Vol 280

The study is devoted to the quantitative assessment of organic carbon (C_org) deposition rates in the bottom sediments of small lakes located in the south of Western Siberia. The studied water bodies cover a wide range of landscape-climatic conditions and types of sedimentation environments. Despite their local dimensions, the small lakes of the region demonstrate exceptionally high efficiency of long-term carbon burial. It is shown that their capacity to accumulate C_org is comparable to or even exceeds that of such recognized carbon depots as bogs and marine shelves. The work is based on a comprehensive analysis of bottom sediments, including radiometric dating (Pb-210, Cs-137) to determine sedimentation rates and layer ages, as well as morphological, elemental (CHNS analysis), and X-ray diffraction analyses. According to the obtained data, the average C_org deposition rate in the studied lakes reaches 462±29 g/m² per year. It has been established that the majority of carbon (> 50 % in most cases) accumulates specifically in the form of organic matter, even in lakes with intensive intra-basin (authigenic) carbonate formation. The study revealed the main factors controlling carbon accumulation: productivity of aquatic communities (phytoplankton, zooplankton, macrophytes), total sedimentation rate, sediment ash content (mineral fraction proportion), and local morphometric features of the lakes (depth, basin shape). The absence of a clear dependence of carbon deposition rates on landscape zonality underscores the critical importance of considering local conditions when modeling the contribution of small lakes to the global carbon cycle. The obtained results substantially fill gaps in regional carbon assessment and prove the significance of small lakes in the south of Western Siberia as highly efficient and stable natural depots of organic carbon under conditions of continental sedimentation.