Evaluation of Possible Causes of Non-Predatory Mortality of Crustacean Zooplankton in a Small Siberian Reservoir

Abstract

Non-predatory specific mortality (NPSM) of dominant zooplankton species, Daphnia (longispina group) and Cyclops vicinus, was estimated during 1997-2000 sampling seasons on the basis of a new direct method: live/dead sorting and sediment trap measurements. Simultaneously measured ecological factors, such as water temperature, pH, dissolved oxygen, biomass of cyanobacteria, diatoms, greens and euglens, levels of polyunsaturated fatty acids of ω3 family, α-linolenic (ALA) and eicosapentaenoic (EPA), were considered as possible causes of the mortality using multivariant canonical correlation analysis. Toxicity was discarded on the basis of another set of study of the reservoir. As found, the best predictor of Daphnia mortality was EPA level, negatively correlated with NPSM value. Nevertheless, large part of variance of Daphnia mortality and practically all variance of Cyclops NPSM remain unexplained and need future investigation.