FRESHWATER DIATOM ASSEMBLAGES FROM 23 LAKES LOCATED NEAR NORILSK, SIBERIA: A COMPARISON WITH ASSEMBLAGES FROM OTHER CIRCUMPOLAR TREELINE REGIONS

Abstract

Knowledge of the composition and ecological preferences of diatom assemblages in northern regions is important for paleoenvironmental reconstructions of variables related to climate and/or anthropogenic disturbances. Relatively little is presently known about diatoms from circumpolar treeline areas, especially for lakes located in northern Russia. Our study set included lakes in the Siberian tundra, forest-tundra, and boreal forest regions close to Norilsk, of which nine sites were subject to anthropogenic disturbances, such as mining and housing developments. We enumerated surficial sediment diatom assemblages and used multivariate statistical techniques to investigate which environmental variables were important in explaining the variation in diatom assemblages within our lake set. Deeper lakes were associated with higher abundances of planktonic centric taxa, such as Cyclotella Kützing species. Warmer, higher conductivity forested lakes were associated with higher abundances of planktonic pennate taxa, such as Fragilaria nanana Lange-Bertalot. Diatom assemblages in the colder tundra lakes were significantly different from those in forested regions, and were dominated by small benthic Fragilaria Lyngbye species. Disturbed lakes near the Norilsk smelters exhibited slightly higher metal (Cu) concentrations and conductivities, and were associated with pollution-tolerant Nitzschia Hassall taxa, as well as species associated with higher electrolyte concentrations, such as Navicula capitata Ehrenberg. However, in comparison with diatom assemblages from other regions of intense mining (e.g. Sudbury, Canada), the assemblages appear relatively unaffected by mining activities, most likely reflecting the suppression of aqueous metal concentrations due to the alkaline nature of these lakes. Overall, diatom assemblages were very similar to those found in northern Canadian and Fennoscandian lakes, suggesting mat the Siberian taxa are representative of a circumpolar arctic diatom flora.