Structure and heterogeneity of the Cladocera taphocoenoses in lakes of the Sredny Island (Keretsky archipelago, Kandalaksha bay of the White Sea)

Surface sediments, which were selected from various depths in three lakes of the Sredny Island (Karelia, Russia), were analyzed for subfossil Cladocera assemblages. In total at least 30 taxa remains were identified in samples of surface sediments. Predominance of cold-water littoral and cosmopolitan taxa was noted according to biotypic characteristic. Eurybiont Chydorus cf. sphaericus and typical of wetlands, the phytophilous Alonella nana , were most common in Cladocera taphocoenoses. Spatial heterogeneity was noted in subfossil Cladocera assemblages from various depths. Pelagic taxa proportion increased just as littoral taxa proportion decreased towards the center of lake. Several species remains were only found in littoral surface sediments samples.