Biocenosis Of Intruders Mya Arenaria And Cunearca Cornea (scapharca) In The North-western Azov Sea
BIOCENOSIS OF INTRUDERS MYA ARENARIA and CUNEARCA CORNEA (SCAPHARCA) IN THE NORTH-WESTERN AZOV SEA
A.S. Terentijev, N.M. Litvinenko
Southern Scientific Research Institute of Marine Fisheries
and Oceanography (YugNIRO), Kerch, Ukraine
At the end of 60-ths bivalve mollusk Mya arenaria [1] have gone into the Azov Sea, and in 1989 another bivalve mollusk Сunearca cornea [2] was found there. For the first time this species was found in the Black Sea in 1983 at Bulgarian shelf [3].
From that time those species have been widely distributed around tha Azov Sea. Both species were distributed independently. Insignificant negative value of Coal’s coefficient of association (-0,12) was probably connected with more close С. cornea dependence on ground composition (Table 1).
Table 1. Optimum ground composition for M. arenaria и C. cornea
Species
Dependence on ground composition %
Ground composition, %
Shells
Sand
Silt
M. arenaria
19
23
13
64
C. cornea
53
5
17
78
The Table shows that С. cornea prefers more silted grounds and avoids shells.
At the present time these species formed independent biocenoses. Mya boicenosis was formed in the northern part of the sea and along Arabatskaya Strelka while Cunearca biocenosis turned out to be concentrated near the Azov coast of Kerch Peninsula. Approximately similar amount of both animal species belonged to both biocenoses and the largest number of species fell on bivalve mollusks (Table 2).
Besides the dominant species there were polychaetes Nephthys hombergii and Nereis succinea, bivalve mollusk Cerastoderma glaucum, additional mollusks Abra ovata, Hydrobia acuta, crustaceans Balanus
Table 2. Species variety of Mya и Cunearca biocenoses
Biocenosis
Mya
Cunearca
Species number
Rate, %
Species number
Rate, %
Bivalvia
5
36
5
42
Gastropoda
1
7
1
8
Polychaeta
4
29
4
33
Crustacea
3
21
2
17
Coelenterata
1
7
0
0
Total
14
100
12
100
improvisus and Rhithropanopeus harrisi tridentata constant in the composition of Mya biocenosis. The latter is an intruder in the Azov Sea. Mollusks Cerastoderma clodiense, Mytilaster lineatus, polychaetes Nereis diversicolor and Nephthys cirrosa, amphipoda Ampelisca diadema and actinia Actinothoe clavata. 12 species were in the composition of Cunearca biocenosis. N. hombergii, N. succinea, A. Ovata were constant. C. glaucum, H. acuta, B. improvisus and R. harrisi tridentata were additional. C. clodiense, M. arenaria, N. cirrosa, Nereis zonata were rare. Both biocenoses were alike according to their species composition (Chekanovsky-Serens coefficient of similarity was 0,77). But Shorygin coefficient of similarity (0,67) based on specific abundance shows that in spite of close species composition of biocenoses in question the species belonging to it have different importance. In the first biocenosis C. Glaucum plays rather important role, and in the second one it is A. ovata. Those species do not only often occur in the above biocenoses but the even have the largest biomass among all the species that are not dominant.
Species composition of the biocenoses in question is characteristic for traditional for Azov Sea biocenoses Abra и Cerastoderma [5] of which they have evidently originated.
The biocenoses investigated have almost similar zoobenthos biomass, but its abundance in Cunearca biocenosis is 2.4 times higher than in Mya biocenosis (Table 3).
The role of the dominant species in Mya biocenosis turned out to be higher than in Cunearca biocenoses. Comparing dominance index of the leading species and dominance index of the leading species from initial biocenoses we get the result that Abra dominance index in Mya biocenosis is 53 times lower, аnd Cerastoderma is 37 times lower than the dominant species has, and in Cunearca biocenosis those values are 22 и 42 times respectively. Cerastoderma biocenosis was evidently of great importance in formation of Mya biocenosis, and biocenosis Abra played an important role in formation of biocenosis Cunearca.
Table 3. Average indices of the development level of Mya and Cunearca biocenoses
Biocenosis
Abun-dance pieces/м2
Biomass g/м2
Dominant rate, %
Dominance index of the leading species [4]
due to abundance
Due to biomass
Mya
369± 66
590±200
23
94
0,91
Cunearca
880±290
597± 97
22
86
0,84
References
1. Nekrasova M.Ya., Khrustalev Yu.P. Influence of oceanological and anthropogeneous factors on biological potential of the Azov Sea bottom fauna /Rational utilization and preservation of natural resources of the basins of the Black and Azov Seas. - Rostov-on-Don: Publ. of Rostov SU, 1988. - P. 59-67.
2. Chikhachev А.S., Frolenko L.N., Rekov Yu.I. Bivalve Anadara sp. is a new intruder into the Azov Sea //Coll. Main problems of fishery and preservation of fishing reservoirs of the Azov basin. - Rostov-on-Don: Poligraph, 1996. - P. 165-167.
3. Tsvetkov L.P., Marinov T.М. Fauna recruitment of the Black Sea and changes of its bottom ecosystems //Hydrobiology. В. 27. - Sofia, 1986. - P. 3-20.
4. Bykov B.А. Ecological Dictionary. - Аlma-Аtа: Nauka, 1983. – 215 P.
5. Vorobyev V.P. Benthos of the Azov Sea. – Simferopol: Krymizdat, 1949. – 195p.
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