Vol 10, No 1 (2017)

A new diatom species Amphipleura vavilovii sp.nov. is described from water ecosystems of South-Eastern Asia (unnamed river flowing into ecological village Namlik, Laos). Species is illustrated by original LM and SEM microphotographs. Description is given on the basis LM and SEM data.

The species composition and distribution of testate amoebae in Bau Sen and Bau Trang lakes (Binh Thuan Province, Vietnam) were investigated. Fifty-three species, varieties and forms have been identified from the water column and sediments. Twenty-seven species, varieties and forms from the genera Arcella, Centropyxis, Cyclopyxis, Difflugia and Pyxidicula were found in Vietnam for the first time. The updated list of testate amoebae in Vietnam now includes 286 taxa. The genera Arcella, Centropyxis and Difflugia are characterized by the highest frequency of occurrence. The species diversity of Arcella, Centropyxis, Difflugia was the highest. Centropyxis aculeata, Arcella discoides, Difflugia schurmanni, Netzelia oviformis and Difflugia limnetica were the most common species. Many species have shown restricted distribution, some species have been found only in one lake and not been found in another lake. The number of observed species, varieties, and forms in each lake is 34. The average number of the species per sample on the shores of the lakes subjected to human agricultural activity was significantly higher than in the samples from the shores of the lakes with less anthropogenic disturbance. The curves of “cumulative species number vs. sampling effort” are well fitted by equations S = 7.60 N^0.69 for Bau Sen lake and S = 12.52 N^0.46 for Bau Trang. The curves are unsaturated, which indicates that more intensive investigations of testate amoebae should be expected to reveal more species.

The abundance and biomass of the main components of the microbial plankton food web (“microbial loop”)—heterotrophic bacteria, phototrophic picoplankton and nanoplankton, heterotrophic nanoflagellates, ciliates and viruses, production of phytoplankton and bacterioplankton, bacterivory of nanoflagellates, bacterial lysis by viruses, and the species composition of protists—have been determined in summer time in the Sheksna Reservoir (the Upper Volga basin). A total of 34 species of heterotrophic nanoflagellates from 15 taxa and 15 species of ciliates from 4 classes are identified. In different parts of the reservoir, the biomass of the microbial community varies from 26.2 to 64.3% (on average 45.5%) of the total plankton biomass. Heterotrophic bacteria are the main component of the microbial community, averaging 63.9% of the total microbial biomass. They are the second (after the phytoplankton) component of the plankton and contribute on average 28.6% to the plankton biomass. The high ratio of the production of heterotrophic bacteria to the production of phytoplankton indicates the important role of bacteria, which transfer carbon of allochthonous dissolved organic substances to a food web of the reservoir.

Studies conducted in January to March at different parts of the Rybinsk Reservoir, in lakes of various types, and in a pond have demonstrated that the processes of СН₄ cycle during the ice period play an important role in the destruction of С_org and functioning of the ecosystem food webs. In highly trophic polluted lakes, the formation of СН₄ takes place both in silts and in the water column, and its gross production reaches a high summer level of 540–1220 mg С_org/(m² day). Taking into the account methanogenesis, 68–97% of the destruction of organic matter (OM) occurs due to the processes in bottom sediments. In the silts of productive lakes, only anaerobic processes cause the destruction.

The pigment composition of phytoperiphyton algocenoses on stones and macrophytes (Potamogeton lucens L., P. perfoliatus L., P. gramineus L., P. pectinatus L., Mirophyllum spicatum, Petasites hybridus (L.) Gaertn., Mey. et Sxherb, Nuphar lutea L., and Alisma plantago-aquatica L.) in the submontane Sylva River (Middle Ural) is considered based on the surveys of 2000–2012. The wide variability in the content of plant pigments in phytoperiphyton depends on the season and type of substrate. The maximum values similar for all substrates are observed at the end of summer. The concentrations of Chl a increase during warm low-water years. Chlorophyll a prevails among green pigments in periphyton; the relative concentration of other pigments is lower. The concentration of plant carotenoids in epiphyton is slightly higher compared to epilithon and is comparable to the Chl a level. The trophic state index of the Sylva River may be determined as mesotrophic or weakly eutrophic when the Chl a concentration in phytoperiphyton is used as a marker.

The features of overgrowing of different types of protected shallow waters in the Ivankovo, Uglich, and Gorky reservoirs have been considered. The average degree of overgrowing increases in the following series: pocket-type shallow waters (37.3% of area), shallow waters behind islands (40.6), and bays (56.9). Helophytes contribute to the overgrowing of more than 50% of all types of protected shallow waters. The composition of plant community dominants of protected shallow waters of different types is very similar, because the reservoirs belong to the same cascade, are located in one climatic zone, and have similar ecotopes. The effect of morphometric parameters (area, volume, length, average width and depth) and their ratios (oblongness of water area, openness, and isolation) on the overgrowing of protected shallow water areas is expressed only at average values of these parameters and has an exponential form. The contribution of the area isolation to overgrowing is most significant (up to 55%).

An experimental study on the zooplankton community in the thickets of elodea Elodea canadensis Michx. of different densities (2, 4, and 8 g/L, wet weight/L) has been conducted. It is revealed that specific cationic composition and pH and sharp daily fluctuation of oxygen concentrations is a characteristic of the water in dense thickets of plants. Changes in water chemistry and in spatial organization of the environment influence zooplankton diversity and population dynamics of some species. With an increase in density of thickets, the number of Daphnia longispina O.F. Müller decreases, while the share of predators (Cyclopidae and Polyphemus pediculus O.F. Müller) increases. The abundance of Ceriodaphnia quadrangula (O.F. Müller) increases in the presence of plants, but does not depend on the density of the thickets. The correlation between the development of Simocephalus vetulus (O.F. Müller) and Diaphanosoma brachyurum (Liévin) and water cationic composition, changing in the process of growth and senescence of plants, is revealed.

Oxidative stress causes damage to cell components by reactive oxygen species (ROS) originating from the effect of various chemical pollutants, such as heavy metal cations, polyaromatic hydrocarbons, organochlorine and phosphororganic pesticides, polychlorine biphenyls, dioxins, and other xenobiotics. To avoid pathological consequences of interaction between biological molecules and high-reactive ROS, cells have a detoxification mechanism that uses glutathione, a nonprotein thiol. Glutathione is a component of cellular protection against the toxic action of xenobiotics and metal cations. In the last decade, the effect of environmental pollutants on changes in glutathione concentrations in tissues of aquatic organisms has been touched on in a large number of works. This review summarizes data of the up-to-date studies on glutathione variability in fish tissues under the effect of biogenic and industrial xenobiotics.

Methods for evaluating the motivational component of the fish rheoreaction (ratio of rheoreaction types) are developed and tested in a circular hydrodynamic tank for three fish species (Danio rerio, Poecilia reticulata, and Inpaichthys kerri). Three rheoreaction types of fish were distinguished: a positive type (fish movements against water current), a negative type (fish movements along with water current), and a compensatory type (fish maintaining their position in relation to immobile reference points). The main distinguishing features of these new methods are unrestricted distance for fish movements, continuous monitoring of individual fish movements (video recording), and evaluation of ratio between the types of rheoreaction in terms of duration of demonstration of these types by each. The minimum required observation time and water current velocities are determined. It is shown that these methods can be used for investigating the types of rheoreaction in different fish species. Every single individual repeatedly demonstrated all these three rheoreaction types during the test.

Test systems using multiplex PCR and restriction analysis have been designed for the simple and rapid identification of two widespread species of roach, Rutilus rutilus and R. lacustris, characterized by the sympatric zone. This method is based on the variation of nucleotide sequences of the mitochondrial markers (cytochrome oxidase I subunit and cytochrome b); it allows identifying the species omitting the DNA sequencing.