3 research outputs found

    Ctenophores-invaders and their role in the trophic dynamics of the planktonic community in the coastal regions off the Crimean coasts of the Black Sea (Sevastopol Bay)

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    The abundances, biomasses, and population structures of two introduced ctenophore species-Mnemiopsis leidyi and Beroe ovata-were monitored along with mesoplankton in the near-shore waters of the northern Black Sea (Sevastopol Bay and adjacent regions) over a period of four years (2000-2003), after the B. ovata invasion. The annual dynamics of the M. leidyi population were similar in these years: very low abundances and biomass values were observed during the major part of the year ( unlike previous years) with a short-term peak in the summer-early autumn. B. ovata development during the growth in the M. leidyi biomass resulted in a sharp fall in the M. leidyi biomass down to extremely low values. The interannual differences in the populations of both ctenophore species were reflected by their quantitative parameters: the maximum biomass of M. leidyi varied from 790 g/m(2) in 2001 to 211-266 g/m(2) in other years. The maximum biomass values of B. ovata (38.9 and 32.5 g/m(2)) were observed in 2001 and 2003, respectively. In 2000-2003, from July to September, during the peak in mnemiopsis development, the population consumed from 1.9 +/- 0.4 to 13.4 +/- 5.7% of the mesoplankton biomass per day, while in the years of B. ovata absence, these values were as high as 30-40%. For the first time, the grazing rate of microzooplankton by M. leidi larvae was estimated. In August 2003, the maximum daily consumption rate was as great as 23-25% of the microzooplankton biomass. The daily rations of the mnemiopsis larvae on microzooplankton were close or even higher than those on mesoplankton
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