Distribution of Mnemiopsis leidyi and Zooplankton in the South-western Caspian Sea, 2008

摘要

The study was conducted from January 2008 to December 2008, focused on spatial and temporal distribution of Mnemiopsis leidyi and zooplankton populations in the south-western area of the Caspian Sea. In summer and winter M. leidyi abundance and biomass values were between 1900 ± 1400 ind/m~2 , 110 ± 220 ind/m~2 and 370 ± 250 g/m~2, 1.0 ± 1.3 g/m2~ , respectively. The most individuals of a ctenophore (about 90%) were < 5 mm in length. A total of 19 zooplankton species were identified. Among them seven species were merozooplankton and 12 species were holozooplankton. The annual mean zooplankton abundance was recorded 5300 ± 1400 ind/m~3 which were lower than the previous years. The mass occurrence of M. leidyi appears to be one of the most important factors that reduce the zooplankton species and abundance, hence degrade the Caspian Sea natural ecosystem.