Scientific Principles of Biomonitoring of Lake Onego

Original scientific approaches to the assessment of spatial and temporal variability of biota of Lake Onego, which may be used as a basis for its biomonitoring, are proposed for the first time. Reliably differing natural phenological phases of the seasonal cycle of plankton of Lake Onego have been revealed. The terms, duration, and interannual variability of phases are the criteria of reaction of the planktonic system to climatic changes. A series of models for assessment of the functioning stability of the ecosystem was developed on the basis of the regression method of minimization of orthogonal distances. Biotic indexes elaborated on the basis of the benthos structure were used for zoning of the bottom of Lake Onego. Three zones—of anthropogenic impact, intensive development of amphipods, and effect of geochemical anomalies—are specified. The proposed approaches may be applied in monitoring the status of large lakes in the boreal zone.