Vol 17, No 6 (2024)

A total of 53 diatom species, varieties and forms are found in the phytoplankton of the Krasnoyarsk Reservoir using scanning electron microscopy. Among them, 24 are new for the reservoir, including 3 new for the flora of Russia ( Achnanthidium minutissimum var. inconspicua , A. pseudolineare , Sellaphora obesa ), which makes it possible to expand the species composition of the Yenisei up to 184. The findings of the Baikal endemics Didymosphenia geminata and Hannaea baicalensis , as well as the Ob form Aulacoseira ambigua f. curvata expand the ranges of these alga.

The article describes the musculature of the body, the pharynx and the ventral disc of Aspidogaster limacoides. The body wall contains three muscle layers: circular, longitudinal and diagonal. Numerous chordal muscles oriented both transversely and longitudinally, along with body wall and radial musculature, precondition the oral funnel mobility. Apart from radial, the pharynx musculature includes outer longitudinal, inner circular and outer circular muscles, the latter forming the anterior sphincter. The ventral disc being alveolar in its structure, the diversity of its musculature is restricted: the septa contain no chordal muscles or sphincters. The architectonics of parenchymal musculature has three main features resulting from large disc size, i.e. the presence of two muscle septa in the parenchima, dorso-ventral musculature being located latero-ventrally from muscle septa and a considerable development of viscero-motor muscles.

The excessive intake of biogenic elements into water bodies leads to the active development of planktonic algae, water bloom pathogens, which mostly include cyanobacteria. In vitro studies have allowed us to test a working hypothesis on the absence of any inhibitory effect of metabolites of the Chlorella vulgaris BIN strain on the CALU 799 Dolichospermum spiroides (Klebhan) Wacklin, L. Hoffmann & Komárek and CALU 1749 Planktothrix agardhii (Gomont) Anagnostidis & Komárek cyanobacterial cultures in working concentrations of 1 : 1, 10 : 1, 100 : 1, and 1000 : 1 (cyanobacteria : chlorella). In a series of experiments, no effect of chlorella culture on the viability of cells of the studied cyanobacteria has been detected. However, high cyanobacteria densities (concentrations of 1 : 1, 10 : 1, 100 : 1, and 1000 : 1) are associated with an increase in the number of dead chlorella cells. The toxic effect of the CALU 799 D. spiroides strain is more pronounced in comparison with that of CALU 1749 Planktothrix agardhii.

New data on the dynamics of pigment characteristics for different silts in the basin-valley Rybinsk Reservoir, the largest source of fresh water on the Upper Volga, are presented. The concept of eutrophication of the reservoir under modern climate warming is supplemented. The content of pigments in bottom sediment cores taken after 10 years (in 2009 and 2019) was compared. According to the latest survey, the average content of chlorophyll a with pheopigments in cores at the stations is characterized by higher values, and the carotenoid/chlorophyll ratio (index Е ₄₈₀ /Е ₆₆₅ ) is lower than according to the first survey. The relationship between the index Е ₄₈₀ /Е ₆₆₅ and the total content of chlorophyll a and pheopigments in cores from most stations is negative, as in phytoplankton. In the total array of studied sediment samples, the contribution of pigment concentrations (chlorophyll a + pheopigments) belonging to the hypertrophic category is increased. The average content of sedimentary pigments in lake-like areas increased compared to riverine areas. The dynamics of pigments is clearly expressed in cores of gray clayey silt and smoothed in peat–originated silt. Over the period from 2009 to 2019, the average contribution of autochthonous organic carbon, estimated from the sum of chlorophyll and pheopigments, increased from 7.7% to 12.3% of total organic carbon in cores. The trends of the pigment concentrations in cores indicate an increase in the trophic state of benthal to date. The significance of the pigment characteristics of bottom sediments for monitoring the benthal productivity over the entire period of reservoir operation is discussed.

The article discusses mo rphometry, hydrochemistry, zooplankton and macrophytes of three unique “round” lakes of the Nadym River basin (Western Siberia, Yamal-Nenets Autonomous Okrug). Significant depths, weak lakeshore angularity, zero color of water and predominance of sulfates in the ionic composition are atypical for the northern taiga lakes of Western Siberia. Coastal aquatic vegetation is characterized by extremely low species richness with dominance of Sparganium angustifolium , which is an indicator of high-transparent ultrafresh oligotrophic waters. Dominant complexes were formed in planktonic communities represented by 1–2 species with a high level of dominance. According to the level of development of total zooplankton biomass the lakes belong to the ultra- and oligotrophic types.

The paper analyzes the modern structure and food relations of the fish population of the small glacial lakes of the Urals. The features that are expressed primarily in the reduction of the species richness of the local ichthyofauna and the predominance of a single-species fish population are revealed. The number of fish species inhabiting these reservoirs correlates with the height of their location above sea level, the area and the value of the redox potential of water. It is shown that the fish population of many small Ural lakes of the Pechora River basin is formed by a single species. It is established that the single-species fish part of the aquatic communities of mountain lakes can be represented by Arctic char, Siberian and European grayling, pike, lake and common minnow, roach and perch. The maximum number of such lakes was found in the highest mountainous region of the Circumpolar Urals. The relative abundance of fish and shifts in the trophic structure of the fish part of aquatic communities are considered. Fish-ichthyophages mainly switch to eating invertebrates, while cases of cannibalism are rare. The data obtained are analyzed from the standpoint of modern ideas about the glacial history of the Urals.

The size, age, sex structures of pikeperch Sander (L.) from Lake Necheritsa (Sebezhsky National Park) have been studied, as well as linear growth using back-calculation according to the Leo direct dependence function. Growth of pikeperch is described formally by linear equation L ( t ) = 5.4 × x + 0.2 (cm). The length frequencies of individual age groups are normally distributed, which corresponds to ideas about linear fish growth. The population is represented by 13 age classes, the maximum length of an individual in the sample is 872 mm. The analysis of the diet showed the presence of 6 mass fish species observed in the catch, including the young pikeperch; the ratios of individual species in the diet and the sample indicates an absence of electivity of nutrition. According to the estimates, the proportion of pikeperch in the ichthyocenosis in the period 1989–2022 in the Lake Necheritsa has increased by ~ 8 times. A comparative analysis of the linear growth of pikeperch from populations of different regions under environmental conditions, differing in a number of values of key parameters, is carried out. Growth rates of pikeperch from southern populations are generally higher and more consistent with asymptotic growth, while the size limits and life expectancy are generally higher in northern populations. A hypothesis has been tested about the causes of differences in the nature of linear growth.

The paper examines the influence of pre-spawning and post-spawning planktophagous and ichthyophagous fish migrations on the invasion degree of nematode Hysterothylacium aduncum (Rudolphi., 1802) in the northern part of the Azov-Black Sea basin. For the first time, a decrease in the parameters of invasion with an adult nematode in herring during its wintering in the Black Sea has been shown, compared with similar indicators during the period of post-spawning migration after spawning in the Azov Sea. According to the authors, the diet change is the main cause of the difference in the invasion rate of migrating planktophagus as well as ichthyophagous fish. The authors consider that one of the indirect reasons for the differences in the invasion values of migrating fish is the inequality in salinity in disparate water areas of the northern parts of the Black and Azov Seas.

Significant individual variation of nitrogen and carbon isotope composition (δ ¹⁵ N and δ ¹³ C values) in white muscle tissues was found in samples of three cyprinid fish species, Cyprinion macrostomus (periphytonophage), Cyprinion kais (benthophage), and Luciobarbus schejch (omnivore), collected in a small tributary of the upper Tigris system (Turkey). In particular, exceptionally low value (1.7‰) and abnormally wide intraspecific variability (from 1.7 to 15.8‰) of δ ¹⁵ N were observed in C. macrostomus . Despite samples were collected synchronously and syntopically, very broad range of δ ¹⁵ N values points out possible heterogeneity of the samples. The studied watercourse is located in the zone of agriculture with intensive chemicalization and pollution of the river by mobile forms of nitrogen (mostly ammonium) could play a significant role in lowering δ ¹⁵ N values, especially in the periphytonophage. Along with that, fish with high (normal) δ ¹⁵ N values are supposedly recent migrants that came from a large river for joint spawning with resident fish. The pollution of water bodies as well as the presence of migrations should be taking into account in stable isotope analyses-based studies on trophic ecology of fishes.

The article presents for the first time the data on cyanobacterial toxins and the genes of their biosynthesis in the phytoplankton of the mesotrophic Lake Pleshcheyevo Yaroslavl Region, during the period of cyanobacterium Gloeotrichia echinulata (Smith et Sowebry) Richter – bloom. In the phytoplankton of the lake, the presence of hepatotoxins microcystins was recorded using chromatography – mass spectrometry; in DNA isolated from plankton, the mcyE gene for the biosynthesis of these cyanotoxins was detected using PCR. During the study period, other types of cyanotoxins (cylindrospermopsin, anatoxin – a, saxitoxins) and the presence of genes for their synthesis in the phytoplankton were not identified. In thirty colonies of G. echinulata isolated from the lake, the microcystin biosynthesis genes mcyA and mcyE were absent, which is consistent with their inability to produce cyanotoxin. Using molecular methods, the potential ability to biosynthesize microcystins in Microcystis aeruginosa and species of the genus Dolichospermum inhabiting in the lake was demonstrated. The paper discusses the toxicity of Gloeotrichia echinulata and the need for further long-term monitoring of toxigenic cyanobacteria in Lake Pleshcheyevo.