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The results of a hydrochemical analysis of the consequences of an accidental fuel release in the Norilsk–Pyasino water system are presented. The pollution of watercourses in the catchment of Lake Pyasino (a nameless (Nadezhdinsky) creek, the Daldykan River, and the Ambarnaya River) with oil products, phenols, easily oxidizable and hard to oxidize organic matter (COD, PO, and BOD5), suspended solids, inorganic salts, and heavy metals at concentrations exceeding the background levels and MPC for fishery water bodies, as well as a temperature rise in waters of the nameless creek near Norilsk Heat and Power Plant 3 (CHPP-3), have been revealed. The contamination of the surface water decreases downstream in ascending order: nameless creek–Daldykan River–Ambarnaya River. The occurrence of oil products, phenols, and organic substances in the surface waters 2 months after the fuel spill is obviously due to their diffusion from the river bottom sediments, which accumulated a considerable quantity of heavy fractions of diesel fuel after the accident. Increased concentrations of Ca, Cu, Zn, Mn, Co, and Ni in the waters of the studied tributaries of Lake Pyasino are not directly related to the accident; they result from the general technogenic pollution of the territory and the increased geochemical background for these elements. Water contamination with oil products and phenols in the studied areas of Lake Pyasino (its central and northern parts) and the Pyasino River has not been detected. However, Pb concentrations exceed the MPC and Cd is recorded in the water, which is probably due to pollutants that accumulated in previous years.

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

Fish are recognized as the main source of physiologically important omega-3 long-chain polyunsaturated fatty acids, namely, eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), for human nutrition. However, muscle tissue contents of these fatty acids in diverse fish species, i.e., their nutritive value for humans, varied within two orders of magnitude. We reviewed contents of EPA and DHA, measured by similar methods using an internal standard during chromatography as mg per g of wet mass in 172 fish species belonging to 16 orders, to evaluate probable variations in phylogenetic and ecological drivers. EPA + DHA content varied from 25.6 mg g−1 of wet mass (Sardinops sagax) to 0.12 mg g−1 (Gymnura spp.). Multidimensional redundancy analysis revealed that among phylogenetic, ecomorphological and abiotic environmental factors, the highest proportion of variation contribution belonged to the shared contribution of sets of phylogenetic and ecomorphological factors. Specifically, the highest values of EPA + DHA content were characteristic of fish belonging to the orders Clupeiformes or Salmoniformes, were pelagic fast swimmers, ate zooplankton and inhabited marine waters or migrated from fresh to marine waters (anadromous migrations). High EPA and DHA content in muscle tissues of the above species appeared to be a metabolic adaptation for fast continuous swimming. In contrast to common beliefs, our meta-analysis did not support the significant influence of higher trophic levels (piscivory) and cold environments (homeoviscous adaptation) on EPA and DHA content in fish. However, many causes of high and low levels of physiologically important fatty acids in certain fish species remained unexplained and require evaluation in future studies.

We studied biogeochemical characteristics, including organic carbon and nitrogen contents, fatty acid (FA) composition, stable isotope ratios, and primary production in conjunction with species composition of bacterioplankton, using next generation sequencing, in the Yenisei River along a distance ∼1800 km. Basing on FA composition of particulate organic matter (POM) and on other indicators of sources of POM, the river was subdivided into four sections. The upper section 1, situated in mountain region, was the net source of high-quality autochthonous organic matter, produced primarily by diatoms and partly consumed by specialized bacteria species. Section 2 in plain taiga was net sink of high quality allochthonous and autochthonous organic matter, produced by cyanobacteria and green algae. Section 3 was net sink of organic matter, primarily allochthonous, consumed by the specialized species of bacteria. The lowest section 4, situated in tundra, was primarily the conduit of recalcitrant terrestrial organic matter, but also the net source of autochthonous organic matter, produced by diatoms. Biogeochemical traits of sections of the Yenisei River evidently shaped dominant species composition of bacterioplankton of these sections. Regarding the biogeochemical and microbiological data, we concluded that the Yenisei River ecosystem complexly combines features of river mosaic, river continuum, and “neutral pipe.”

An integrated study of the middle and lower Yenisei River was performed in the summer of 2012. It involved monitoring the key elements and ecological processes associated with the carbon cycle of the river ecosystem (the study area is more than 1800 km long). Measurements of the production and destruction processes have shown the failure of the “neutral pipe” hypothesis claiming that any river is a simple drain of carbon from terrestrial ecosystems to the ocean. The Yenisei River is not a purely heterotrophic ecosystem. It also has autotrophic areas, where the primary production of planktonic photosynthesis is higher than respiration (above the Angara River and near the Bolshaya and Malaya Heta rivers). According to the data, the respiration rate of the plankton community in the river depends mostly on the water temperature and the content of inorganic phosphorous that can restrict the amount of organic matter consumed by bacterioplankton.

The data set obtained in 19 experiments aimed at studying the growth of Daphnia of the longispina group on natural seston of the Bugach water reservoir (Krasnoyarsk) was used to analyze the relationship between the parameters of somatic and generative growth of the studied animals and the amount and quality of food. Depending on the quality of the seston, two models of the development of Daphnia were proposed. It was demonstrated that, despite the existing positive correlation between somatic and generative growth, a noticeable fraction of the variations of the specific rate of generative production is determined by external factors of the environment, such as the relative content of N and α-linolenic acid (N: C and ALA: C) in seston.

During two vegetation seasons (2004–2005), we compared feeding spectra of Arctodiaptomus salinus (Calanoida, Copepoda) populations inhabiting two neighboring salt lakes, Shira and Shunet, Khakasia, Russia, using fatty acid (FA) trophic markers. Sestonic FA composition in two lakes moderately differed, whereas levels of diatom FA markers were higher in Lake Shunet and of Cyanobacteria and green algae markers in Lake Shira. In general, markers in storage lipids—triacylglycerols (TAG) of A. salinus—reflected the differences in sestonic composition of the two lakes. Nevertheless, TAG fraction was also enriched by FA trophic markers of the minor components of seston, which were selectively ingested by the animals. In Lake Shira, A. salinus had significantly higher concentrations of bacterial FA markers in TAG. In Lake Shunet, TAG of A. salinus contained significantly higher relative amounts of 18:4ω3, 18:5ω3 and C22 polyunsaturated fatty acids (PUFA), which indicated marked contribution of cryptophytes or (and) flagellates into the diet. Laboratory experiments showed feeding on Cryptomonas and sulfur purple bacteria in Lake Shunet and ciliates and colonial picoplankton in both lakes, and generally confirmed the differences in FA trophic markers in A. salinus between the lakes. The two populations of A. salinus markedly differed in levels of essential long-chain PUFA, eicosapentaenoic (EPA) and docosahexaenoic (DHA) acids, although the levels of these FA in seston were quite similar between the two lakes. The higher levels of the essential ω3 PUFA in A. salinus in Lake Shunet may be an adaptive response of the animals to a vertical stratification of physico-chemical conditions and significantly higher salinity levels at the boundary of adjacent bottom layer in this lake.