Emergence of Midges (Chironomidae, Diptera) from a Saline Lake as a Source of Organic Matter and Essential Biochemical Compounds for Arid Ecosystems in South Siberia

Midges (Chironomidae, Diptera) are dominant amphibiotic insects in zoobenthos of the large saline Lake Shira located in the arid landscape of South Siberia. During two vegetation seasons we measured the dynamics of chironomid emergence from littoral parts of four stations in the lake. During one of the vegetation seasons we also measured chironomid emergence from profundal parts (depth of 6 m) of the same stations using original floating traps. Both seasonal dynamics and daily means of emergence values significantly varied among the studied stations and depths and were related to the bottom sediment type. The annual export of wet biomass (calculated as the sum of daily values for a vegetation season) was equal to 0.61 g per square meter of water surface and included proportional contributions of the areas with various bottom sediment types. Based on the values of benthic secondary production, we estimated additional annual export of chironomid biomass from the profundal part of the lake of approximately 1 g of wet weight · m−2. Besides, the total export of polyunsaturated fatty acids (PUFA) calculated using the previous data on PUFA content in the studied chironomid taxa (~ 2 mg · m−2 year−1) appeared to be one of the lowest when compared to estimations for chironomids and some other amphibiotic taxa from similar steppe landscapes