Causes of Technogenic Changes in a Freshwater Zooplanktonic Community

The situation in water bodies of northwestern Karelia in 1992–2001 was analyzed. As a result of waste discharge from the mining and ore-processing works, weakly mineralized hydrocarbonate-calcium waters changed into highly mineralized waters with the prevalence of potassium ions and sulfates. The total abundance and biomass of zooplanktonic communities decreased. Using the methods of principal components and partial correlations, differences in the responses of zooplankters to mineral pollution were revealed. Typical inhabitants of northern water bodies decreased in numbers, and the species Eudiaptomus gracilis Sars and Heterocope appendiculata Sars (Calanoida) disappeared. On the other hand, eurybiontic species prevailing in water bodies with higher mineralization manifested a positive reaction to the increase in the contents of dissolved mineral compounds. Toxicological experiments made it possible to estimate the survival threshold for E. gracilis and H. appendiculata: the populations of these crustaceans in the polluted water body perished when potassium concentration in water exceeded 50 mg/l.