The role of gelatinous macroplankton, jellyfish aurelia, and ctenophores mnemiopsis and beroe in the planktonic communities of the Black Sea

On the basis of field and experimental studies in Golubaya Bay (near Gelend zhik) during the period from August 1999 to March 2000, the abundance, biom ass, ratio between body size and weight, as well as carbon content in wet b iomass were estimated for a newcomer into the Black Sea-the ctenophore Bero e ovata. On the basis of the material obtained and using the data on the ox ygen consumption rates, the specific metabolic rate, production rate, and t he food intake of beroe were estimated. We also estimated the influence of this ctenophore on other species of gelatinous macroplankton: the jellyfish aurelia and the ctenophore mnemiopsis. The above-listed ecological and phy siological parameters were compared; the differences between the ratio valu es of dry to wet weight for all three species were revealed to be insignifi cant (2.0-2.5%). The carbon content in the wet biomass was 0.1% for mnemiop sis, 0.15% for beroe, and 0.3% for jellyfishes. Due to a more intensive met abolism, growth, and greater feeding rates of the ctenophores, especially b eroe, as compared with the autochtonous species Aurelia (by factors of abou t 1.5 and 2, respectively), the populations of mnemiopsis (a competitor of aurelia and planktivorous fishes) significantly reduced the stocks of these fishes. In August-October 1999, a new intruder beroe appeared; during the period under study, it grazed on (according to a preliminary estimation) 30 -80% of the population of mnemiopsis. This resulted in a decrease in the bi omass of mnemiopsis by a factor of about 10 and an increase in the biomass of aurelia.