Том 12, № 1 (2019)

This paper presents a review of the development of basic concepts that describe the organization of river ecosystems. The first zonal models of river description, as well as the transition to continuum concepts and their further criticism and the development of discontinuum models, are considered. The main discrete models are given as the best alternative approaches to describing the organization of the river ecosystem. The main trends of the development of ideas of the hierarchy of organization of river systems and their transformation into contemporary complex concepts are presented.

An illustrated description of two species of free-living nematodes of the family Linhomoeidae Filipjev, 1922, new to science, found in the sediments of a thick mangrove forest in the Yên River, Vietnam, is presented. Desmolaimus minor sp. n. is morphologically similar to D. calvus Gerlach, 1956, but has a shorter body, two-separate internal cavity of pharynx, and setiform labial and cephalic sensilla. A review of species of the genus Desmolaimus de Man, 1888 is made, and a pictorial key to determinate valid species of this genus is provided. Terschellingia yenensis sp. n. is similar to T. lissa Timm, 1962 and T. longissimicaudata Timm, 1962. It differs from T. lissa by the presence of precloacal supplements in males, the presence of cervical setae, a longer tail, and shorter spicules; it differs from T. longissimicaudata by a comparatively longer tail, shorter spicules, and a longer dorsal apophysis of gubernaculum.

Our goal was to assess the impacts of zebra mussels on the components of the microbial loop (dissolved organic carbon, bacteria, nanoflagellates and ciliates) and their relationships with classic food web components (algae, rotifers, crustaceans) in mesocosm experiment. Zebra mussels were added to mesocosms that were filled with water from a mesotrophic lake (Mazurian Lake District, Poland). Zebra mussels increased concentrations of chlorophyll and caused short-term negative effects on the biotic components of the microbial loop just after the onset of the experiment. Grazing pressure by zebra mussels caused shifts in the taxonomic and trophic structure of ciliates from small species feeding on algae and bacteria to small bacterivorous species. As a result of zebra mussel introduction, the trophic interactions between the components of microbial loop and classic food chain were altered relative to control.

The results of a study of periphyton algae in the Zeya River and nine watercourses of its drainage basin (Amur Oblast) are presented. The composition of dominant species is determined, the structural features of algal communities are considered, and quantitative characteristics of some of their components are obtained. The total abundance of phytoperiphyton in the Zeya River is 583 billion cells/m²; biomass is 102–1106 g/m². In medium-sized watercourses, the total abundance of algae ranges from 16.2 to 100 billion cells/m²; biomass is from 2.0 to 18.3 g/m². Most of the biomass is formed by diatoms (Encyonema silesiacum, Hannaea arcus, Ulnaria ulna, Gomphoneis olivaceum, and large-celled species of the genus Gomphonema); most of the abundance is formed by cyanobacteria and diatoms from the genera Achnanthes, Fragilaria, Gomphonema, and the species Encyonema minutum.

Based on the example of one of the Timan watercourses (the Vym River) in the zone influenced by the Middle Timan bauxite mine, it is shown that the first stage of its exploitation has led to a considerable increase in the number of recreational anglers in nearby waterbodies, which has resulted in a decrease in the diversity of the fish population in the upper reaches of the Vym River, as well as in a decrease in the abundance of economically valuable fish species populations, the long lifespan of which has been reduced to the medium age.

The forage base of juveniles of salmonids (Atlantic salmon and brown trout) from six rivers of the Lake Onega basin has been analyzed: invertebrate organisms of 23 taxa have been identified. In the macrozoobenthos samples, the content and ratio of fatty acids (FAs) of total lipids are determined. Differences in the ratio of essential 18:3ω-3/18:2ω-6 FAs are found, and the ratio is higher in zoobenthos collected from “salmon” rivers than in those of “brown trout” rivers (within 1.68–2.83 and 0.44–1.08, respectively). The ratio of saturated FAs/polyunsaturated FAs (0.66–0.97 and 0.33–0.59, respectively) in the zoobenthos from salmon rivers is higher than in forage from the brown trout rivers. The content and ratio of physiologically important FAs in the feeding objects of young fish of salmonids have a significant effect on their growth and development.

Using the example of Lake Krugloye (Mordovinskaya floodplain in the Saratov Reservoir), the changes in the physiological and biochemical parameters in two abundant fish species inhabiting the same biotopes have been comparatively analyzed. The fish under study are the aboriginal crucian carp (Carassius auratus gibelio) (Bloch, 1792) and the invasive Amur sleeper (Perccottus glenii) (Dybowski, 1877). The study reveals differences between the species in the patterns of the dynamics of body weight and contents of protein, fat, water, and caloric contents upon an increase in body length during various months of the active feeding period. Potential reasons for the differences and their consequences are discussed.

The state of the antioxidant system and the intestinal microbiocenosis in Danio rerio (Hamilton, 1822) have been studied with the use of nickel and its oxide nanoparticles released into environments. It is revealed that the nanoparticle-induced toxic effect causes oxidative stress, followed by restructuring of the intestinal microbiocenosis and inhibiting the protective mechanism. A low loading dose and a short period of exposure of the test object to the nickel nanoforms activate the antioxidant defense system of the body in response to the free radical evolution. Chronic conditions and high doses exhaust the antioxidant system under the effect of free-radical hyperproduction during oxidative stress. A change in the microorganism species diversity is ascertained; for instance, Rhodobacter and Methylobacterium replace Citrobacter and Enterobacter, respectively, with the introduction of the nickel oxide nanoparticles, while Bacillus, Acinetobacter, and Rhodobacter replacement occurs with the introduction of nickel nanoparticles. Therefore, the transient microorganisms tend to replace the normal intestinal flora. An increase in the environmental total amount of nickel in the nanoparticle form results in its accumulation in the body of hydrobionts under the effect of the induction of chronic conditions.

The content of dry matter, copper (Cu), and cadmium (Cd) have been studied in five species of brown algae and one species of higher plants at six sampling sites in the Chupa Inlet of the Kandalaksha Bay of the White Sea. Despite a common natural geochemical background, a variability in the content of Cu and Cd has been observed in algae species which have similar systematic positions. No simple functional relationship could be established between the dry matter content and content of metals. Copper affects the accumulation of cadmium only when the Cu content is high. Species of the family Fucaceae (Fucus vesiculosus, F. serratus, and Pelvetiacanaliculata) accumulated Cu and Cd most effectively. The minimum content of Cd was found in the leaves of Triglochinmaritimum.