Limnology and Freshwater Biology

Current state of the ecosystem of Lake Vedlozero and its biological resources (Republic of Karelia, northwestern Russia)

Sidorova A.I., Syarki M.T., Slastina Yu.L. — Wed, 26 Feb 2025 00:00:00 +0800

The results of a study of the current state of the ecosystem of Lake Vedlozero (Republic of Karelia, northwestern Russia) in 2021-2022 and its changes over 30 years are presented. In recent years, in the summer-autumn period, algal blooms, including toxic cyanobacteria, have intensified in the lake, which affects the quality of the water and fish habitat. Active algal blooms are still local and are observed mainly in areas of the lake with intense anthropogenic impact. In general, the Lake Vedlozero ecosystem at the present stage corresponds to mesotrophic status in terms of hydrochemical and hydrobiological indicators.The lake’s aquatic communities have not undergone noticeable changes since the 90s of the last century. The concentration of chlorophyll a has increased by an order of magnitude (3 µg/l in 1992 and 11-90 µg/l in 2021). Planktonic communities are in a stable state and provide a stable food supply for planktivorous fish. The composition and structure of benthic communities also did not change over the 30-year period.To calculate fish productivity, an analysis of the distribution of organic matter and energy in the food web of the lake ecosystem was carried out using the balance model of V.V. Boulion. The results of the model calculation are in good agreement with empirical data. Thus, the model can be used for calculating fish production and estimating possible catches in the lake. According to the model, possible catches amount to a third of fish production and are equal to 9.6 kg/ha. For the first time in 2021, an alien species of the American rotifer Kellicottia bostoniensis was recorded in Lake Vedlozero, which may indicate that the range boundary of this species is moving northward against the backdrop of continuing warming of the regional climate in northwestern Russia.

Euphotic zone depth according to measurements of the photosynthetically active radiation profile of Lake Teletskoye in August 2023: regional features

Wed, 26 Feb 2025 00:00:00 +0800

The work analyzed measurements of the profile of photosynthetically active radiation (PAR) in Lake Teletskoye, obtained in August 2023. It was found that in the areas where rivers flow into the lake, the rate of vertical attenuation of photosynthetically active radiation is less than in the rest lake aquatorium. The maximum values of 0.577 m^-1 were found in the northern part of the lake, the minimum - 0.247 m^-1 in the central part of the lake, exposed to the river Chelyush runoff. All this indicates that the main source of dissolved organic matter is the degradation processes of organic matter in the lake itself, which are not associated with its supply due to river runoff. An estimate of the average PAR value attributable to the upper mixed layer was obtained. The range of its variability was from 0.13 to 0.62, which is also associated with river inflow.

Trophic state of the Kizhi skerries area of Lake Onego and water quality assessment based on summer phytoplankton indicators

Smirnova V.S. — Wed, 26 Feb 2025 00:00:00 +0800

The study of summer phytoplankton (July-August 2020 and 2022) in the Kizhi skerries area of Lake Onego revealed high quantitative indicators of phytoplankton development, which characterises this area as meso-eutrophic. The phytocenosis was characterised by high species diversity, which is typical for the summer phytoplankton community of Lake Onego. However, at the time of the study, the indicator species of β-mesosaprobic pollution zones (water quality class 3, satisfactorily clean) exhibited the greatest quantitative development. Notable species with the potential to produce cyanotoxins were observed, although their quantitative development was relatively limited. The analysis of multi-year changes revealed an increase in the abundance of cyanobacteria, green algae and euglena algae. The total biomass of phytoplankton increased as a result of the proliferation of numerous, small-celled cyanobacteria and a limited number of large-celled, benthic and planktonic-benthic diatom algal species. The marked proliferation of phytoplankton in the study area is attributable to the prevailing natural conditions. Further research is required to ascertain the precise reasons for the observed increase in phytoplankton quantities in recent years.

Assessment of water quality in the area of Kizhi Museum-Reserve (Lake Onego) by bacterioplankton indicators in summer of 2023

Makarova Е.М. — Wed, 26 Feb 2025 00:00:00 +0800

In summer 2023 the size and morphological structure of bacterioplankton, quantitative indicators of ecological-trophic groups of bacteria and total coliform bacteria were determined in the area of Kizhi Island a water body of Lake Onego. The morphological structure of the cells was dominated by bacilliform bacteria, indicating the presence of easily mineralizable organic matter (OM). The total bacteria abundance, heterotrophic and saprophytic groups of bacterioplankton confirmed the increased content of easily mineralizable OM in the area of Kizhi skerries. The development of phenol-oxidizing and hydrocarbon-oxidizing bacteria revealed water pollution with phenolic compounds and oil products. High indicators of total coliform bacteria indicated the presence of opportunistic microorganisms, the number of which almost everywhere exceeded the norms for waterbodies of recreational use. The most polluted area of Kizhi skerries is the western part, characterized by active shipping and low water exchange.

Variability and systematic status of Siberian spined loach Cobitis melanoleuca (Cypriniformes; Cobitoidei) in the Baikal region

Bogdanov B.E. — Wed, 26 Feb 2025 00:00:00 +0800

Siberian spined loach Cobitis melanoleuca (sensu lato) is distributed in the Northern Eurasia, and the Baikal region is the center of an areal of this species (or group of species). The present study analyzed the variability of exterior traits in eight populations of Siberian spined loach in the Baikal region (original data) and in the whole range (literature data). The results of the study have shown a high polymorphism of traits traditionally considered species-specific. It was found that populations of spined loaches inhabiting the Cisbaikalia are a mixture of phenotypes typical of Cobitis melanoleuca (sensu stricto), Cobitis granoei, and Cobitis olivai. It has been suggested that this may be caused either by the conspecificity of these taxa or by their hybridization. The refined data on nomenclature and diagnostic traits of taxa included in the synonymy of Cobitis melanoleuca (sensu lato) are presented in this study. It is suggested that at the current level of study of Siberian spined loach C. melanoleuca, it is reasonable to consider it as one polymorphic species, without division into vicariant forms.

Geobotanical maps of Pribaikalye

Molozhnikov V.N. — Wed, 26 Feb 2025 00:00:00 +0800

This study presents original geobotanical maps that reconstruct natural vegetation on the shores of Lake Baikal 40-50 years ago. It includes six maps, among which of particular importance are: a schematic map of the vegetation of the South-West Pribaikalye, a geobotanical map of the Baikal State Nature Reserve and a map of the cadastral assessment of the vegetation cover of the South Pribaikalye. These maps can be used for a retrospective assessment of changes in the vegetation cover under the influence of natural and anthropogenic factors.

Influence of 17α-Methyl Testosterone Infused Diets on Growth and Tissue Integrity in Oreochromis niloticus (Linnaeus, 1758): A Laboratory Study

Rahman H.B., Khan M.A., Sultana S. — Wed, 26 Feb 2025 00:00:00 +0800

In this study, the effects of varying concentrations of 17α-methyl testosterone (17α-MT) in the diet on the growth performance, survival rate, and histopathology of Nile tilapia - Oreochromis niloticus (Linnaeus, 1758) were investigated. Four different hormone doses, 0 mg/g (control), 0.5 mg/g, 0.7 mg/g, and 0.9 mg/g were administered with the diet of O. niloticus for 120 days. Growth performance, as measured by the increase in total length (12.98 ± 1.26 cm) and total weight (18.99 ± 2.36 g), was highest in O. niloticus receiving 0.9 mg/g 17α-MT diet. The total weight (TW) increase was significantly more pronounced than that observed in total length (TL). In the average growth of length (31.13%) and weight (43.16%), the 0.7 mg/g 17α-MT diet had the highest percentage. However, the hormone treatments had no serious effect on the survival rates of the fish in the study. The histopathological changes in the liver showed sinusoid dilation, vacuolization of hepatocytes, enlargement of central veins, and hemorrhages with increased hormone doses. In the kidney, treatment of 0.7 mg/g and 0.9 mg/g of the 17α-MT diet resulted in changes in the renal tubules, necrosis, degenerated kidney tubules, and dilation of the glomerulus. The present findings show that 17α-MT treatments notably enhance the overall length, weight, and general growth performance of O. niloticus. Therefore, carefully structured experiments employing suitable hormone doses in fish feed may prove advantageous for the commercial cultivation and conservation of this popular fish species in the country.

Phytoplankton of the littoral zone of Lake Baikal

Fedotov A.P., Domisheva V.M., Sakirko M.V., Vorobyeva S.S. — Wed, 26 Feb 2025 00:00:00 +0800

The study considers species composition, abundance, biomass of littoral phytoplankton of Lake Baikal in the spring (late May-early June) and autumn (late September) periods of 2017-2022. The study stations were located along the perimeter of the lake every 30-50 km. It characterises of the peculiarities of phytoplankton development in different areas of the lake and assesses the force of natural and anthropogenic factors on phytoplankton assemblage.

Application of polymeric amines as adjuvants to overcome resistance of Pseudomonas aeruginosa to tetracycline

Wed, 26 Feb 2025 00:00:00 +0800

Overcoming antibiotic resistance in pathogenic microorganisms is important due to the proliferation of initially resistant species whose resistance has increased over decades of antibiotic use. A significant danger is caused by Pseudomonas aeruginosa (Schroeter, 1872) Migula, 1900 (blue bacillus), which possesses a strong cell membrane and is capable of forming biofilms around colonies. We found that hydrophilic polyvinylamine, which does not contain any specific functional groups and binding centers, is able to significantly enhance the sensitivity of Ps. aeruginosa to tetracycline. The minimum inhibitory concentration was 0.26-1.16 μg/mL depending on the density of the initial culture of Ps. aeruginosa, which corresponds to the values for sensitive microorganisms.