INTERANNUAL CHANGES IN THE BIOMASS OF THE BLACK-SEA GELATINOUS ZOOPLANKTON

The 15 year changes in the total gelatinous biomass consist of a gener al trend to increase, from 250 g m(-2) in 1980 to 2500 g m(-2) in 1995 , and fluctuations with a period of similar to 4 years performed again st the background of this trend in the upper 150 m layer. Different sp ecies occupying distinct trophic niches form these peaks. When represe nted as the percentage of the total zooplankton biomass, Aurelia aurit a and Mnemiopsis leidyi exhibit the contra-phase fluctuations where a sharp increase in M. leidyi is accompanied by a decrease in the A.auri ta biomass.