The importance of phytoplankton for feeding corals

The importance of phytoplankton for
feeding corals
Text & Photos : José María Cid Ruiz
The whole of tropical coral species usually marketed and kept
in aquarium (Phylum: Cnidaria Class: Anthozoa), are taxonomically concentrated in a small number of orders (Subclass
Hexacorallia, orders: Sclerac!nia, Ac!niaria, Zoantharia, Anlcyo!phataria). Subclass Octocorallia, orders: Stolonifera, Alcyorists, in ponacea, Gorgonaria, Corallimorfaria) . Among aquarists,
pular language, are called "so! corals” those species that supility connec$ve $ssue
port individual polyps colony by a flexibility
(as is the case in Alcyonacea) or byy corneal !ssue such as gorgonians. Similarly, are referred
ed under the term "hard/stony
skel
sk
eletogenesis includes the forma$on
el
forma$
a$on
a$
on
corals" species whose skeletogenesis
(forme
med
me
d by aragonite at 90% and
d the
the rereof a hard structuree (formed
calcit
itee and
it
and magnesium
magn
ma
gnesium and stron$um
gn
um salts).
ssal
alts
al
ts).
ts
).
maining 10% by calcite
his hard skeleton
skele
leto
le
ton
to
n emerges
emer
em
erge
er
gess so
ge
so! connec$ve
connec
ec$v
$ve $s
$ssu
suee
su
Covering this
$ssue
that houses both individual
individua
uall polyps
ua
poly
po
lyps
ly
ps as
as different
diffe
di
fferent specialized
ffe
speci
cialized
ed cey. Hard
Har
H
ard
ar
d corals,
cora
co
rals, as iss well
ra
we known,
kno
nown, conlls belonging to the colony.
ir polyps
polyp
ypss are
yp
are popularly
popu
po
pularl
pu
rlyy known
rl
know
own
ow
n as "small
sidering the size of their
nd "large polyp
p yp coral
cor
oral
or
al " (LPS).
(LP
LPS)
LP
S)..
S)
polyp corals " (SPS) and
d corals also,
als
lso, we
ls
w can
n find
fin species
sp
Among so! corals and hard
zzooxa
xanthellae
xa
ae algae.
algae
ae.
ae
that host in their $ssues the famous zooxanthellae
elonging
ng in most
mo cases to
t the
These endosymbionts algae (belonging
llate algae)
alga
al
gae)
e) shares with its
i
genus Symbiodinium, a dinoflagellate
The importance of phytoplankton for feeding corals
host coral the organic compounds result of its processes of photosynthesis
(mainly glucose). Addi!onally, some of these corals also provide certain
es
essen$al
amino acids to the algae that are living with (N Satoh, 2011). In
contrast, many other species of so! and hard corals completely lacking
zooxanthellae in their $ssues. These la*er depend solely on its ability to
capture planktonic organisms to survive.
1
All rights reserved:
©José María Cid 2014
In a classic and simplified scheme, we would say that for corals
kept in aquarium, there are three basic models of feeding: a)
species that feed solely through their symbio"c algae (I refuse
to use the term “photosynthe"c feeding” or “photosynthe"c
corals”, b) species with mixed feeding strategy: organic compounds provided by the zooxanthellae algae supplemented
with planktonic organisms captured and c) species that feed
exclusively on pelagic organisms that capture.
Plankton capture by corals in categories “b” and “c” is considedered based almost exclusively on zooplankton organisms. The
various species of corals, depending mainly on the size of their
polyps, trap a wide range of prey (copepods, copepod nauplii,
ro"fers and even bacteria). In this vision about coral's diet,
ole, since it would not be a
phytoplankton have a secondary role,
direct source of food for coral , but it would serve to feed seveonic
on
ic prey and would be responsible
responsib
ible
le ffor
or
ral poten"al zooplanktonic
file of these
tthe
hese
he
se la#er. However some
me studies
sstu
tudi
tu
dies
di
es
the nutri"onal profile
ques"on this vision about
role
abou
ab
outt phytoplankton
ou
phyt
ph
ytop
yt
oplankton as a secondary
op
secon
onda
dary
da
ry rol
olee
ol
for feeding corals
le is the study
stud
udyy of Yahel
ud
YYah
ahel
ah
el G.
G. (G.
(G Yahel
Ya et al., 1998)
A good example
fieldwo
work conducted
ccon
ondu
on
duct
du
cted
ct
ed in the
th Gulf
Gulf of
of Aqaba
with an extensivee fieldwork
istrib
ibu!
u!on and
nd consump!on
ccon
onsu
on
sump
su
mp!o
mp
!on
!o
n of phytoplankphy
p
hyto
hy
topl
to
plankpl
(Red Sea) on the distribu!on
eefs
fs. In general
gener
eral
er
al terms
t ms the
he study
sstu
tudy
dy sshows a
ton in various coral reefs.
etwe
et
ween 20 and
and 60%)
60%) of the
th mass of
of phyphysignificant reduc"on (between
he sub-spectrum
sub
ub-sp
spec
sp
ectr
ec
trum
tr
um off species
specie
sp
iess below 8
ie
toplankton (in par"cular the
ton") in the
he waters
wat
aters that
at
that flow
ow
microns, "ultra-phytoplankton")
me rs in length
th dominated
dom
d
ominated
om
through a narrow reef channel five meters
roneph
phth
ph
thya
th
ya hemprichi and
by so* corals herbivores (Dendronephthya
The importance of phytoplankton for feeding corals
Scleronephthya corymbosa) resp
respect to concentra"ons of these same phytoplankton organisms in open water
w
nearby (seven-point sampling to five meters deep). The study's authors a#ribute the decrease of phytoplankton to
the capture of it by so* corals already men"oned, as well as preda"on by other organism
organisms belonging to different benthic taxa (bivalves, sponges, polychaete annelids).
The authors are not surprised of the fact that in the reef channel the dominant alcyonacea (Dendronephthya and Scleronephthya) are feeding on the
surrounding phytoplankton, since they are corals without zooxanthellae and
usually feed on phytoplankton. However, they considered a surprising result,
2
All rights reserved:
©José María Cid 2014
the fact that in the reef slope with absence of the so! coral
species men"oned above and dominant presence of hermatypic corals (reef-building stony corals), also was measured in this area a significant decrease in the concentra"on of
phytoplankton. The authors a$ribute this fact to the intake of
phytoplankton due to these hematypic corals, despite being
species with zooxanthellae in their "ssues and are not known
as species that feed on phytoplankton.
works cited
FABRICIUS, K. E., Y. BENAYAHU,
BENAYAH AND A. GENIN. 1995~. Herbivory in asymbio"c so! corals. Science 268: 90-92.
90
Flow-dependent herbivory and growth
A. GENIN, AND Y. BENAYAHU. 1995b.
199
corals.
Oceanogr. 40: 1290-1301.
in zooxanthellae-free so! ccor
oral
or
als.
al
s. Limnol.
LLim
im
and grazing near coral reefs
YAELl G. et al. 1998.
1998
98. Phytoplankton
98
Phyt
Ph
ytop
yt
opla
op
lank
la
nkto
nk
ton
to
n distribu"on
dist
di
Oceanogr.
1998,
Lmnol Ocea
eano
ea
nogr
no
gr.. 43(4),
gr
43
199
1
998,
99
8, 551-563
551
5
51-563
51
SATOH
genome to understand
SATO
TOH
TO
H N. et
e al.
al 2011.
2011
20
11. Using
11
Usin
Us
ing the Acropora
in
Acro
ropo
ro
pora
po
ra digi"fera
dig
d
ig
coral
cora
rall responses
ra
respon
re
onse
on
sess to environmental
se
eenvironment
ntal
nt
al change
ccha
hang
ha
nge Nature
Natu
Na
tu 476: 320–23
Based on the reading of this study and other similar
ar works
two conclusions seem to be able to extract:
For more informa•on
Fo
inf
nforma
nf
ma•o
•on or contact
•o
con
onta
on
tact
ta
ct the author: www.aqua•cnotes.com
www.aqua•
Within the complex trophic network
work of the reef, several
species of corals could be consuming phytoplankton
in a propor"on with
h respect to the consump"on of
zooplankton significantly
sign
gnifi
gn
ifica
ifi
cantly greater than it was thought.
ca
ttho
houg
ho
ught
ug
ht.
ht
The hermatypic
atypic ccor
corals
oral
or
alss could
al
coul
co
uld
ul
d also be poten"al consumers
con
onsu
on
sume
su
mers
me
rs
of phytoplankton,
phytoplankton
on,, despite
on
desp
de
spit
sp
itee the
it
the contribu"on
cont
co
ntri
ribu
bu"o
"on of organic
org
o
rgan
rg
anic
an
ic
carbon
on that perceive
percei
eive
ei
ve ffro
from
rom
ro
m th
thei
their
eirr sy
ei
symbio"c algae.
a
Reef aquariums, have
controllable
ve m
more cont
ntro
nt
rollllllab
able
ab
le condi"ons
ccon
ondi"o
on
"ons
"o
ns off experiexpe
ex
peripe
tural environment
tu
enviro
ronm
ro
nmen
nm
ent and
en
and therefore
theref
th
efor
oree offer
or
off
menta"on than the natural
an ideal environment to experiment
expe
ex
periment
nt with
wit
w
ith
it
h the
the usee of phytoplankton as part of the diet.
et. These experiences
experi
ex
riencess can
ri
ca help
he to
assess more precisely the importance
portance
ce of phytoplankton
phytopla
ph
lank
la
nkton
nk
n in the
diet of many species of coral kept in aquarium.
aquari
aq
rium.
ri
The importance of phytoplankton for feeding corals
3
All rights reserved:
©José María Cid 2014