Benthic macroinvertebrates and aquatic mosses in pristine streams of the Tolvajärvi region, Russian Karelia

As a preliminary stage in characterizing the biodiversity patterns of pristine stream habitats in Russian Karelia, the macroinvertebrate fauna and bryophyte flora were studied in three river systems of the Tolvajärvi area. The pristine watercourses of this area are among the few representative watercourses to be used as reference sites for the studies dealing with the impact of forestry on lotic biodiversity. The benthic fauna and flora of the area were found to include many species considered as endangered, rare or with a northern distribution in Finland. In Canonical Correspondence Analysis, the most important environmental variables affecting the distribution and abundance of the benthic fauna were the abundance of aquatic mosses, the amount of organic matter and woody debris, the size of the drainage area and the concentrations of nutrients and iron in the water. Filter feeding trichopteran and algae feeding chironomid larvae dominated the stable lake outlet habitats with abundant moss vegetation, while small streams with higher nutrient and iron concentrations and large amount of organic matter were dominated by shredding stonefly species of the generas Nemoura, Nemurella and Leuctra.