Reconstruction of ecosystems of Arctic lakes revealed

US, WASHINGTON (ORDO NEWS) — The studies were carried out in accordance with a state order by the V. Vernadsky Institute of Geochemistry and Analytical Chemistry of the Russian Academy of Sciences and the Institute of Water Problems of the Russian Academy of Sciences with the support of grants from the Russian Foundation for Basic Research.

Bottom sediments were selected by the Tsogu employees within the framework of the megagrant “Formation of water quality under the changing environment and climate of Western Siberia”. The work of scientists is published in the peer-reviewed journal Geochemistry. Studies have shown that sedimentation rates in the Arctic sector of Western Siberia range from 1.7 to 2.0 mm per year.

Concentrations of chemical elements along the entire length of the columns remain at the background level in both lakes . Only mercury showed a significant excess of the local background in the surface layers of bottom sediments. According to scientists, a possible reason is the intake of this substance from the atmosphere due to long-range transport with air currents.

“The vulnerability of the nature of the Arctic regions leads to a high reactivity of ecosystems. This determines an informative “record” of changes in the thickness of bottom sediments, including changes in biogeochemical cycles and global flows of pollutants in the atmosphere, as well as climate dynamics and ecosystem conditions. They are recorded on the basis of the geochemical composition and the remains of microscopic unicellular organisms in bottom sediments, ”said Vitaly Khoroshavin, director of the Institute of Earth Sciences at Tyumen State University.

Studies have shown that the characteristics of the sediment, which in both cases is clearly divided into two layers – loam in the upper part of the columns and sand at the base, do not significantly affect the distribution of elements in the columns.

As explained by Vitaly Khoroshavin, bottom sediments contain an extremely low percentage of organic matter even in the upper loamy parts of the columns. The enrichment factors calculated relative to the average contents in shales do not exceed two even for maximum concentrations in the selected samples, which allows us to consider the lakes examined as background, i.e. the ecological and geochemical features of these reservoirs are regulated mainly by natural processes.

A comparison of the data of diatom and particle size analysis (i.e., determining the size and quantitative ratio of particles composing loose rock) revealed the processes of restructuring of lake ecosystems, which is characterized by a significant change in the ratio of sand, clay and clay fractions in the bottom sediment. This may be due to the shallowing of water bodies as a result of climatic changes, the drying up of the climate of the Arctic, which lasted the last several thousand years.

To reconstruct the latest climatic changes in the Arctic regions, they plan to continue research using a combination of bioindication methods based on diatom analysis and geochemical determinations. Despite certain differences between the lakes, they are very close in chemical composition and element concentrations, which are within the normal range and below it. Both reservoirs are characterized by an increase in concentrations from the lower layers to the surface for almost all elements (more clearly manifested in Lake Langtibeito).

The north of Western Siberia is a region of intensive development of hydrocarbon deposits. There are more than 200 fields here, where 290-310 million tons of oil and 35-40 billion cubic meters of natural gas are produced annually. Intensive development of large gas condensate fields, construction of gas pipelines leads to an increase in anthropogenic pressure on the environment.

Therefore, it is important not only to reconstruct the dynamics of what is happening in the environment and climate in the Arctic regions of Western Siberia, but also to assess the dynamics of sedimentation of elements and the state of ecosystems in a long-term section, and to identify a possible anthropogenic contribution to these changes during the period of industrial development of oil and gas fields.

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