comitetul de redacţie - Facultatea de Biologie

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Analele Științifice ale Universității „Al. I. Cuza” Iași, s. Biologie animală, Tom LVI, 2010
CHANGES IN THE STRUCTURE OF THE ROCKY MUSSELS
LITTORAL BIOCOENOSIS FROM THE ROMANIAN BLACK SEA
COAST
Adrian TEACĂ1, Tatiana BEGUN1, Victor SURUGIU2
and Marian-Traian GOMOIU1
1
National Institute of Marine Geology and GeoEcology – GeoEcoMar, Constanța Branch, 304 Mamaia Bd.,
900581, Constanța, Romania, [email protected]
2
“Al. I. Cuza” University Iași, Faculty of Biology, Bd. Carol I 20A, 700505 Iași, Romania
Abstract. The present study presents the results of researches conducted in the 2001-2009 period regarding the
hard substratum littoral biocoenosis from the Romanian Black Sea coast. On the basis of 280 quantitative
samples collected between 0 and 16 m depth from 10 sampling stations (from Cap Midia to Vama Veche), the
authors describe the qualitative and quantitative changes that took place in the rocky mussels‟ biocoenosis.
Keywords: Black Sea, rocky mussels‟ biocoenosis, qualitative and quantitative changes.
Rezumat. Modificări în structura biocenozei midiilor de piatră de la litoralul românesc al Mării Negre.
Studiul de față include rezultatele cercetărilor efectuate în perioada 2001- 2009 pentru biocenozele substratului
dur de mică adâncime de la litoralul românesc al Mării Negre. Pe baza a 280 probe cantitative prelevate în
intervalul de adâncime cuprins între 0 și 16 m din 10 stații (între Capul Midia și Vama Veche), autorii prezintă
modificările calitative și cantitative din biocenoza midiilor de piatră.
Cuvinte cheie: Marea Neagră, biocenoza midiilor de piatră, modificări calitative și cantitative.
Introduction
At the beginning of the 70s, the disturbances in the marine littoral ecosystems
occurred mostly under the anthropogenic stress leading to the decline of the biocoenosis
inhabited by the most important benthic communities of the Black Sea, amongst them
“Zernov‟s Phyllophora field” and deep banks of oysters and mussels, recognized as
unique, even at the worldwide scale. From local area perspective, the significant
transformations have been produced inside the benthic communities associated with
mobile substrata, nevertheless the hard substrata communities suffered alterations
comparing with their original character referenced before „70s period.
The unfavourable consequences following the ecological disequilibrium let the
way free for drastic reduction of specific diversity and more of that for biocoenoses
simplification/ homogenisation, especially on the NW shelf (Gomoiu, 1992, 1997, 1998,
1999). The main causes liable for decreasing the biodiversity of benthic communities at
the Romanian littoral between ends of the „60s till the „90s are:
 Extensive hydro technical constructions meant to consolidate the coastline,
which has generated rocky cliffs dislodgments provoking increased turbidity of
shallow waters.
 Eutrophication of the littoral waters.
 Amplification of mass development of phytoplankton giving so-called “algal
blooms”.
 Apparition year by year, on variable periods of time and on extended areas of
the hypoxia and/or anoxia phenomena, followed by mass mortalities of benthic
organisms.
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Adrian Teacă et al.
 Direct or indirect introduction of some allochotonous species (Rapana venosa,
Mnemiopsis leidyi, etc.) responsible for the oysters and mussels banks
decimation, collapse of fishing activities and extinction of autochthonous
species caused by opportunistic invasive species (Mya arenaria).
 Reduction of biodiversity due to the total disappearance of some species and/or
by population decrease of the others.
 Drastic reduction of sea-bed areas occupied by perennial algae such as
Phyllophora or Cystoseira.
 Changes in the sediment regime as a consequence of anthropogenic activities
made in hydrographical basins of the tributary rivers.
 Freezing phenomenon of coastal marine waters from the beginning of „70s.
At the end of the past millennium, the state of benthic ecosystems from the NW
part of Black Sea could be characterised by the following aspects:
 drastic reduction of the species richness;
 simplification of community structure leading to biocoenotic homogeneity;
 decrease of the abundance and biomass of large-bodied epibenthic species;
 diminishing of the filtering efficiency caused by the decrease of the filterfeeding populations‟ abundance;
 thriving of small-bodied infaunal opportunistic species (especially polychaets
such as Polydora cornuta, Capitella capitata, Melinna palmata, Alitta
succinea and oligochaetes);
 intrusion of some invasive species that led to undesirable consequences;
 quantitative fluctuations of all benthic populations.
Lack of ordinary monitoring of the epibenthic communities biodiversity state
after 70s has represented a considerable gap in the knowledge of communities‟ evolution
with no accountancies of the moments when populations of some species disappeared,
depleted or newly appeared.
Since the end of 90s, the biodiversity state at the Romanian coast seems to
undergo an improvement as it has been confirmed by the reappearance of some species
previously considered as rare or even disappeared. The contributing factors to these
positive changes are:
 Reduction of the eutrophication effect of the nutrients incoming into the
marine ecosystems.
 Reduction of the pollutants discharge from point sources (cities, shipyards)
where littoral biota was hardly impacted.
The incidence of populations playing the role of limiting factors was responsible
of regulating the effectives of some species (e.g. prey-predator relation). The predator
quickly decimates the prey species represented by reduced number of individuals,
especially if the latter has no natural enemies. Reserve must be kept in considering the
preyed species disappeared rather than rare under the influence of predator numerical
abundance. A real case for the pontic basin is given by the ctenophore Mnemiopsis leidyi
whose negative impact still impede upon the benthic and pelagic ecosystems equilibrium.
Material and Methods
For the study of the benthic fauna associated with rocky mussels‟ biocoenosis
from shallow waters, between 2001 and 2009, by means of autonomous or free diving,
have been collected 280 quantitative samples, distributed within 10 stations along the
Romanian littoral of the Black Sea situated between Cap Midia and Vama Veche. The
samples were collected by scraping off 400 cm2 quadrats using a knife with the blade of
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20 cm in length. The blade served also as the etalon for the delimitation of sampling areas.
The material collected was preserved with 4% neutralised formaldehyde.
In the laboratory all organisms were sorted under the stereomicroscope by major
taxonomic groups, identified as possible to the species level and counted.
For community structure analysis the abundance (A), the total number of
individuals (N), the total number of species (S), and the frequency index (F) were
calculated. Diversity of communities was calculated on the basis of the abundance data
matrix through Shannon-Wiener diversity index (H’) with logarithm base 2 using the
PRIMER 5 Program version 5.2.4.
Results and Discussion
The main changes noted in epibenthic system, witnessed for the positive longterm tendency of hard bottom communities‟ evolution, should be analysed from the
perspective of impact of changes occurred in littoral ecosystems to the associated
macrophytes and fauna.
From the qualitative point of view, macrophytes associations from the epibenthic
system, pass through a continuous amelioration indicated by the reappearance of the
brown and red perennial algae playing the role of sub-biocoenosis of the rocky mussels‟
biocoenosis.
The first mention for the appearance of some macrophytes species, pretty under
question, was the red alga Corallina officinalis, found by us in 1998 at the southern limit
of the Romanian seashore (fig. 1).
Figure 1. Corallina officinalis from 2 Mai-Vama Veche area in 2003 and 2009
(Photo: Balan S., Teacă A.).
Observations made in situ by SCUBA diving in at 2 Mai-Vama Veche area have
permitted us to estimate the percent cover of the substratum and its depth distribution. The
settled population presents a pronounced affinity for the calcareous platform of the
southern part of the Romanian littoral from the shallow water of 0.5-2.5 m depth, covering
35-65% of the total available substrate. Generally, these algae prefer the exposed part of
the substratum, against the water stream. Their strong adherence and compacted bushes
prevent the Corallina thalli to be washed out. The surfaces covered by the compacted
thalli of this species represent a particular biotope for the associated fauna not so well
adapted to high disturbing motion of water or direct exposure to sunlight, as for example,
in case of juveniles of Actinia equina (Fig. 2).
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Figure 2. Rocky mussels‟ biocoenosis. The main organisms associated with hard substratum from
shallow depth of the southern part of the Romanian littoral of the Black Sea (2 Mai-Vama Veche,
1998): 1 – Corallina officinalis, 2 – Halichondria panicea, 3 – Actinia equina, 4 – Actinothoe
clavata, 5 –Polydora websteri, 6 – Harmothoe imbricata, 7 – Capitella capitata, 8 – Janua
pagenstecheri, 9 – Lepidochitona caprearum, 10 – Mytilus galloprovincialis, 11 – Mytilaster
lineatus, 12 – Cyclope neritea, 13 – Balanus improvisus, 14 – Rhithropanopeus harrisii, 15 –
Pilumnus hirtellus, 16 – Botryllus schlosseri (original).
The maximum development of algae is reported for October-November.
Contrary, in summer period, Ceramium, Enteromorpha, and Cladophora colonized and
replaced Corallina, whose spread on the substrate was considerably reduced. The species
distribution at the Romanian littoral is fragmented, although in the southern part could be
found either in 2 Mai-Vama Veche area on the natural hard substrata or at Mangalia, on
the artificial substrata. Nevertheless, only in 2 Mai-Vama Veche area the population of
Corallina officinalis forms compact associations on extended surfaces in the shallow
waters. Thus, it is very possible that this species will found also in more northerly situated
locations, although in situ observations made at Eforie Sud, Costinești and Tuzla (20082009) haven‟t evinced this species. Bibliographic sources mention only southern part,
respective Vama Veche, as its area of distribution (Bavaru & Vasiliu, 1985). Recent
observations, made in 2008-2009, confirm once again the presence and distribution of the
species in the southernmost part of the Romanian littoral. Its population is well formed,
but often hided by annual species of algae. Being strongly attached to the substratum, the
species colonise the periodically exposed surfaces unravelled in situations of pronounced
wave-motion, which favour Corallina to get rid of epiphytic algae.
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Figure 3. Cystoseira barbata in the upper sublittoral (2.5 m depth) in 2 Mai-Vama Veche area in
2003 and 2009 (Photo: Teacă A.).
The qualitative structure of macrophytes has been enriched by reviving of
Cystoseira barbata bunches in the southern part of the Romanian Black Sea coast (Vama
Veche, Mangalia, Eforie Nord-Sud, Costinești, Tuzla) where does exist hard substrata
(fig. 3). The presence of this species in 90s is doubtful, but the presence of the thalli
thrown away on the beach confirmed that Cystoseira had constancy here, although in
much reduced number. Its presence in shallow waters creates a diversification of the
habitats, favouring the appearance of specific fauna associated to this endangered species.
Surveys made by SCUBA diving at Vama Veche and Mangalia in 2003-2005 showed that
the number of thalli of Cystoseira varied between 3 and 5 on the area of 15-20 m2 in
opened unprotected sectors, while it forms compact “meadows” in the sectors protected
by hydrotechnic constructions (dikes). The average height of the thalli was about 60-70
cm. In March 2005, the underwater observations have furnished information about the
abundance of this species in the cold period. There have been seen few thalli at the depth
of 2-2,5 m at 2 Mai-Vama Veche, fixed on the calcareous plate, with epiphyte red and
brown algae on it having for this reason a “woolly-like” aspect. The same appearance had
the thalli from the mussels‟ biocoenosis on the hard bottom from Mangalia. The mature
thalli of Cystoseira were encountered at 1 m depth along with the mussels‟ clumps and
other species of algae characteristic for cold-waters such as: Porphyra, Punctaria,
Scytosiphon and Ectocarpus. The actual character of growing and fragmented disposal of
the thalli does not provide enough arguments for considering the population as subbiocoenosis of the rocky mussels‟ biocoenosis. The few bunches relatively reduced as
height, with fragmented distribution, could be at most considered as atypical association.
Many of the reported observations of the Cystoseira thalli found on the shore at Eforie
Nord-Sud, Tuzla, and Costinești, in 2004-2009, evidenced that the population goes
through a certain remediation and tend to occupy its typical habitats for growing. Thus,
between 2008 and 2009 period the underwater observations made at Mangalia revealed a
considerable development of Cystoseira tufts in areas sheltered by dikes, stretching on
70% of the hard surfaces. The thalli had over 150 cm in length, forming a real thicket of
submerse vegetation.
We have done qualitative observations having in view the taxa whose
populations‟ evolution is still matter of time along with important observations regarding
the distribution in depths of mass species. In the period 2003-2005 the greatest depth at
which Ceramium occurred was 4-6 m, deeper than in 90s. The recent observations (20082009) showed an extension of its distribution down to 8 m isobath, proving the increasing
of the water column transparency, enough to stimulate the bioactivity of some photophilic
species.
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From qualitative point of view, the macro- and meiofauna associated with the
hard substrata did not register significant changes as compared to period 60-70s, which
denote stability and normal coenotic development of epibenthic system, out of external
perturbation factors. The qualitative differentiations are visible when the structure of
populations is analysed comparatively with those of the last decade, characterized by
simplicity and the absence of the certain forms whose population size, even in normal
conditions, is usually small. The qualitative enrichment of associations from hard
substrata is a positive sign for amelioration of littoral ecosystems thanks to environmental
quality improvement.
The main species with uncertain distribution in the past decade, but with normal
development in the present are superior crustaceans such as amphipods, cumaceans,
mysidaceans, natant and reptant decapods. Apart from these taxonomic groups, is taking
place a reviving of populations of some extremely sensitive species to the conditions
offered by the hard bottoms biotopes. The populations of sea slugs (Nudibranchia) give
the most eloquent example with a surprising evolution at the Romanian littoral.
The taxa whose effectives were much reduced or even absent in the previous
years and which in the present forms well-established populations at the Romanian littoral
are:
- Opercularella lacerata (F=25%) (Hydrozoa),
- Ventromma halecioides (F=30%) (Hydrozoa),
- Tergipes tergipes (F=50%) (Nudibranchia),
- Syllis gracilis (F=59%) (Polychaeta)
- Nereis zonata (F=41%) (Polychaeta)
- Ericthonius difformis (F=40%) (Amphipoda),
- Jassa ocia (F=50%) (Amphipoda),
- Siriella jaltensis (F=20%) (Mysidacea),
- Athanas nitescens (F=-60%) (Decapoda),
- Palaemon adspersus (F=20%) (Decapoda),
- Pisidia longicornis (F=70%) (Decapoda),
- Eriphia verrucosa (Decapoda).
Rare species, with singular appearances, cited as disappeared in the last years in
epibenthic system, are:
- Limapontia capitata (Nudibranchia) and
- Cymadusa crassicornis (Amphipoda).
Superior crustaceans populations, previously recorded as having reduced
effectives or with sporadic appearances in just few areas, now are abundant in other
locations from Romanian littoral (Begun, 2006; Teacă et al., 2006a). The main species
within this category are:
- Amphitoe ramondi (F=83.33%) (Amphipoda),
- Apherusa bispinosa (F=23.81%) (Amphipoda),
- Caprella acanthifera (F=7.14%) (Amphipoda),
- Dexamine spinosa (F=19.05%) (Amphipoda),
- Dynamene bidentata (F=32.14%) (Isopoda),
However, Apherusa bispinosa and Caprella acanthifera cannot be considered as
fully belonging to epibenthic system because their populations are predominantly settled
in deeper zones.
An important result of this study is that of revealing the state of some populations
belonging to species with rare occurrence, such as nudibranch molluscs. Most of the
species from the Romanian waters have been identified in 60-70s period (Gomoiu, 1961;
Müller et al., 1965). The subsequent mentions are practically inexistent most probably
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because of the pretty little concern given to this group. The sensibility of this group to
external disturbing factors (pollution) represents one of the possible causes which have
determined the reduction of population size almost to the disappearance. The small bodysize and their fragility in contact with preservation agents impede upon correct taxonomic
identification, which explains the gap in the studies dedicated to this group.
The most cited species at the Romanian littoral have been cited on deep
sedimentary bottoms, although in other sectors of the Black Sea the same species were
seen both on hard bottoms and on thallophytes or on phanerogames bushes.
Between 2001 and 2004 the only species identified on hard seabed at the
Romanian Black Sea coast were Tergipes tergipes and Limapontia capitata.
The most important faunistic element of this category is Tergipes tergipes, which
is found anywhere in epibenthic associations and is constituted of large populations,
unlike than in the previous quotations (Fig. 4).
Figure 4. Tergipes tergipes (preserved material) (Photo: Teacă A.).
For the first time, we have indicated this species exclusively in Constanta sector
(Cazino Mamaia) since 1998. Actually, the distribution of this taxon has been
considerably laid out towards the south, being met in great number at Agigea and Eforie
Nord-Sud.
The abundance of its population ranges between 25 and 5,000 ind.m-2 (!), with an
average of 100 ind.m-2. The maximum limit of distribution in depth on artificial hard
substratum is 16 m (at Agigea). The maximum abundance has been recorded at 0-6 m
depth, being little bit more numerous in autumn season (Fig. 5).
1
10
DAVG ind.m-2
100
1000
10000
0
2
Depth (m)
4
6
8
10
12
14
June
O ctober
16
Figure 5. Seasonal variation of abundances of Tergipes tergipes population along depth gradient on
the Agigea dike (2004).
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Another reviewing for Romanian malacological fauna consists in the
reappearance of Limapontia capitata (Fig. 6). This species used to be very common in the
hard bottom biocoenosis from the southern part of the Romanian Black Sea coast. It
prefers the mesoporal interstices within the mussels‟ colonies or macrophytes, some time
ago being considered the most abundant nudibranch in rocky infralittoral between Agigea
and Eforie Sud (Müller et al., 1965). The absence of records after 1975 forces us to admit
that this species was very rare or even completely disappeared at the Romanian littoral for
a long period of time. In our samples, the species appeared on the artificial hard bottom
from Agigea in June 2004, at 6 m depth. The size of the specimen found is comparable
with the values given by bibliographical sources (Müller et al., 1965): 2 mm in length and
1 mm width (preserved material, contracted). This Boreo-Atlanto-Mediterranean species
prefers the algae bushes of Ulva, Enteromorpha, Cystoseira or Ceramium, presenting the
homochromic colouration with the substratum. In spite of that, we have identified this
species in the epibenthic association dominated by hydrozoans Gonothyraea loveni and
Hartlaubella gelatinosa.
Figure 6. Limapontia capitata (Agigea, 2004) (l – lateral, v – ventral, preserved material)
(Photo: Teacă A.).
Worth to be mentioned is the case of invasive nudibranch Corambe obscura that
extended its area within the epibenthic associations from the Romanian littoral. This
species was brought out for the first time in the Constanta area by the end of 90s. Since
then the species continuously extended its distribution in Romanian waters (Gomoiu &
Skolka, 1997). In the present, it is a common faunistic element in epibenthic associations
from Cap Midia to Eforie Nord, with average abundance of 35 ind.m-2 (Fig. 7).
Figure 7. Corambe obscura (d – dorsal, v – ventral, preserved material) (Photo: Teacă A.).
The qualitative structure of nudibranchs within epibenthic system of the
Romanian Black Sea coast could be represented by a greater number of species. In
samples collected there were specimens that couldn‟t be identified to the species level. We
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could not exclude the probability that those specimens belong to Tergipes or Embletonia
genera (Fig. 8). A detailed reviewing will certainly clear up this problem especially in the
situation that the abundance and distribution of this group pass through an important
growth in the northwestern part of the Black Sea.
Figure 8. Nudibranchia indet. (preserved material) (Photo: Teacă A.).
The most important differentiations in respect with the situation from 60s
(Băcescu et al., 1963; Băcescu et al., 1971), 70s (Țigănuș, 1979), 80s (Gomoiu, 1982,
1986, 1989) and 90s (Țigănuș, 1992; Gomoiu, 1992) refer to qualitative structure of
macrofauna of superior crustaceans (reptant and natant decapods). The decapods recorded
at the Romanian littoral inhabit mostly the upper infralittoral, associated with
characteristic biotopes. Both, worsening of characteristic habitats and environmental
conditions and collecting methods in some cases, carries the responsibility for the
disappearance or rareness of some species. The bared ecological niches had determined
the overspread of opportunistic species resistant to any kind of changes occurred in
benthic biocoenosis. As well, the littoral ecosystems instability enhanced the expansion of
ubiquitous species at Romanian littoral, among them Rhitropanopeus harrisii, rare until
80s (Guțu, 1980). This species has successfully invaded biocenoesis with soft and hard
substratum from shallow depths, now being a common species.
There are two species of natant decapods recently reported in rocky mussels‟
biocoenosis, extremely rare so far (Guțu, 1980; Petrescu & Bălășescu, 1995). The former,
Palaemon adspersus, has been identified many times in different locations (Pescărie,
Mamaia, Eforie Nord, 2 Mai-Vama Veche) in 2002-2003 (Teacă et al., 2006c). Still, its
random appearance in samples, as well as its total absence in 2004 or in the second part of
90s in Eforie Nord and Eforie Sud area (Petrescu & Bălășescu, 1995) followed by
spontaneous appearances in 1993-1994 and in 2002-2003, is not meant to frame this
species to a certain ecological status.
The later species, predominant in shadowed places, is the small sized Athanas
nitescens, which registered an extraordinary recovery and now is practically found in
every sample collected from hard substratum (Fig. 9). In 1993-1994, the researches
conducted had not revealed the presence of this decapod at the Romanian littoral (Petrescu
& Bălășescu, 1995), as long as in 1980 the species has been considered as rare (Guțu,
1980).
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Figure 9. Athanas nitescens, ♂ (preserved material, Agigea) (Photo: Teacă A.).
The actual average densities of this species ranges between 50 and 100 ind.m-2,
and it span down along a bathymetric profile from 1 to 20 m (Fig. 10). The maximum
abundance, exceeding 180 ind.m-2, was recorded between 6 and 10 m depth (Fig. 11). The
species was found in many places from the Romanian coast. The most abundant
populations were found at Constanța, Agigea and Eforie Nord.
250
1977
2002-2004
DAVG ind.m-2
200
150
100
50
0
0
2
4
6
8
Depth (m)
10
12
14
16
Figure 10. The average seasonal abundance of Athanas nitescens population along depth gradient in
the Agigea area (2002-2004), comparatively to the observations made in 1977.
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0
50
100
DAVG ind.m-2
150
200
250
300
350
0
2
Depth (m)
4
6
8
10
12
14
June
O ctober
16
Figure 11. Seasonal abundance of Athanas nitescens on vertical profile from the Agigea dike
(2004).
As for the reptant decapods, rare in the period 80-90s, the small anomur Pisidia
longicornis fell under this category (fig. 12). The qualitative analysis of the decapods
accomplished in 1993-1994 period (Petrescu & Bălășescu, 1995) has confirmed the
absence of this species in the littoral hard substratum biocenoesis. Further researches in
different locations (Constanța, Agigea, Eforie Nord-Sud, Mangalia, 2 Mai-Vama Veche)
came to a similar conclusion. It is possible that the species populations were small in
number, settled in deeper areas than 4-5 m, far from the shore. Other hindering causes
might be the unsuitable collecting methodology from the hard substratum and the species
preference for the shadowy places.
Figure 12. Pisidia longicornis, ♂ (preserved material, Agigea) (Photo: Teacă A.).
First analyses regarding the quantitative parameters have been done in 2001 in
Agigea zone from 2 m in depth (Teacă et al., 2006b). The further researches (2002-2004)
have confirmed the presence of this decapod species in almost all locations with hard
substratum, from Cap Midia to Vama Veche, implicit on dikes, where it has extremely
abundant populations (Agigea). The most abundant populations have been observed in
Constanta and Agigea area. Toward the south (Mangalia zone), its abundance is getting
much lower. On Agigea dike, the average densities reached to 375-550 ind.m-2 between 1
to 20 m depth. Maximum abundances were registered between 6 and 10 m, exceeding
1,000 ind.m-2 (Fig. 14). The current densities are fifty times superior to those known from
the literature (Fig. 13).
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800
1961
2001-2004
DAVG ind.m-2
600
400
200
0
0
2
4
6
8
Depth (m)
10
12
14
16
Figure 13. The average seasonal abundance of Pisidia longicornis population along depth gradient
at Agigea (2001-2004), comparatively to the observations made in 1961.
0
200
400
DAVG ind.m-2
600
800
1000
1200
0
2
Depth (m)
4
6
8
10
12
14
June
O ctober
16
Figure 14. Seasonal abundance of Pisidia longicornis population on vertical profile from the
Agigea dike (2004).
Eriphia verrucosa is a reptant decapod whose populations are low in number, but
constantly present on the hard bottom habitats (fig. 15). It has been considered rare in 80s
(Guțu, 1980) and not found in the early 90s (Petrescu & Bălășescu, 1995). Its cryptic
behaviour and the preference for ruffled biotopes underlaid deeper than 2-3 m often
hamper its observation. But, it surely represents a constant faunistic element in benthic
associations from southern part of the Romanian littoral (Agigea, Costinești, Tuzla,
Mangalia, 2 Mai-Vama Veche). Its presence has been noted since 90s (Mustață et al.,
1998) in Agigea area. After that, the species has been found many times in 2 Mai-Vama
Veche (2001-2005) and also, in rocky associations from Cap Midia in 2002. It might be
said that this decapod population follow a normal spatial and temporal dynamic, low
abundance but constant presence being typical for this big-sized species.
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Figure 15. Eriphia verrucosa, ♂ (preserved material, Mangalia) (Photo: Teacă A.).
From qualitative point of view in 2001-2004 the number of crustacean species in
rocky mussels‟ biocoenosis has been greater with at least 19 taxa than in the last decade
(1993-2001). Thus, there were 50 taxa (except copepods) between 2001 and 2004, a value
greater even than that cited in the literature for the period 1972-1979 (Teacă, 2006). These
values are only comparable with those reached by the associations from the hard
substratum from Agigea in 1961 (Băcescu et al., 1963).
To our knowledge about the evolution of epibenthic populations, the actual
qualitative structure of dominant species of the fauna associated to rocky seabed
(artificial/natural) has not changed significantly over the last 2-3 decades. The very
important differences have been recorded with respect to the meiofauna as well as with
the respect of epibenthic macrofauna from quantitative point of view. Thus, average
values of population abundances in 2004 have been at least 5-10 times greater than in the
period 60-70s. However, this fact is not necessarily reflecting a radical improvement of
the structure of the epibenthic system but a remediation of already existent populations
along with reappearance of some taxa declared before as vanished, comparative to 80-90s
decade.
At the end of 70s and the whole 80-90s period, known as the most unstable
period from ecological point of view, the average densities of epibenthic populations, both
sessile and vagile, from shallow waters have been oscillated between 163,352 ind.m-2 and
264,000 ind.m-2 on dikes in Mamaia and Constanta Harbour (Gomoiu, 1988, 1989) or was
in average of 189,276 ind.m-2 in Agigea zone (Țigănuș, 1979). In the period 2003-2004,
the average density of zoobenthos varied between 1,300,000 and 2,100,000 ind.m-2. The
numerical difference between the periods is given by the extremely abundant meiofauna,
represented by the nematodes and harpacticoids, whose densities often exceeded 600,000800,000 ind.m-2. The abundances for some major taxonomic groups in period 2001-2004
are numerically similar with those from 1961 from Agigea (Băcescu et al., 1963) and to
those from the fouling of the ships, with estimated values of 500,000-1,500,000 ind.m-2
for vagile meiobenthic forms as nematodes and copepods (Gomoiu & Țigănuș, 1974).
Still, the average abundance of epibenthic populations from Agigea in 1961 was 288,613
ind.m-2, much lower than from the period 2001-2004 (Teacă, 2006).
So, the number of individuals of epibenthic organisms, both on artificial and
natural hard substratum, has evolved toward a higher abundance in the last years
-19-
comparatively with ecological crisis period of 80-90s. This was happened within all major
taxonomic groups of epibenthic invertebrates from rocky mussels‟ biocoenosis.
Insignificant variations were recorded in the case of average biomasses of
zoobenthos and also in the case of molluscan fauna from Mamaia and Mangalia whose
values of 20,540 g.m-2 and respectively 16,680 g.m-2 are comparable with those cited in
the literature (Gomoiu, 1988).
If the molluscs are excluded, the average values for the other epibenthic groups
present small variations depending on location. Thus, the average values recorded at
Mamaia in 2003 and 1988-1989 (on artificial substrata) have been of 19,846 g.m-2 (wet
biomass) respectively 17,175 g.m-2 (wet biomass), while the differences from quantitative
point of view have been recorded only for worms and crustaceans. The average biomass
value of 19,780 g.m-2 (wet biomass) from Mangalia zone is similar to that from Mamaia.
Generally, the biomass values are greatly influenced by the abundance of barnacles, which
can overwhelm the other benthic groups, which lack calcareous structures. The
contribution of barnacles weight was 120 g.m-2 in the period 2001-2004 and 220 g.m-2 in
1977.
Worms, molluscs and crustaceans have recorded the most profound quantitative
changes in the case of epibenthic associations in shallow waters. The 80 - 90s represents
the most disturbing period for coastal ecosystems having negative consequences on
epibenthic structure dominated exclusively by meiobenthic worms (Nematoda) and
opportunistic polychaetes (Polydora cornuta, Capitella capitata, Alitta succinea) capable
to resist to eutrophication of marine environment of that period (Surugiu, 2005).
Crustaceans and molluscs have registered a dramatic decline both as number of
species and as populational abundance. In spite of that, before the eutrophication period
and after that, the numerically dominant species within crustaceans were Harpacticoida,
Microdeutopus gryllotalpa, Melita palmata and Balanus improvisus.
Mollusca
12%
Vermes
51%
Mollusca
9%
Crustacea
32%
Vermes
72%
Crustacea
17%
Varia
2%
Varia
5%
1977
1988-89
Mollusca
6%
Vermes
38%
Crustacea
54%
Varia
2%
2003
Figure 16. Proportion of epibenthic populations in associations on the hard bottoms in the shallow
depths at the Romanian littoral between 1977 and 2003.
-20-
Comparative periodical analysis shows a profound destabilization of populational
equilibrium of benthic invertebrates based to exclusive dominance of worms in spite of
the other groups. Actually the hard bottom associated fauna ranges between normal limits
of evolution especially by enrichment of vagile fauna, which demonstrate the ecofunctional maturity of any natural aquatic system (fig. 16) (Teacă, 2006).
Conclusions
The extraordinary complexity of the epibenthic system from both shallow and
deep waters, as well as its role in the marine ecosystems must beneficiate of a very
detailed knowledge of its components (qualitative structure) along with its variations in
time and space.
Holistic comparative analysis of shallow waters‟ epibenthic associations in the
period 2001-2009 have permitted us to evince the important aspects regarding the
distribution and the abundance of epibenthic system. This fact has permitted us to
appreciate the evolution of littoral biocoenoses in the context of changes that took place in
the Romanian coastal zone.
Comparing the information about the structure of hard bottom benthic fauna
associations (both artificial and natural hard substrata) and that of soft bottoms fauna with
those of the epibenthic populations for 2-3 decades ago it is observed that there have not
been registered significant qualitative changes of dominant species. The high diversity
from studied locations could be compared (in case of some supra-specific groups) with the
state of benthic populations from 1960-1970.
The most important differences have been registered by meio- and macrobenthos
with regard to the quantitative parameters. This does not necessarily reflects a radical
improvement of qualitative structure of epibenthic communities rather than an
amelioration of existent populations and the reappearance of some disappeared taxa,
comparing to 80-90s status. However, the improvement of benthic system quality depends
most of all on the amelioration of pelagial system quality such as the increasing of water
column transparency so as to hold at proper parameters the activity of macrophytes
species bellow 10 m deep.
Acknowledgements
This study was partially fulfilled by the support from the research grant PN-IIID-PCE-2008-2/No. 116 from the National University Research Council (CNCSIS).
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comitetul de redacţie - Facultatea de Biologie

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