Role of Unionidae and Sphaeriidae (Mollusca, Bivalvia) in the Eutrophic Lake Zbęchy and its Outflow

The abundance, biomass, respiration, and filtration rate of the Unionidae and Sphaeriidae and their significance to the phosphorus cycle was estimated in an eutrophic lake in Poland, situated in an agricultural area, and in its outflow canal. A decrease in Unionidae biomass was compensated for the Sphaeriidae in terms of both biomass and filtration rate. Depending on the developmental state of the Unionidae and Sphaeriidae populations, the volume of pumped water, the amount of removed and assimilated seston and the phosphorus excretion changed significantly.