Institute of Biology of Inland Waters, , Russian Academy of Science, Borok, Nekouzsky raion, , Yaroslavskaya obl. 152742, Russia

Abstract

To estimate the influence of Dreissena polymorpha as a biotic factor on the main groups of macrozoobenthos the author studies the structure of benthos communities in artificial strictly controlled ecosystems (mezocosms) with Dreissena (1 kg/m2) and without it. The investigations were carried out in period from 30 May to 5 September 1994 in sample trays (16m2) near Rybinskoe storage pond. The level of faunistic similarity of macrozoobenthos communities of studied mezocosms was 67%. Chironomidae dominates by the number of taxa, following species were constantly observed: Lymnaeae ovata, L. stagnalis, Valvata depressa, , Euglesa obtusalis, Chironomus annularius, Polypedilum bicrenatum, Tanytersus gr. holochlorus, Cladopelma viridula, Glyptotendipes glaucus, Uncinais uncinata, Batracobdella palludosa. The influence of D.polymorpha causes the increase in species variability of communities, hte strengthining the role of detritovores and predators, increase in number, biomass and productivity of benthos communities, inhibition of other filtrate molluscs. The influence of D.polymorpha on benthoic organisms is related to their feeding strategy. Dreissena stimulates the development of detritovores enriching substrate by organic substances and depressed the development of filtrators competing with them for food.