Vol 12, No 4 (2019)

This scanning electron microscopy study of phytoplankton from the watercourses and water bodies of the Mordyyakha River basin (Yamal Peninsula) has made it possible to expand the taxonomic spectrum of Bacillariophyta: a total of 281 taxa of specific and intraspecific ranks of diatom algae of 63 genera have been identified. Among them, 14 species and varieties are new for the flora of Russia and 30 forms of the 14 genera have been identified only to the genus level. The highest taxonomic diversity is recorded in Lake Pebtavyto (116) and the channel between two lakes (125). Diatoma tenuis, Encyonema silesiacum, Fragilaria vaucheriae, Tabellaria flocculosa, and Ulnaria ulna are the most widespread in the studied water bodies.

Long-term data (2009–2017) on the taxonomic structure of phytoplankton in small forest lakes of the Southern Ural region in the territory of the sulfide copper–zinc deposits and in the zone of impact of a copper smelting plant have been systematized. Patterns of changes in the species richness of phytoplankton towards a considerable decrease in the taxonomic diversity of phytoplankton have been determined in the gradient of increasing acidity, concentrations of heavy metals, and sulfate ion content. The species richness of golden algae increases in oligoacidic conditions of forest lakes in the buffer zones of technogenesis. The relationships between the structural parameters of phytoplankton and abiotic factors are analyzed.

The ecology and seasonal development of Ranunculus nipponicus in nonfreezing watercourses on the northern coast of the Sea of Okhotsk (59° N) have been studied. Year-round vegetation and flowering without the formation of a resting stage of the water crowfoot has been reported for the first time for the territory of Russian Federation. During all months of the year, the shoot growth, the formation of young roots, buds, and cleistogamous flowers are observed at an average monthly water temperature of +0.1°C to +5.8°C. The most intensive formation of young roots takes place in February–March and the underwater flowers appear en masse in late March–early April; neither phenomena are associated with an increase in water temperature. Cleistogamous flowering rarely leads to seed ripening, possibly due to a water temperature that is too low.

Annual changes in the quantitative characteristics and structure of zooplankton in the pelagic and littoral zones of Lake Sevan in October have been determined by a number of factors, among which the biomass of the main planktophage, whitefish (Coregonus lavaretus L., 1758), have the greatest effect. The richest communities form due to Cladocera upon a decreased biomass of whitefish, minimum increase in the water level, and high average monthly temperatures for the period of April–October. In the littoral zone, the zooplankton is affected by a number of unaccounted factors, and the influence of planktophagous fish, mainly inhabiting deepwater areas, is less pronounced. A significant increase in biomass of planktophagous fish in 2016–2017 leads to a reduction in the quantitative characteristics of zooplankton, resulting in decreased water clarity.

The drift parameters and indicators of the quantitative development of zoobenthos in the watercourses of this island in the Kuril Islands archipelago have been estimated for the first time. Hydrobionts drifting during the day are smaller than those drifting in the dark, which may be a consequence of the food selectivity of visually oriented drift-feeding fish. Since the upstream movement of zoobenthos contributes to the overestimation of the coefficients of a specific drift rate, it is proposed to use the drift intensity during one exposure of the net for calculations.

In the past 50 years, habitat conditions and distribution of sturgeons in the Caspian Sea have significantly changed. The longest term records of sturgeon distribution are obtained for the northern part of the sea, which is extremely important for the feeding of these species. In the present review, we summarize and analyze changes in the distribution of the beluga Huso huso L., 1758; Russian sturgeon Acipenser gueldenstaedtii Brandt, 1833; and stellate sturgeon Acipenser stellatus Pallas, 1771 in the northern part of the sea from 1970 until 2014 and the biotic and abiotic factors of these changes. The effect of the sea-level fluctuations, the biomass of food organisms, and the total abundance of the studied fish species on their distribution is demonstrated.

We have reviewed foreign and domestic literature devoted to the study of the amino acid (AA) composition of aquatic organisms representing major groups of producers (green microalgae and diatoms, and cyanobacteria) and primary consumers (zooplankton). Based on published data, we estimate the composition of essential and nonessential AAs of microalgae, cyanobacteria, and zooplankton and determine their differences. It is concluded that the AA composition of major groups of plankton is heterogeneous. The role of AAs as a limiting factor for the development of herbivorous zooplankton is discussed. The prospects and the need for further study of AA composition in order to develop a complete theory of functioning of aquatic ecosystems have been demonstrated.

The effects of 30-day exposure to Roundup at concentration of 2 μg/L and of thermal stress on the intestinal glycosidase activities (maltase and amylolytic activities (AA)), brain acetylcholinesterase (AChE) activity and water-soluble protein (WSP) content in juvenile specimens of Amur sleeper Perccottus glenii Dybowski have been studied. Additionally, critical thermal maximum (CTM) and final selected temperature (FST) are determined in fish of control (exposure to 0 μg/L Roundup) and Roundup-exposed groups. After Roundup exposure AA and WSP content were 27 and 31% lower respectively, maltase and AChE activities did not change. An increase in water temperature at a rate of 8°C/h decreased AA by 60%, maltase activity by 18% and WSP content by 28% in fish of the control group; but decreased AA by 76%, AChE activity by 29%, WSP content by 40%, and increased maltase activity by 11% in fish of the Roundup-exposed group. The recovery treatment during 12 days in a thermal gradient with herbicide-free water (temperature range between 14 and 31°C) reduced the inhibitory effect of heating on AA, but increased it the on AChE and WSP content in fish from both control and Roundup-exposed groups (on maltase activity only in the fish of exposed group). No significant differences were noticed in CTM and FST values in fish of control and Roundup-exposed groups.

On the basis of our own and published data, the contribution of autotrophic communities to the total primary production in the ecosystem of the Rybinsk Reservoir was estimated during the vegetation season in 2009. The contributions were as follows: 390 198 t C for phytoplankton, 6100 t C for epiphyton, 115 550 t C for macrophytes, and 1491 t C for phytobenthos. Higher aquatic plants constituted 74.4% of the total primary production in the littoral zone of the reservoir, which occupies 4.1% of the reservoir area.

At present, invasive fish species dominate in terms of abundance and compete for environmental resources and ecological niches with native species in some freshwater waterbodies and watercourses of Central Vietnam. This may ultimately lead to a decrease in the diversity and to the transformation of fish communities. Data on the distribution and biology of the mass alien species posing the most serious threat to tropical freshwater ecosystems, including in Vietnam—suckermouth-armored catfishes Pterygoplichthys spp. (Loricariidae) and Nile tilapia Oreochromis niloticus (L.) (Cichlidae)—are analyzed. These invasive species are shown to possess high adaptive potential. It is noted that invasions, as well as the intentional and unintentional introduction of alien fish species, may have negative consequences for the biodiversity of Vietnamese aquatic ecosystems.