The Results of Studying Diapausing Eggs (Cysts) of Brine Shrimp (Artemia) on the Bottom of Hypersaline Lakes of Altai Krai.

The results of 2020 studies of bottom cysts of brine shrimp Artemia in Lake Kuchukskoe and Lake Bolshoe Yarovoe in Altai krai (Russia) are presented. Artemia cysts were observed year round at the bottom of both lakes. The number of cysts depended on the type of bottom sediment. The biomass of bottom cysts in Lake Kuchukskoe was 154.2 t in spring, of which available and visually intact cysts constituted from 11.8 to 25.2 t. Bottom cysts of Artemia were not available for 27% of the lake area in Lake Kuchukskoe due to the high salinity of the water and salt precipitation. The viability of cysts from shallow bottom areas was 8.9% in spring. In Lake Kuchukskoe, cysts from accumulations on the coast, washed away by the runoff of melt water, played the main role in the formation of first generation of Artemia in spring. The deep water of Lake Bolshoe Yarovoe predetermined the peculiarities of the temperature regime in spring, which prevented brine shrimp cysts from ascending from the bottom if the depth exceeded 7.0 m. Significant silt deposits at the bottom of the lake were an aggressive environment for cysts, as was followed by the presence of different groups of cyst quality: visually intact, with defective chorion, gray or black. The biomass of bottom cysts in Lake Bolshoe Yarovoe was 38 934 t in autumn 2020, which exceeded the reproductive capacity of the Artemia population per year. This testified to the long-term period of accumulations of cysts at the bottom and their partly participation in the formation of the Artemia first generation in spring. In spring, the maximum hatching rate of nauplii from bottom cysts was 16% from depths exceeding 9.0 m and 26%, from a depth of 8.0 m. The viability of bottom cysts from Lake Bolshoe Yarovoe does not exceed 15% at the average; unhatched floating cysts settle back to the bottom in summer. [ABSTRACT FROM AUTHOR]