Trophic relations in plankton communities in the Black Sea before and after Mnemiopsis leidyi (A. Agassiz) invasion

Long-term data on phytoplankton biomass dynamics, on numbers of pelagic fish, their stocks and catches were used. Data from YugNIRO plankton surveys for the period from 1959 to 1993 were also used. Phytoplankton biomass has increased over the period under study. Regression analysis has revealed a downward trend in annual average biomass of prey zooplankton in the northwestern Black Sea. In this area 13-year fluctuation cycle in biomass was observed. In the eastern Black Sea, there are 7-year periods of phytoplankton biomass fluctuations. From the late 1970s to the early 1980s there was a considerable growth in jellyfish Aurelia aurita population in the Black Sea. Later on its biomass was on a steady downward trend in all parts of the sea and had decreased twentyfold to the level of 4-5 million tons by the time the invader (ctenophore Mnemiopsis leidyi) was able to swamp pelagial of the Black Sea. It remained at that level during all the subsequent period of coexistence of the two Coelenterate species. During the 1989-1991, M. leidyi biomass was at a level of 30-40 million t, decreasing to 18.9 million t in 1992. Pelagic fishes (bluefish Pomatomus saltatrix, horse mackerel Trachurus mediterraneus and the bonito Sarda sarda) had almost disappeared from the pelagic Black Sea by 1966. Two contrary tendencies in abundance of short-cycle species, the anchovy Engraulis encrasicolus and the sprat Sprattus sprattus phalericus was observed.

Bibliographic Details

Main Authors:	Grishin, A.N., Kovalenko, L.A., Sorokolit, L.K.
Other Authors:	Yakovlev, V.N.
Format:	Journal Contribution biblioteca
Language:	Russian
Published:	1994
Subjects:	Mnemiopsis leidyi, Phytoplankton, Abundance, Pelagic fish, Marine ecosystems, Seasonal variations, Sarda sarda, Engraulis encrasicolus, Sprattus sprattus phalericus, Ctenophores, Численность, Черноморская хамса, Гребневик, Трофические группы, Биомасса,
Online Access:	http://hdl.handle.net/1834/15787
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