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The Wadi El-Rayan is a depression in the Fayoum oasis collecting agricultural drainage water from the Fayoum. Since 1973, this drainage water formed two man-made lakes. Twenty years ago, a third lake, called Lake Magic was formed. Since this newly formed lake was not yet studied, in January of 2019 we conducted research related to its physico-chemical (ion composition, nutrients, heavy metals, etc.) and biological (phyto-, bacterio- and zooplankton) characteristics. The depth of the lake ranged from 1.5 to 9.0 m, water transparency was up to 4.0 m, and the water temperature was 13.6 °C. The average salinity was 29.1 g/l, and the salinity of drainage waters from agricultural fields was 2.9 g/l. A total of 28 phytoplankton species was identified belonging to Bacillariophyceae (eight species), Dinophyceae (three species), Cyanobacteria (seven species), Chlorophyceae (nine species) and Conjugatophyceae (one species). Chlorophyll a content varied from 14.3 to 24.2 μg/l. In zooplankton, there were three species of Ciliophora, five of Rotifera, and two Copepoda as well as Nematoda and Cirripedia larvae. Salinity in Lake Magic was much higher than in drainage waters coming in the lake. This is a result of a strong salinity increase in Lake Magic after its creation due to climate aridity, and salinity may markedly increase during the next 20 years along with the sharp changes of the lake's ecosystem.

Salinity is one of the most important factors in aquatic ecosystems, but its filtering role in the Diptera community species composition is still poorly studied. This issue was studied in the diverse Crimean water bodies. A total of 425 samples were collected from freshwater to hypersaline waters. In 73% of the 425 samples examined, representatives of Diptera were found; their larvae and pupae belonged to seven families. Сhironomid species composition was analyzed in 47 samples. The most common were Chironomidae, which were in 94% of samples with Diptera, Ceratopoganidae were in 8% of samples, Ephydridae were in 5% of samples, Simuliidae were in 4% of samples, Culicidae and Chaoboridae were in 4% of samples, and Syrphidae was in only one sample. A total of 14 Chironomidae genera and 21 species and forms were found; 9 of them are new for Crimea. Reduction of the dominance variants in the community, as well as the number of chironomid species, with increasing salinity may indicate an increase in the filtering role of salinity in the Diptera community species composition that is still poorly studied.