Composition and abundance of Zooplankton in kardzhaly reservoir

The zooplankton community structure in “Kardzhaly” reservoir (South-East Bulgaria) was studied from July2000 to November 2002. The seasonal cycles and population dynamics of the main taxonomic groups are describedand discussed. The zooplankton community was composed of 12 species of Rotifera, 13 species of Cladocera, 7species of Copepoda, 1 species of Ostracoda, 1 species of Cnidaria (Coelenterata), 1 species of Hydracarina and1 species of Ciliata. The abundance of the zooplankton increases, 5 times on average, between the limnetic andthe riverine zone of the reservoir. The Copepoda dominated the limnetic zone, closely followed by Cladocera,while in the transitional and the riverine zones the opposite was true. The zooplankton community was mostlycrustacean, with the following perennial species: Kellicottia longispina and Keratella cochlearis from the Rotifera;Daphnia longispina, Bosmina longirostris and Bosmina coregoni from the Cladocera, as well as Cyclopsvicinus, Eudiaptomus gracilis and the nauplii and copepodites of the Copepoda. Some relationships were foundbetween the trophic state, the reservoir exploitation and the zooplankton community.