Effect of Zebra Mussel Dreissena polymorpha (Pallas, 1771) (Mollusca, Dreissenidae) and Perch Perca fluviatilis (L.) (Pisces, Perciidae) of Different Age Groups on the Structure and Main Characteristics of Macrozoobenthos in Experimental Mesocosms

Abstract

The composition of macrozoobenthos in experimental mesocosms has been studied. A total of 116 invertebrate taxa are found, with chironomids (50 species), mollusks (25), and oligochaetes (21) the most widely represented. Most of the revealed taxa (61%) are common for Dreissena polymorpha (Pallas, 1771) biocenoses in the Rybinsk Reservoir; other species have invaded mesocosms during the experiment. The minimal number of invaders is found in mesocosms with perch larvae; the maximal is in both variants with the zebra mussel. It is shown that in the absence of zebra mussels those age groups of perch consuming macrozoobenthos reduce its main structural characteristics. The maximum sum of the main structural characteristics is recorded in mesocosms with yearlings of perch and zebra mussels. This indicates a positive environment-forming role of Dreissena polymorpha in benthic communities and the possibility that other invertebrates can use its druses as refuge.