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Simple Summary: Climate-related salinization of inland waters is observed in many regions of the world as a major environmental problem affecting natural processes in aquatic ecosystems. In order to better predict and control these changes, it is important to study the responses of aquatic fauna to increasing salinity. Macrozoobenthic fauna, which includes mollusks, small crustaceans, and insect larvae, constitutes the main food base for fish and water birds. Due to their relatively short life cycles, large species diversity, and high abundance, macrozoobenthos are the best indicators of changing water salinity. To determine the species richness, distribution, and salinity tolerance of macrozoobenthos, we investigated 17 small rivers with different water salinity in the southern arid region of the East European Plain. The study shows that the species richness gradually decreases with an increase in water salinity in the rivers. In freshwater rivers, the macrozoobenthos fauna includes more than 100 species, whereas, in hypersaline rivers with salinity comparable to seawater, only 10 species were found. A total of 5 of the 156 invertebrate species can be used as indicators of water salinization in rivers of the arid regions of Europe. This study investigated the species composition, distribution, and salinity tolerance of macrozoobenthos in 17 small rivers in the southern arid region of the East European Plain, which are characterized by a small channel gradient, slow-flowing or stagnant water bodies, and a wide range of water salinity, varying between 0.18 and 30 g L−1. In total, 156 taxa were found, among which 66 were Diptera species. The study revealed that the formation of benthic communities in the rivers is influenced by natural factors of the catchment basins, including the flat landscape with sparsely developed relief differentiation, climate aridity, and the widespread occurrence of saline soils and groundwater, largely related to the sedimentation of the ancient Caspian Sea and modern climate changes. These conditions are favorable for the occurrence of lacustrine macrozoobenthic species in freshwater, euryhaline, and halophilic ecological groups. The investigation revealed a decrease in species richness in response to an increase in water salinity. The five identified halophilic species Tanytarsus kharaensis, Glyptotendipes salinus, Cricotopus salinophilus, Chironomus salinarius, and Palpomyia schmidti can be used as indicators of river ecosystem salinization. [ABSTRACT FROM AUTHOR]

The rise of salinity of inland waters in many regions of the world highlights the necessity of investigations of ecosystems with a naturally high level of salinity to be able to predict possible changes in freshwater under the influence of modern environmental hazards. We studied species composition, density, biomass, and estimated production of macrozoobenthos communities in the middle reach and mouth of the saline Chernavka River (Lake Elton basin, Russia) from October 2018 to September 2019. The salinity of the water varied from 24 to 34 g l−1 during the investigation period. Species richness was poor: only a total of 21 taxa were found during the study period in the Chernavka River. The average density of benthic taxa in the middle reach was 8294 ind. m−2, and in the river mouth, the average density of benthic taxa was 12,893 ind. m−2. Chironomid larvae and Ceratopogonid larvae had high density and biomass in both sites throughout the growing season. Beetle larvae had high density in summer and autumn in the mouth of the river. The production of macrozoobenthos in the middle reach was 57.7 g dry wt m−2 year−1. In the mouth reach, the production was 707.2 g dry wt m−2 year−1. In the middle reach, the greatest contribution to production was made by Palpomyia schmidti, Cricotopus salinophilus, and Ephydra sp. In the mouth reach, Chironomus salinarius, Berosus spp., and C. salinophilus contributed to benthic production the most. [ABSTRACT FROM AUTHOR]

The Kuril Islands stretch southwest from Kamchatka, Russia, to Hokkaido, Japan and separate the Sea of Okhotsk from the northern Pacific Ocean. A series of transgressions and regressions linked to variations in climatically affected global ice volume are among the most important drivers of Holocene environmental changes in the region. Despite a long research history, reconstructions of the Holocene palaeoenvironment are sparse with inconsistent interpretations, arising from insufficient dating control, different temporal resolutions, and specific local geographical features, such as high tectonic activity and the isolated nature of the area. We have investigated a 550 cm lake sediment section from Iturup Island, the largest among the Kuril Islands. The 6600 year old sediment section was studied using sedimentological, geochemical, chironomid, diatom, and pollen analyses to reconstruct environmental and climatic changes and sea level fluctuations (transgression – regression stages). During the warm late phase of the Middle Holocene (6600–4400 cal BP) an open bay or lagoon with shallow overgrown littorals existed at the sampling site. The cooling between 5600 and 4400 cal BP can be correlated with Neoglacial cooling. The cool period between 4200 and 3200 cal BP was a transition towards the formation of a freshwater lagoon and can be related to a decline of the Japan Late Jomon transgression (Sakaguchi, 1983). Between 3200 and 2800 cal BP the lagoon separated from the marine environment in response to a further sea level decrease during the Japan Latest Jomon cold stage and regression. The following increase in the share of broad-leaved pollen indicated a slight warming (Yayoi transition stage) that was interrupted by a short-term cooling spell between 1500 and 1400 cal BP (cold Japan Kofun stage). The period between ca 1100 and 800 cal BP can be related to the European Medieval Climate Anomaly (MCA) or relatively dry Japan Nara-Heian-Kamakura warm stage. The Little Ice Age cooling and Edo regression were evident after ca 800 cal BP. Modern warming however is not well seen in the investigated core. [ABSTRACT FROM AUTHOR]

Saline rivers are supposed to be ‘hot spots’ of high biological productivity in arid landscapes. To test this, we quantified the production of chironomid larvae, because river production is known to be transferred to arid landscapes primarily by birds fed on these larvae. In addition, we studied the potential biochemical quality of the larvae for birds based on the essential highly unsaturated fatty acid (HUFA) contents in their biomass. We studied species composition and measured production of chironomid larvae in two saline rivers (Volgograd region, Russia). We also evaluated the fatty acid composition and contents of the dominant taxa and estimated the flux of HUFA from the studied saline rivers to land via chironomid potential emergence. Average monthly production of chironomids measured for only 1 month, August, was quite comparable to annual production in some freshwater rivers. All the dominant chironomid larvae had comparatively high essential eicosapentaenoic acid contents, especially Cricotopus salinophilus, which showed the highest value, reported for Chironomidae. The monthly flux of HUFA from the studied rivers to land due to the chironomid potential emergence was roughly comparable to the global average estimation of annual water–land HUFA export via emerging insects. [ABSTRACT FROM AUTHOR]