: http://darter.ocps.k12.fl.us/classroom/klenk/Coral.htm
why to study reefs: http://www.uc.edu/geology/courses/coralreef/notes.htm
Part I - Cnidaria:
1
) http://www.indira.de/riff/riff.htm
2
) http://www.sbg.ac.at/ipk/avstudio/pierofun/transcript/riffe-bv.pdf
3
) http://www.einsamer-schuetze.com/natur/tierforschung/borstenworms/borstenworms.html
4
) http://www.nhm.ac.uk/hosted_sites/quekett/Special-reef.html
5
) http://cushforams.niu.edu/Forams.htm
6
) http://www.geocities.com/cotylorhiza/x_steinkoralle2.jpg
7
) http://egersund.asterisk.no/~emil/cnidaria/lophelia_pertusa.html
8
) http://atlantic.er.usgs.gov/habitat/openfile/htm/50.htm
9
) http://www.animalnetwork.com/fish2/aqfm/1997/jul/shell/default.asp
10
) http://www.science.ubc.ca/~geol313/lecture/reefs/rgrowth/rgrowth.htm
11
) http://www.sprl.umich.edu/GCL/paper_to_html/coral.html
12
) http://www.zoologie-online.de/Systematik/Metazoa/Cnidaria/hauptteil_cnidaria.htm
http://www.bio.swt.edu/Lavalli/guides/phylum_cnidaria.htm
http://www-personal.umich.edu/~jbudai/reefs/coral1.html
http://biosci238.bsd.uchicago.edu/Lab1.html
13
) http://www.sbg.ac.at/ipk/avstudio/pierofun/coral/family.htm
http://www.coralreefnetwork.com/stender/corals/rice/rice.htm
http://www.bishopmuseum.org/bishop/PBS/Oman-coral-book/
http://www.bishopmuseum.org/bishop/PBS/Oman-coral-book/Index/CorBkIndex.htm
14
) http://phylogeny.arizona.edu/tree/eukaryotes/animals/cnidaria/anthozoa/zoantharia.html
15
) http://www.ucmp.berkeley.edu/cnidaria/ctenophora.html
16
) http://www.paed-quest.de/oekoriff/content/qual_au.html
http://fp.redshift.com/pelagia/nematocysts.htm
http://www.gifte.de/quallen.htm
http://www.aqua.org/animals/species/jellies/bayjelly.html
http://www.bio.swt.edu/Lavalli/inverts/lecfold/cnidarians2.html
http://faculty.vassar.edu/~mehaffey/academic/animalstructure/outlines/cnidaria.html
http://www.shef.ac.uk/tldg/cnidnew/cndphylum.htm
17
) http://tidepool.st.usm.edu/crswr/trichocyst.html
18
) http://www.tennis.org/Special/lifecycle.html
19
) http://www.biol.vt.edu/Department/research/faculty/Opell/Biol4454/IZ%20Web%20copy/Cnidaria/trachylina.html
20
) http://www.biol.vt.edu/Department/research/faculty/Opell/Biol4454/IZ%20Web%20copy/Cnidaria/siphonophora.html
21
) http://www.biol.vt.edu/Department/research/faculty/Opell/Biol4454/IZ%20Web%20copy/Cnidaria/scyphozoa.html
22
) http://www.biol.vt.edu/Department/research/faculty/Opell/Biol4454/IZ%20Web%20copy/Cnidaria/cnidaria.html
23
) http://faculty.washington.edu/cemills/Hydromedusae.html
24
) http://www.biol.vt.edu/Department/research/faculty/Opell/Biol4454/IZ%20Web%20copy/Cnidaria/hydroida.html
25
) http://www.cyberphyla.com/hydrozoa/
26
) http://www.ucmp.berkeley.edu/cnidaria/hydrozoasy.html
27
) http://www.biol.vt.edu/Department/research/faculty/Opell/Biol4454/IZ%20Web%20copy/Cnidaria/hydrocorallina.html
28
) http://www.wetwebmedia.com/millepor.htm
29
) http://www.kheper.auz.com/gaia/biosphere/cnidaria/hydrozoa/Hydrozoa.htm
Antonius
67/70
30
) http://animaldiversity.ummz.umich.edu/accounts/physalia/p._physalis$narrative.html
) http://www.bio.swt.edu/Lavalli/inverts/lecfold/cnidarians1.html
http://fp.redshift.com/pelagia/illustrations.htm
32
) http://egersund.asterisk.no/~emil/cnidaria/index.html#schypozoa
33
) http://www.uni-hohenheim.de/~bahagish/Stauromedusae.htm
http://faculty.washington.edu/cemills/Stauromedusae.html
http://fp.redshift.com/pelagia/stauromedusa.htm
31
http://www.biol.vt.edu/Department/research/faculty/Opell/Biol4454/IZ%20Web%20copy/Cnidaria/stauromedusae.html
34
) http://fp.redshift.com/pelagia/aurelia.htm
35
) http://www2.hawaii.edu/~ortogero/jellyfish.html
http://www.bio.swt.edu/Lavalli/guides/cassio.htm
36
) http://fp.redshift.com/pelagia/cubozoa.htm
37
http://www.biol.vt.edu/Department/research/faculty/Opell/Biol4454/IZ%20Web%20copy/Cnidaria/semaestomeae.html
http://www.biol.vt.edu/Department/research/faculty/Opell/Biol4454/IZ%20Web%20copy/Cnidaria/rhizostomeae.html
http://www.biol.vt.edu/Department/research/faculty/Opell/Biol4454/IZ%20Web%20copy/Cnidaria/cubomedusae.html
) http://www.ucmp.berkeley.edu/cnidaria/Chironex.html
38
) http://www.ucmp.berkeley.edu/cnidaria/octocorallia.html
39
) http://www.smarterdesktops.com/MarineLife/what_are_they.htm
40
) http://www.biol.vt.edu/Department/research/faculty/Opell/Biol4454/IZ%20Web%20copy/Cnidaria/gorgonaceae.html
41
) http://www.seaslugforum.net/dendfeed.htm
http://www.aquarium.net/0998/0998_5.shtml
http://www.animalnetwork.com/fish2/aqfm/1997/nov/wb/default.asp
42
) http://www.ucmp.berkeley.edu/cnidaria/pennatulacea.html
43
http://www.biol.vt.edu/Department/research/faculty/Opell/Biol4454/IZ%20Web%20copy/Cnidaria/actinaria.html
) http://www.ucmp.berkeley.edu/cnidaria/actinaria.html
44
) http://www.ucmp.berkeley.edu/cnidaria/zoanthiniaria.html
45
) http://www.kheper.auz.com/gaia/biosphere/cnidaria/corallimorpharia/Corallimorpharia.htm
46
) http://www.uni-hohenheim.de/~bahagish/Ceriantharia.htm
http://ag.arizona.edu/tree/eukaryotes/animals/cnidaria/anthozoa/zoantharia.html
47
) http://porites.geology.uiowa.edu/database/corals/glossary/comorph.htm
http://www.biol.vt.edu/Department/research/faculty/Opell/Biol4454/IZ%20Web%20copy/Cnidaria/scleractinia.html
Part II – biology of cnidaria, structural elements and morphology
48
) http://www.a-m.de/deutsch/lexikon/mineral/carbonate/aragonit.htm
49
) http://www.enchantedlearning.com/subjects/invertebrates/coral/Coralprintout.shtml
http://www.cnidaria.org/cri/vocab.html
http://hypnea.botany.uwc.ac.za/marbot/coral_reefs/reef-building.htm (skeleton)
50
) http://www.pacificwhale.org/printouts/fsreef.html
http://library.thinkquest.org/25713/asex-a.html
51
) http://www.petsforum.com/IMA/CR13.htm
52
) http://www.bridge-rayn.org/aquatic%20curriculum/AqEnvCoursePres/index.htm
http://www.uncwil.edu/people/szmanta/research_8.htm
http://www.uncwil.edu/people/szmanta/research_10.htm
http://library.thinkquest.org/25713/sex-a.html?tqskip=1
http://www.animalnetwork.com/fish2/aqfm/1998/jan/features/1/default.asp
53
) http://ww2.mcgill.ca/Biology/undergra/c442b/lect19/1.htm
54
) http://porites.geology.uiowa.edu/database/corals/glossary/clform.htm
http://www.newcastle.edu.au/department/gl/corals/corals.htm
http://www.nmfs.noaa.gov/prot_res/PR/taxonomicfeatures.html
http://www.nmfs.noaa.gov/prot_res/PR/coralidmanualfront.html
55
) http://porites.geology.uiowa.edu/database/corals/glossary/clshape.htm
http://www.bishopmuseum.org/bishop/PBS/Oman-coral-book/Chap3/CorBkCh3htm.htm
http://www.sbg.ac.at/ipk/avstudio/pierofun/coral/morfacro.htm
56
) http://www.guam.net/pub/live_spawn/info.html
http://www.curacao-diving.com/diving/spawning.htm
http://www.gbrmpa.gov.au/corp_site/info_services/library/resources/reef_snapshots/coral_spawning.html
http://www.gbundersea.com/gallery1/gallery1.htm
http://www.fishid.com/learnctr/corspawn.htm
http://www.aims.gov.au/movies/spawning-01.html
57
) http://www.thekrib.com/Marine/tyree_rhythms92.html
58
) http://www-personal.umich.edu/~jbudai/reefs/coral4.html
59
) http://www.coexploration.org/bbsr/coral/html/body_life_cycle_story.html
http://www.aims.gov.au/pages/reflib/bigbank/pages/bb-09e.html
60
) http://www.datz.de/aktuell/titelgesch01_00.htm
Antonius
61
68/70
) http://www.jochemnet.de/fiu/OCB3043_38.html
http://www.ucmp.berkeley.edu/protista/dinoflagellata.html
http://cima.uprm.edu/~morelock/coralrf.htm
http://www2.uc.edu/geology/courses/coralreef/notes.htm
http://www.wfu.edu/users/derlme03/symbiosis/symbiosishtml.htm
http://mars.reefkeepers.net/Articles/AlguesSymbiotiques.html
http://www.jcu.edu.au/fmhms/school/pms/bchemmbiol/Academic_Staff/DY_LAB/Symbiodinium.html
http://mtlab.biol.tsukuba.ac.jp/WWW/taxonomy/Phytomastigophora/Dinophyta/Gymnodiniales.html*
http://www.nsm.buffalo.edu/Bio/burr/montipora.htm
) http://www.aquarium.net/0998/0998_4.shtml
Types of coral reefs
63
) http://school.discovery.com/homeworkhelp/worldbook/atozscience/c/133320.html
http://www.petsforum.com/IMA/CR06.htm
http://www.starfish.ch/Korallenriff/Riffarten.html
Part III - Reef zonation
64
) http://www.uark.edu/depts/geology/waterworld/dbmlreef2.htm
http://ozreef.org/reference/zonation.html
http://www.geo.lsa.umich.edu/~kacey/ugrad/coral8.html
http://cima.uprm.edu/~morelock/concept.htm
http://www.geology.iupui.edu/academics/CLASSES/g130/reefs/images/f1519th.gif
http://cima.uprm.edu/~morelock/7_image/20zoncar.gif
http://www.geology.iupui.edu/academics/CLASSES/g130/reefs/images/f1520th.gif
Flora
65
) http://www.com.univ-mrs.fr/IRD/atollpol/commatoll/ukalgato.htm
http://www.com.univ-mrs.fr/IRD/atollpol/ecorecat/ukalgues.htm
http://www.com.univ-mrs.fr/IRD/atollpol/ecorecat/ukalgesp.htm
http://www.coexploration.org/bbsr/coral/html/body_plants_algae.html
66
) http://orion1.paisley.ac.uk/courses/Tatner/biomedia/units/mino15.htm
http://www.ucmp.berkeley.edu/bryozoa/bryozoa.html
67
) http://www.sbg.ac.at/ipk/avstudio/pierofun/atmo/El-Nino.htm
fauna - invertebrates
http://www.nhm.ac.uk/zoology/taxinf/browse/family/family_browser.htm
http://www.coralreefnetwork.com/marlife/inverts/inverts.htm
http://phylogeny.arizona.edu/tree/eukaryotes/animals/animals.html
http://www.reefimages.com/Invertebrates_and_Scenes.htm
http://www.marineatlas.net/inverts/invertindex.shtml
http://www.graysreef.nos.noaa.gov/grhb/ecology.html (brief intro into reef ecology)
Food web on the reef
68
) http://www.coralreefnetwork.com/educate/shows/foodwebs/slide1.htm
http://www.reefs.org/library/talklog/e_borneman_051098.html
http://www-ocean.tamu.edu/~pinckney/PDF_627_01/Lecture_10.pdf
http://www.chez.com/easa/personal/pc/theorie/ff.html
Porifera
70
) http://animaldiversity.ummz.umich.edu/porifera.html
http://www.ucmp.berkeley.edu/porifera/poriferamm.html
http://salinella.bio.uottawa.ca/BIO2121/Lectures/BIO2121_lcts_Porif.htm
62
http://www.guam.net/pub/sshs/depart/science/mancuso/apbiolecture/27_Animalia/Porifera/porifera.htm
http://salinella.bio.uottawa.ca/BIO2121/Lectures/_PDFs/BIO2121_lct04_Porifera_00b.pdf (good graphics)
http://darwin.bio.geneseo.edu/~bosch/Coverpage/Courses/InvPorifera/sld001.htm
http://www.sidwell.edu/us/science/vlb5/Labs/Classification_Lab/Eukarya/Animalia/Porifera/
http://www-biol.paisley.ac.uk/courses/Tatner/biomedia/units/pori1.htm
http://www.seasky.org/reeflife/sea2a.html (good images)
Annelida
71
) http://www.museum.vic.gov.au/poly/terintro.html
http://www.nhm.ac.uk/zoology/taxinf/
http://www.nhm.ac.uk/zoology/taxinf/browse/family/terebellidae.htm
http://www.arl.nus.edu.sg/mandar/yp/EPIC/Terebellidae.html
http://www.reefimages.com/Worms/00000059.htm
http://www.graysreef.nos.noaa.gov/grhb/ecology.html
http://www-biol.paisley.ac.uk/courses/Tatner/biomedia/units/anne1.htm
http://www-personal.umich.edu/~jbudai/reefs/coral3.html
http://www.seasky.org/reeflife/sea2c.html
http://ozreef.org/directory/index.html#ANNELIDA
Antonius
69/70
Arthropoda
72
) http://www.seasky.org/reeflife/sea2e.html
http://www.livingreefimages.com/Page63a.html
http://ozreef.org/directory/index.html#CRUSTACEA
Mollusca
73
) http://www-biol.paisley.ac.uk/courses/Tatner/biomedia/units/moll1.htm
http://www.worldwideconchology.com/MarineGastropods.htm
http://nighthawk.tricity.wsu.edu/museum/Gastropods.html
http://www.gastropods.com/shell_pages/Taxon_pages/Class_GASTROPODA.html
http://www.wetwebmedia.com/gastropo.htm
http://research.amnh.org/invertzoo/research.html
http://divegallery.com/
http://webpages.shepherd.edu/PVILA/Oceanography/nudibranch.html
http://www.seasky.org/reeflife/sea2f.html (good images)
http://tolweb.org/tree/eukaryotes/animals/mollusca/cephalopoda/coleoidea/octopodiformes/octopoda/octopoda.html
Echinodermata
74
) http://www.coralreefnetwork.com/marlife/inverts/echinoderm.htm
http://www.botany.uwc.ac.za/presents/focuson/Urchin/
http://www.nhm.ac.uk/palaeontology/echinoids/index.html
http://www.sidwell.edu/us/science/vlb5/Labs/Classification_Lab/Eukarya/Animalia/Echinodermata/
http://phylogeny.arizona.edu/tree/eukaryotes/animals/echinodermata/echinodermata.html
http://www.ucmp.berkeley.edu/echinodermata/crinoidea.html
http://www.enature.com/search/show_search_byShape.asp?curGroupID=8&shapeID=1073
http://www2.uc.edu/geology/courses/coralreef/notes.htm
http://www.seasky.org/reeflife/sea2d.html
http://divegallery.com/crownofthorns.htm
Chordata
75
) http://fp.redshift.com/pelagia/tunicates.htm
http://animaldiversity.ummz.umich.edu/search/simple/
Chondrichthyes
76
) http://cas.bellarmine.edu/tietjen/images/cartilagenous_fish.htm
http://www.seasky.org/reeflife/sea2i.html
http://www.marineatlas.net/sw_fish/sharks.shtml
http://www.amonline.net.au/fishes/fishfacts/fish/oornatus.htm
Osteichthyes
77
) http://www.reefimages.com/Fishes.htm
http://www.angelfire.com/mi2/fishtank/index.html
http://cas.bellarmine.edu/tietjen/images/bony_fish.htm
http://nypa.uel.ac.uk/fish-bin/fishgen.pl?speccode=6380
http://www.wetwebmedia.com/acanthurTngs.htm
http://www.btinternet.com/~martytaylor/scuba/fish16.htm
http://www.fishbase.org/search.cfm
http://www.amonline.net.au/fishes/search.cfm
http://www.marineatlas.net/sw_fish/Fish_index.shtml
http://www.coralreefnetwork.com/educate/shows/slide_shows.htm
http://www.manband-archive.com/triggers/
http://www.amonline.net.au/fishes/fishfacts/specfam.htm
Reptiles (testudines)
78
) http://www.cyhaus.com/marine/reptiles.htm
http://www.seasky.org/reeflife/sea2j.html
http://animaldiversity.ummz.umich.edu/chordata/reptilia/testudines.html
Mammalia
79
) http://animaldiversity.ummz.umich.edu/chordata/mammalia.html
http://animaldiversity.ummz.umich.edu/accounts/megaptera/m._novaeangliae$narrative.html
http://www.seasky.org/reeflife/sea2k.html
http://animaldiversity.ummz.umich.edu/chordata/mammalia/cetacea/delphinidae.html
http://animaldiversity.ummz.umich.edu/accounts/trichechus/t._manatus_manatus$narrative.html
Antonius
70/70
Part IV - Environmental parameters
80
) http://www2.uc.edu/geology/courses/coralreef/notes.htm
http://www.co2science.org/issues/vol2/v2n15_co2science.htm
http://www.saj.usace.army.mil/projects/appbmareco.htm#_Toc488404214
81
) Workshop on Coral Bleaching, Coral Reef Ecosystems and Global Change: Report of Proceedings.
Organized by C.F. D'Elia, R.W. Buddemeier, and S.V. Smith. Maryland Sea Grant College
Publication. 1991).
Reef framework, calcification, construction and destruction (bioerosion)
82
) http://www-personal.umich.edu/~jbudai/reefs/coral5.html
http://state-of-coast.noaa.gov/bulletins/html/hab_14/intro.html
http://www.ots.ac.cr/rbt/revistas/suplemen/caribe2/antonius.htm
http://www.aquarium.net/0697/0697_1.shtml
http://life.bio.sunysb.edu/marinebio/coralreef.html
http://www.nmnh.si.edu/paleo/macintyre/belize.htm
http://www.chemecol.org/society/science.htm
http://www.sbg.ac.at/ipk/avstudio/pierofun/transcript/bioeros.pdf
coral diseases:
) http://www.sbg.ac.at/ipk/avstudio/pierofun/aqaba/disease1.htm
http://ww2.mcgill.ca/Biology/undergra/c442b/lect21/1.htm
http://www.broward.k12.fl.us/miramarhigh/guidance/mhssite/magnetmarine1/allymar.htm
http://www.broward.k12.fl.us/douglashigh/jpearcem2/jpearce5/mmccarthy5/disease.html (table)
http://www.nmfs.noaa.gov/prot_res/PR/coraldiseaseIDallcard.html
http://www.ots.ac.cr/rbt/revistas/suplemen/caribe2/hayes.htm
http://www.aspergillus.man.ac.uk/secure/news.htm
http://www.reefrelief.org/Image_archive/Coral_nursery/Elkhorn/Page4/CN1.html
http://www.es.cornell.edu/harvell/research.html
http://www.athiel.com/ybd/ybd.htm
83
http://www.sbg.ac.at/ipk/avstudio/pierofun/atmo/elnino.htm
http://www.solcomhouse.com/ElninoLanina.htm
http://www.marinebiology.org/coralbleaching.htm
http://state-of-coast.noaa.gov/bulletins/html/crf_08/national.html
Future outlook and reef threats
84
) http://cima.uprm.edu/~morelock/coralrf.htm
http://www.solcomhouse.com/coralreef.htm
http://www.epa.gov/owowwtr1/oceans/coral/biocrit/cont.html
http://coralreef.gov/threats.html
http://www.nodc.noaa.gov/col/projects/coral/coraldata/Coral_datasets.html
http://www2.uwsuper.edu/ccrs/Projects/Anchor_Assessment/Anchor_Damage.htm
http://www.yale.edu/roatan/soil.htm
http://www.reef.edu.au/ant/coralreefpaper.htm
http://www.uvi.edu/coral.reefer/threats.htm
http://www.marine.uq.edu.au/ohg/HG%20papers/Hoegh-Guldberg%20et%20al.%201997%20GBR.pdf
http://www.bishopmuseum.org/bishop/PBS/Oman-coral-book/Chap5/CorBkChap5.htm
http://www.reefs.org/library/talklog/e_borneman_051098.html
http://faculty.nl.edu/jste/Jamaica/reef%20presentation1.htm
http://esa.sdsc.edu/factcoral.htm
http://www.geology.iupui.edu/classes/g130/reefs/NG.htm (diving public)

Threats to and protection of coral reefs

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