Influence of environmental mineral composition on the indices of water-salt metabolism in Dreissena polymorpha Pallas introduced to Rybinsk Reservoir

Abstract

Threshold levels of sodium, potassium, calcium, and magnesium defining the distribution range of Dreissena polymorpha in fresh water are 0.07, 0.0015, 0.3, and 0.01 mmol/l, respectively. Reduction of water mineralization decreases concentrations of sodium, potassium, and magnesium in the hemolymph and soft tissues and increases calcium concentration in hemolymph. Introduction of zebra mussel into freshwater reservoirs is limited by the calcium concentration in the water. The upper limiting levels of sodium, potassium, calcium, and magnesium in the environment which define the range margins in D. polymorpha in brackish water are 22, 0.9, 6.4, and 2.7 mmol/l, respectively. Under such conditions, both the content of sodium in the hemolymph and muscles and the content of potassium and magnesium in the hemolymph increase in zebra mussel. In comparison to aboriginal species, D. polymorpha is more sensitive to the environmental potassium concentration. Hyponatraemia and hypercalcaemia in bivalves under stress conditions may become a characteristic in assessing the effect of adverse environmental factors. The freshwater origin of zebra mussel in the Rybinsk Reservoir is discussed in regard to the data obtained. The problem requires special studies.