The paper presents results of studying the diagenetic transformation of bottom sediments from two freshwater lakes — Talatinskoe and Tundrovoe — in the Vaigach Island. The study of biogeochemical processes in the conditions of present-day climate instability is especially important for Arctic water ecosystems, since their environmental sustainability is extremely low, and the effects of global warming are most significant. According to available climate forecasts, the Vaigach Island is located in the zone of maximum changes in natural complexes. The lake-river systems of the island are unique island geosystems, but to date they are poorly understood.

Our aim was to carry out comprehensive research on the biogeochemical processes of the sulfur cycle as the geochemical aspect of the bacterial sulfate reduction process, which involves the conjugation of the cycles of carbon, sulfur and iron, participating in redox processes that play an important role in sedimentation and early diagenesis. In order to achieve this goal, a multi-method (hydrochemical, geochemical, etc.) approach was developed using standard generally approved laboratory practices adapted to the study goals.

Based on the pollen data, it was found that the formation of the bottom sediments of Lake Talatinskoe occurred in the current climatic conditions of the tundra. The data on the distribution of grain size fractions allow us to conclude that the sediment sequences of both lakes undergo regular destruction and mixing during seasonal freezing-thawing. This was reflected in the random distribution of all the parameters studied and in the impossibility of determining the sedimentation rate. The data obtained on the quantitative characteristics of sulfate reduction parameters (reduced compounds, forms of reactive iron, the amount of organic matter and its qualitative composition), their distribution and transformation indicate a low intensity of redox processes in precipitation. The most likely reason for this is the high degree of humification of the terrigenous organic matter and the low temperatures of the microorganisms’ habitat.