Macroinvertebrates of fluctuating lakes in Mongolia

The dynamics of the water budget of Orog Nuur and Taatsiin Tsagaan Nuur fluctuating lakes in the Valley of the Lakes (Wes­ tern Mongolia) in the period 2010–2018 is studied. It is shown that Orog Nuur Lake has passed to the wet phase in its long­term cyc­ le, while Taatsiin Tsagaan Nuur Lake is currently in a transitional phase, which in previous cycles lasted 2–4 years. The composi­ tion and long­term changes in the species composition and quan­ titative characteristics of macrozoobenthos and macrozooophytos of Orog Nuur Lake, and macrozoobenthos and nekton of Taat­ siin Tsagaan Nuur Lake is studied. A total of 27 species of mac­ roinvertebrates is recorded for Orog Nuur Lake and 23 species for Taatsiin Tsagaan Nuur Lake. During the study period, Orog Nuur Lake showed an increase in the diversity and abundance of benthic communities that exhibit multi­annual fluctuations due to changes in water level. The macroinvertebrate communities of Taatsiin Tsagaan Nuur Lake are typical of a temporary water body, in each year of research, being dependent on the area of the lake and water budget, which in turn depends on changing patterns of its filling. Based on data from 2014, when Taatsiin Tsagaan Nuur Lake was first filled with water after a dry phase, we calculated sex ratios and average individual body mass for each sex group of three syntopic species of Spinicaudata that experienced a sharp increase in abundance.