Peculiarities of the Species Composition, Abundance, and Biotope Distribution of Mollusks of the Family Sphaeriidae in Rivers with Many Lakes in the Catchment Area (Using the Example of Water Courses of the Onega Lake Basin)

Abstract

Using the example of rivers in the Onega Lake basin, the species composition of mollusks of the Sphaeriidae family and their abundance, biomass, and contribution to benthic communities in rivers with many lakes in the catchment areas have been analyzed. Patterns of the spatial distribution of species across biotopes and gradients of environmental variables are traced. Twenty-six species of mollusks of this family are identified, with European–Siberian species predominating. Most species of mollusks of the family Sphaeriidae found by us have wide ecological ranges and are found in water bodies of various types. It is found that the contribution of Sphaeriidae to the species richness and functioning of aquatic communities in rivers in the conditions of branched lake–river systems (Lake Onega basin) exceeds the values usual for rivers with a small number of lakes in the catchment area. Using the ANOSIM and PERMANOVA methods, it is proven that the species composition of rocky rapids and riffles, sandy rifts, and soft bottom soils is different. Using the IndVal test, seven species are shown to have a statistically significant association with one of these biotopes, and four of them have a statistically significant association with the rocky bottoms of river rapids and riffles. Using the NMDS method, it is shown that the greatest changes in the species composition of representatives of Sphaeriidae are observed when environmental conditions change from small streams with a slow current and brown water to large rivers with a fast current and clear water.