Biogeochemical Features of Functioning of Small Arctic Lakes of the Khibiny Mountains under Climatic and Environmental Changes

Natural and anthropogenic factors affecting the composition of waters of the Arctic mountain lakes of the Khibiny alkaline massif were determined and the impact of global climatic and environmental changes on the functioning of primary producers, phytoplankton, was estimated. The geochemical, climatic, and morphometric features of the catchment area of the territory and basins, as well as anthropogenic load were characterized. It was established that the waters of the Khibiny lakes have hydrocarbonate–sodic composition, neutral and weakly acid pH values, low mineralization and concentrations of trace elements, and relatively elevated contents of K + cation. Based on the extremely low contents of nutrients and phytoplankton, the studied lakes are classed as oligotrophic. Metals mainly occur as ions due to the low content of organic matter. Phytoplankton represented by typical Arctic species is characterized by the poor species composition and low quantitative parameters. It was revealed that pH value, mineralization, content of major ions and trace elements, and quantitative parameters of phytoplankton decrease, whereas, the fraction of sulfate fraction in anion composition increases with increasing altitude of the lakes. The influence of atmospheric emissions from the adjacent Severonikel and JSK Apatit enterprises causes an increase of Cu, Ni, Zn, and Sr contents, as well as nitrogen compounds in lake waters. An increase of heavy metal content (Ni, Cu, Pb, Cd, Hg) in the surface layer of bottom sediments of mountain lakes reflects the anthropogenic impact from local productions and transboundary transport of contaminants in the high atmosphere layers. In addition to the accumulation of heavy metals, the bottom sediments show an increase of population and change of species diversity of diatoms, which likely reflects an increase of open-water period owing to the present-day climatic changes in Arctic.