Peculiarities of development of macrozoobenthos communities under influence of Dreissena polymorpha Pall in experimental mezocosms

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/m(2)) and without it. The investigations were carried out i n period from 30 May to 5 September 1994 in Sample trays (16 m(2)) near Ryb inskoe storage pond. The level of faunistic similarity of macrozoobenthos c ommunities of studied mezocosms was 67%. Chironomidae dominates by the numb er of taxa, following species were constantly observed: Lymnaeae ovata, L. stagnalis, Valvata depressa, Euglesa obtusalis, Chironomus annularius; Poly pedilum bicrenatum, Tanytersus gr. holochlorus, Cladopelma viridula, Glypto tendipes glaucus; Uncinais uncinata, Batracobdella palludosa. The influence of D. polymorpha causes the increase in species variability of communities , the strengthining the role of detritovores and predators, increase in num ber, biomass and productivity of benthos communities, inhibition of other f iltrate molluscs. The influence of D. polymorpha on benthoic organisms is r elated to their feeding strategy. Dreissena stimulates the development of d etritovores enriching substrate by organic substances and depressed the dev elopment of filtrators competing with them for food.