The distribution of biogenic elements in the vertical section of bottom sediments of Lake Kotokel (Eastern Baikal region)

Chemical composition of organic-mineral sediments (sapropel) of Lake Kotokel (Eastern Baikal region) based on 14.5 m and 16.5 m long drilling cores and distribution of the major biogenic elements (TOC, H, TN, S) and TP along the depth of bottom sediments have been studied. . A reduction type of diagenesis has been established, during which destruction of organic matter occurs. The major role in diagenetic transformations of organic matter belongs to different physiological groups of microorganisms, primarily heterotrophic, ammonifying and sulfate-reducing bacteria. The lightening of the isotopic composition of carbon confirms active microbial processes that change the initial composition of organic matter as a result of its anaerobic decomposition. The weighting of the TN isotopic composition in the upper sediment intervals indicates a rather intense nitrogen cycle and its ‘high’ loss from organic matter composition, which leads to the growth of δ15N.