Diatom diversity and ecological variables in the Arctic lakes of the Kostyanoi Nos Cape (Nenetsky Natural Reserve, Russian North)

We identified 185 diatom species in 87 samples collected from 17 Arctic lakes of the Kostyanoi Nos Cape in July 2003. Species richness varies from 9 to 97 per lake with Aulacoseira islandica (O.F. Müller) Simonsen, Fragilariamesolepta Rabenhorst, Psammothidium subatomoides (Hustedt) L. Bukhtiyarova and Round as dominant species. Bioindication attests to preponderance of temperate, moderately oxygenated, low-to-moderate organic-enriched alkaline, and circumneutral low saline water. Oligotrophic to mesotrophic state correlates with the type of sediments and low organic pollution (saprobity index 0.81-1.73 and Classes 2-3 of water quality). The diatom assemblages contain cosmopolitan species accompanied by the large group of 45 boreal species including 28 Arctic-alpine taxa. Canonical correspondence analysis shows conductivity and the type of sediments being the most important variables. Multivariate regression testifies to importance of depth and area of the lake. The community level analysis reveals four groups correlated with species richness, type of sediments, pH, and salinity. Potential species richness is estimated as 800 species square kilometer based on species-area relationships. Since the diatom assemblages of Arctic lakes are sensitive to climate warming and associated changes of salinity and trophic conditions, they are under high risk of extinction, the diversity losses being scarcely compensated by the rise of tolerant species.