Dynamics of Vegetation Cover of Cryolithozone Water Bodies due to Climate Change and Flow Regulation on the Example of the Lower Kolyma Valley

The analysis of materials of researches conducted by E.R. Trufanova in 1966–1969 on aquatic vascular plants of water bodies of the lower reaches of the Kolyma River, original data collected in 2015 and 2020, and multi-temporal satellite images showed a number of changes in the vegetation cover of water bodies. Seven species previously reported for the studied lakes were not found and 10 taxa not recorded or not recognized were found. A scheme for identification the successional stage of water bodies is proposed. Most of the studied water bodies are in the "old" stage. The greatest diversity of aquatic plants is characteristic for the stage "mature lakes" and "old lakes with a single water area". The example of Zhirkovo 1 Lake showed that for >50 years it has remained at the same stage of development, but the species composition has changed significantly (K1 = 0.41). While maintaining the current trends of climate change (increase in average annual temperature and precipitation), the studied water bodies will continue unidirectional aging and overgrowing, which will be accompanied by a decrease in depths and a gradual decrease in species diversity of aquatic plants. The old lakes of low and middle floodplain level can be in a state of dynamic equilibrium for a longer period of time and maintain high diversity of aquatic vascular plants due to periodic flushing by flood waters, while their drainage will occur more frequently.