Biocenosis Of Modiolus Phaseolinus In The Area Before The Kerch Strait Of The Black Sea
BIOCENOSIS OF MODIOLUS PHASEOLINUS IN THE AREA BEFORE THE KERCH STRAIT OF THE BLACK SEA
A.S. Terentijev
Southern Scientific Research Institute of Marine Fisheriesand
and Oceanography (YugNIRO), Kerch, Ukraine
During last decades the Вlack Sea area is under strong antropogenic pressure and as a result of which the degradation of natural ecosystem is observed.
In the present work the YugNIRO\’s data collected during 5 expeditions
1986-90 were used. The benthic sampling were made by "Ocean" and "Petersen" dredgers at the depths range 10-100m. The taxonomic processing was carried out by "The key of the Black - Athov Seas fauna" [1]. During all periods of the investigations 340 stations were carried out at the area 5.3 thousand km2. While calculating the average indices of abundance and biomass were taken. Species stability was expressed by a formula С=100р/P, where p - samples number containing this species, P - general number of samples. Depending on value (С) the following species categories were distinguished: > 50% - constant, 25-50% - additional,
Biocenosis of Modiolus phaseolinus was at the depths > 40m on the phaseolinus silt (mixed with gray silt of phaseolinus shells). In 1986 biocenosis made up 37% of whole area of the Kerch stsait before the Black Sea. There were 45 species of animals in biocenosis composition: 10 - Bivalvia, 3 - Gastropoda, 12 - Polychaeta, 8 - Porifera, 5 - Ascidiacea, 3 - Crustacea, 2 - Echinodermata, Coelenterata and Nemertini by one species (Table 1.).
Ophiuroidea - A. stepanovi, solitary six-rayed coral P. solitarius and polychaeta T. stroemi were typical of the biocenosis. M.I. Kiseljova also
pointed these species as typical ones of this biocenosis [5, 6]. Species richness of the biocenosis decreased with the depth increasing. Much more species were observed at its upper part, where there were many animals, typical of the biocenosis of M. galloprovincialis. This biocenosis was situated much higher. The species richness swiftly degraded till the depth of 70-80m (Fig. 1). At the 70m all species of porifera, crustacea, gastropoda, holothurioidea, many species of polychaeta disappeared. At the depth of 100m only 16 species of animals were observed.
Table 1. The composition and an average level of development of biocenosis of M. phaseolinus in the area of the Kerch Strait before the Black Sea
Species
Average abundance, sp./m2
Average biomass, g/m2
Constant:
Modiolus phaseolinus
Terebellides stroemi
1180,000±250,000
8,200± 1,400
121,000±28,000
0,820± 0,380
Sum
1190,00±250,00
122,000±28,000
Additional:
Amphiura stepanovi
Pachycerianthus solitarius
8,000± 1,700
2,100± 0,540
0,171± 0,045
0,430± 0,110
Sum
10,100± 1,800
0,600± 0,120
Rare:
Abra renieri
Acanthocardia paucicostata
Calyptraea chinensis
Ctenicella appendiculata
Disidea fragilis
Eugira adriatica
Haliclona angulata
Haliclona gracilis
Haliclonissa digitata
Melinna palmata
Modiolus adriaticus
Molgula euprocta
Mycale syrinx
Mytilus galloprovincialis
Nephthys hombergii
Nereis longissima
Notomastus latericeus
Phyllodoce maculata
Pitar rudis
Plagiocardium papilosum
Plagiocardium simile
Stereoderma kirchbergi
Synisoma capito
0,108± 0,077
0,150± 0,110
0,200± 0,160
1,180± 0,290
0,220± 0,140
0,230± 0,140
0,150± 0,110
0,390± 0,210
0,460± 0,370
1,040± 0,320
0,147± 0,083
0,290± 0,150
0,150± 0,110
0,340± 0,250
1,090± 0,350
0,370± 0,170
0,950± 0,160
0,420± 0,180
0,111± 0,079
0,890± 0,830
0,240± 0,140
1,660± 0,520
0,590± 0,320
0,010± 0,007
0,009± 0,006
0,025± 0,019
0,390± 0,130
0,012± 0,007
0,031± 0,021
0,046± 0,043
0,024± 0,015
0,130± 0,100
0,034± 0,013
0,119± 0,069
0,160± 0,120
0,122± 0,098
0,930± 0,820
0,115± 0,049
0,140± 0,110
0,054± 0,018
0,005± 0,004
0,049± 0,036
0,170± 0,160
0,028± 0,017
0,380± 0,110
0,029± 0,013
Sum
11,400± 1,400
3,020± 0,890
Very rare:
Abra nitida, Amphitrite gracilis, Capitella capitata, Cerastoderma glaucum, Ciona intestinalis, Haliclona pallida, Gammarus subtipicus, Nemertini g. sp., Nephthys cirrosa, Nephthys longicornis, Nereis diversicolor, Phyllodoce vittata, Sphaeroma pulchellum, Suberites carnosus, Suberites prototipus, Sycon ciliatum, Tritia reticulata, Trophonopsis breviata
Sum
1,310± 0,360
0,164± 0,065
Total sum
1210,000±250,000
126,000±28,000
Fig. 1. Species richness of biocenosis M. phaseolinus at different depths.
Biomass and abundance of animal benthos had also higher values at upper part of biocenosis (Fig. 2). From 60m till 75m fast decrease of these indices was observed. Some decrease of abundance and animal benthos biomass till 45m of depth, was explained, may be, by competition between M. phaseolinus and M. galloprovincialis.
Fig. 2. Average indices of abundance (a) and biomass (b) of animal benthos of the biocenosis of M. phaseolinus.
The dominant species made up 98% of abundance and 97% of animal benthos biomass. That is why in spite of rather high species richness, species variety of this species turned out very poor. The biocenosis with evident domination of little number of species were called by A.A. Shorygin peaked ones [7]. The biocenosis in question is pronounced peaked. Such biocenosis are easily destroyed with changing conditions of their life.
In trophic structure sestonophages are dominant (Table 2) The organisms collecting detritus from the ground surface as well as carnivora had high species richness. But as to their abundance and biomass, they were rather inferior to sestenophages. The rest of the throphic groups were weakly developed and were presented only in upper part of the biocenosis.
Table. 2. Throphic structure of M. phaseolinus biocenosis
Throphic groupings
Portion (in %) in
Species richness
Abundance
Biomass
Sestonophages
37
97,76
98,02
Collecting detritus from the bottom surface
28
1,64
1,04
Omnivorous eaters of the upper layer of bottom
2
0,14
0,30
Omnivorous eaters of the stratum of bottom
5
0,08
0,04
Carnivore
21
0,34
0,47
Phytophagues
2
0,01
0,01
Polyphagues
5
0,03
0,12
Due to the bottom trawling and soil dumping the investigated biocenosis was stressed by strong antropogenic silting in late eighties. As a result of it the area of biocenosis was decreased 2.3 times, compressing annually on the average 18%. In 1990 the share of biocenosis made up only 16% of the investigated area (Fig. 3).
Fig. 3. Dynamics M. phaseolinus biocenosis area.
The biocenosis preserved at silted parts of bottom was marked by very poor species richness. There were only 5 species of animals (M. phaseolinus, M. euprocta, N. latericeus, P. solitarius, T. stroemi). The animal benthos abundance was 15 times, biomass 1.6 times lower, than on the phaseolinum silt. The share of the dominant species decreased till 81% of abundance and 88% of zoobenthos biomass (Table 3).
Table 3. The level of the development of M. phaseolinus biocenosis at the different grounds
Type of ground
Number
of types
An average abundance sp./м2
An average biomass g/m2
Index stability (%) by
Dominant species
Abundance
Bio-mass
Portionя (%) by
Index of dominance
Abundance
Bio-mass
Phaseoline silt
45
1256± 91
135±12
37
23
97
89
0,91
Silt
5
84± 4
1± 2
93
80
81
88
0,99
The growing index of stability is connected with simplification of the biocenosis.
While further silting M. phaseolinus biocenosis is transforming into T.stroemi biocenosis.
References
1. Key to the Black - Athov Seas fauna. – Kiev: Naukova dumka, 1968, 1969, 1972. Т. 1, 2, 3. – 437 p., - 536 p., - 340 p.
2. Balogh J. Lebensgemeinschaften der Landtiere. - Berlin, 1958. – 560 s.
3. Bodenheimer F.S. Precis d,ecologie animal. - Paris, 1955. – 315 p.
4. Bykov B.A. Ecological dictionary. - Alma-Ata: Nauka, 1983. - 215 P.
5. Kiseljova M.I. The structure of Modiola phaseolina bottom biocenosis at the southern coast of the Crimea. Macrobenthos//Sea biology № 32. - Kiev: Naukova dumka, 1974. - P. 87-110.
6. Kiseljova M.I. Benthos of soft soils of the Black Sea. - Kiev: Naukova dumka, 1981. – 165 p.
7. Shorygin A.A. About biocenosis//Bull. of MOIP, Т.60, №. 6. – М., 1955. – P. 87-98.
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