Distribution of Different Groups of Zooplankton in Different Depths in the Southern Caspian Sea

This study was carried out on the community variations of zooplankton in different depths (5-100m) at 8 stations in 2008. Samples were collected through a zooplankton net (100 μm mesh) by R/V Gilan vessel. The most abundant zooplankton and its biomass were in depth of 5m in all seasons، but abundance decreased from coastal area towards deeper area as 74% (Spring and Summer)، 57% (Autumn) and 70% (Winter) of zooplankton community were in depths of 5 and 10m. The Copepoda constituted the main community in different depths and seasons during the year. This group was distributed with the abundance of 164 ind/m3 in depth of 100m in spring to 11289 ind/m3 in depth of 5m in summer during the year. The Rotatoria community increased in winter and it formed 48% of zooplankton abundance and 74% of its biomass. Its abundance decreased in spring and summer، but it increased during fall again.