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The upper part of the subsurface component of the Earth's cryosphere—polygonal peatlands—are considered in this paper. The polygonal peatlands are widespread in the cryolithozone in northwestern Siberia. When the upper permafrost layer thaws under the influence of climatic fluctuations, the ice-bearing transition and intermediate layers in the polygonal peatlands serve as a buffer zone. Therefore, the identification of these layers is a crucial task. The specific features of the layers, their relationship with ice of various origins, and the properties of peat have been determined. The differences in the structure of the intermediate layer, associated with polygonal microrelief of the surface, have been revealed. Thawing of the transitional layer against the background of modern warming has been recorded on the basis of monitoring of a seasonally thawed layer. To identify the transitional and intermediate layers, the indicators—the cryogenic structure, degree of preservation, color, water content, and density of peat—have been determined. [ABSTRACT FROM AUTHOR]

The species composition and dominating complexes of fish in catches are considered. The fraction of mass fish species in catches is shown (for small rivers and the channel zone). The structural (size and age) and functional (fertility) parameters of some nonmigratory and invader fish species are characterized. Main biological parameters are considered in the time-space aspect over the widespread and numerous fish species. [ABSTRACT FROM AUTHOR]