Solar and Wastewater Effects on Zooplankton Communities of the Imandra Lake (Kola Peninsula, Russia), 1990 to 2003

Both heliophysical and anthropogenic (wastewater) effects on zooplankton biomass and abundance of the Imandra Lake (the largest subarctic lake at Kola Peninsula, Russia) were investigated during the 1990 - 2003 period. We used different indexes of solar activity (sunspot numbers and UV- radiation values) as heliophysical factors. Information about UV- radiation values was derived from satellite data. As a parameter of anthropogenic pollution we used the information about wastewaters input in Imandra Lake by copper-nickel (Severonikel plant) enterprise and apatite-nepheline industry (AO Apatit). Besides we used the direct measurements of concentrations of the most important pollutants (Al, Ni, Cu) and biogenic components (N and P)in the Imandra Lake. It was shown that the correlation between heliophysical factors and zooplankton biomass and abundance was high and significant (r= 0.7- 0.8), and it was not significant between waste waters input volume and zooplankton productivity. According to the results obtained the main factor influencing zooplankton bioproductivity is solar UV-B radiation due to its damage effects. In addition for middle latitude Krasnoye Lake (Karelia, Russia; 1964 to 1984) and Lake Michigan (USA, 1984 to 1990) data we found nearly the same effect- anti-correlation between UV radiation level and zooplankton bioproductivity, but unfortunately the significance level was not sufficient. However, the effect at middle latitudes was some lower than at high-latitude Imandra Lake. Such discrepancy seemed to be associated with different day duration at high and middle latitudes. Our results seem to prove that solar forcing (mainly UV-B radiation) is significant factor governing zooplankton bioproductivity in subarctic lakes even in such polluted one like Imandra Lake.