Limnology and Freshwater Biology

Breeding biology, morphometric relationships and condition Factor of Lepidocephalichthys guntea (Hamilton, 1822)

2024-09-10T01:56:06+08:00

Lepidocephalichthys guntea, commonly known as loach, is a popular freshwater fish found in various water bodies. This study collected 210 specimens (148 females, 62 males) from fish markets in Noakhali, Bangladesh, to measure various length, weight, gonado-somatic index (GSI), fecundity and condition factor. To establish correlations, the relationships between length-length, length-weight, and GSI with both length and weight were analyzed. Body weight ranged from 1.99 to 8.89 g (mean 4.21 ± 1.49 g), and total length from 6.5 to 10.3 cm (mean 7.91 ± 0.77 cm). GSI peaked in June (8.63±1.16%), followed by May (6.58±0.89%), with the lowest values in September (0.01%). Mean fecundity was 7415.3±1168.54 in May and June (spawning season). The condition factor (K_F) was highest (1.04) in fish between 9.5–10.4 cm and lowest (0.87) in the 7.5–8.4 cm group. The coefficient of correlation (r²) values showed a strong positive relationship between body weight (BW) and both total length (TL) and standard length (SL). Moderate positive correlations were found between BW and head length (HL), and BW and body circumferences (BD) in pooled and female samples. However, in male, the correlations for BW vs. HL, BW vs. BD, as well as TL vs. HL and TL vs. BD, were asymmetrical. The relationships between GSI and both BW and gonad weight (GW) showed moderate positive correlations. Conversely, the coefficient of correlation between GSI and TL in the pooled sample, and GSI with both TL and BW in males, were indicating weak correlations. This study will provide valuable insights for conservation policymakers and hatchery owners, aiding in efforts to prevent the extinction of this species in the wild.

First finding of nematode DNA of the genus Rhabdochona (Spiruromorpha: Thelazioidea: Rhabdochonidae) in the metagenome of the digestive tract of a deep-water species: Godlewski’s sculpin Abyssocottus (Limnocottus) godlewskii

2024-09-25T17:02:31+08:00

Nucleotide sequences of the fragment of the cox1 gene in nematodes with the relative DNA representativeness of 2.6% were identified for the first time by the method of high-throughput sequencing in the digestive tract of Godlewski’s sculpin Abyssocottus (Limnocottus) godlewskii. The phylogenetic analysis performed allowed to state that the sequences obtained belong to a representative of the family Rhabdochonidae (Spiruromorpha: Thelazioidea). Representatives of Rhabdochonidae have not been found yet in the parasitic fauna of Lake Baikal sculpins. Possible ways of nematode DNA income into the digestive tract of fish are discussed.

Assessment of thermal characteristics of lakes in the permafrost zone by mathematical modelling (on the example of lakes in Yakutia)

2024-07-23T03:11:31+08:00

The purpose of the study is to identify the possibilities of mathematical modeling in solving problems of quantitative assessment and prediction of hydrothermodynamic characteristics of lakes of different origins in the permafrost zone based on available information about their morphometry. The object of the study is 420 of morphometrically studied lakes in Yakutia of different genetic origin. The choice of an adequate hydrothermodynamic model of processes in the “atmosphere – lake – bottom sediments” system, as well as sources of information on the atmospheric impact on lakes (reanalysis and climate prediction) for the studied region was substantiated. Simulation calculations were carried out to assess the retrospective interannual and intraannual dynamics of abiotic processes in water and bottom sediments of lakes located in the permafrost zone of different climatic regions of Yakutia. To assess the interannual dynamics of the studied processes in water and bottom sediments of thermokarst lakes located in permafrost zones and being the most widespread in the region, forecast calculations were carried out. In this case, two RCP scenarios for the evolution of anthropogenic greenhouse gas emissions into the atmosphere in the future were used – “best” and “worst” in terms of environmental impact. The prospects for further use of modeling methods in the creation of a system of remote monitoring of unstudied and poorly studied lakes in the Arctic regions of the Russian Federation was assessed.

Problems of quality assessment of highly colored water of Lake Onego urbanized tributary using hydrochemical, microbiological and toxicological indicators

2024-07-10T17:35:50+08:00

The article presents the results for 2014–2015 of chemical, microbiological and toxicological studies of the water quality of the urbanized tributary of Lake Onego (the River Neglinka). The high anthropogenic load on the studied river was revealed. The runoff of storm water reached one third of the river runoff. The maximum excess of maximum available concentration in storm water for BOD₅ was 80–90-fold, for oil products – 50–60-fold, for suspended solids – 40-fold. The River Neglinka in the upper reaches (outside the urban area) is affected by a swampy catchment area. The chemical composition of the water (low pH values, high color index, COD_Cr and Fe_tot) reflected the influence of catchment area. The methodological problems were associated with identifying zones of anthropogenic impact against the background of the negative impact of natural factors on the water quality of the River Neglinka. In the calculation a modified specific combined water contamination index was used. This made it possible to determine zones of influence of the anthropogenic factor. Microbiological indicators (total bacterial abundant, total coliform bacteria, saprophytic bacteria) indicated a high degree of pollution of the River Neglinka and especially sanitary-indicative bacteria. The unsuitability of the River Neglinka for recreational use was revealed. Bioassay revealed the toxicity of the river water in the upper reaches. It was connected with the low pH due runoff of humic substances from swampy catchment area. The barrier role of groundwater, which led to an increase in the pH, and the complexing ability of humic substances, which reduced the bioavailability of heavy metals, stipulated non toxicity river water in urban areas. The study proved that the assessment of the quality of highly colored river waters is possible only with a comprehensive implementation of chemical, microbiological and toxicological studies.

Comparing the efficiency of two water sampling methods for studying the content of microplastics in water bodies

2024-06-25T19:13:18+08:00

Due to the lack of a unified sampling methodology for studying microplastics, there are difficulties in comparing the results obtained when sampling using different methods. A comparison was made of a pump filtration system and a Manta trawl to assess their effectiveness and applicability in collecting water samples for studying microplastics content using the example of Lake Ladoga, the Svir River and small lakes in the Leningrad region (Sukhodolskoye, Michurinskoye, Krasnoye). The results supported that despite higher average microplastics concentrations when sampling with the pump system (8.5±11.5 particles/m³) compared to the Manta trawl (0.7±0.6 particles/m³), the data were comparable. The methods have opposite advantages and disadvantages and are complementary. The Manta trawl is more suitable for collecting large volumes of water from the surface layer relatively quickly and in conditions with high contents of suspended matter present. Meanwhile, the pump filtration system is suitable for collecting samples at different water layers and in the surface layer of water when there is a small content of suspended matter and provides more accurate estimating of the sample volume. It is necessary to ensure the sampling of a large volume of water, which in the case of a pump filtration system is only possible during the period when the plankton content and water turbidity are minimal.

“Diatoms: Life in Glass Houses” revisited: Updates and Comments

2024-12-25T11:55:22+08:00

The film “Diatoms: Life in Glass Houses”, produced in 2003, covers various aspects of this ecologically important class of algae, such as their occurrence, cell biology including cell division and reproduction, morphology, morphogenesis, motility, and the formation of colonies. The aim of this work is to review and comment on some of the aspects presented in the video in the light of current knowledge. Special attention will be given to the constraints imposed by the solid silica wall and how diatoms cope with them. No attempt is made to be comprehensive.

Genetic diversity of freshwater diatom algae populations Ulnaria danica (Kützing) Compère & Bukhtiyarova and Ulnaria ulna (Nitzsch) Compère

2024-11-11T14:41:39+08:00

Araphid diatoms of the genus Ulnaria are the dominant species in many freshwater ecosystems of Eurasia. Diatom populations are genetically heterogeneous and represent a combination of different genotypes. Genetic diversity is a necessary factor for adaptation to different environmental conditions and successful dispersal of species. We were analyzed the genetic diversity of the species Ulnaria danica and Ulnaria ulna using the example of monoclonal strains isolated from geographically distant water bodies of the continental part of Eurasia: Lake Ritsa, Lake Goluboe and Lake Baikal. Phylogenetic analysis of cox1 gene fragments of the studied strains demonstrated for the first time the heterogeneity of populations and the absence of geographic isolation for individual genotypes of the studied species. By analyzing the 18S rRNA marker genes, rbcL and cox1, the possibility of horizontal gene transfer between closely related species Fragilaria radians, Ulnaria acus, U. danica and U. ulna was established.

Hydroacoustic studies of macrozooplankton in Lake Baikal

2024-10-22T13:52:05+08:00

A hydroacoustic survey of the distribution of aggregations of Macrohectopus branickii (Amphipoda) in Barguzinsky Bay of Lake Baikal was conducted for the first time in the last 30 years. The hydroacoustic complex “Echo-Baikal” was used in the research. Verification of hydroacoustic data is based on the results of synchronous net catches with a JOM net. The present study demonstrates that macrohectopus aggregations are confined to slope zone areas with depths of 100–150 m. The dependence between the strength of the mean volume backscattering and the density of macrohectopus was obtained, based on which its biomass in Barguzinsky Bay was estimated at 2.7·10⁶ kg.

Changing the appearance of underwater landscapes in the coastal zone of a large freshwater body under the influence of trout farming activities: a case study of Mustalakhti Bay, Lake Ladoga

2024-09-18T13:48:41+08:00

In Mustalakhti Bay of Lake Ladoga, which is used for placing trout farms, a study was conducted on the structure of bottom landscapes and the transformation of the lakebed surface under the influence of aquaculture activities. Field data for mapping bottom landscapes were collected using hydroacoustic surveys with the SOLIX 10 SI MEGA CHIRP side-scan sonar and underwater photography with the Limnoscout ROV. Standard sedimentological and biological studies of the lakebed were also carried out. The identification of distinct facies elements was based on morphometric features (depth zones, bottom slopes in different parts of the bay, and terrain elements), characteristics of bottom sediments (sediment type, fluid mud composition), surface appearance, and benthic biological communities (dominant benthic groups, presence/absence of macrophytes). The study resulted in bathymetric and landscape maps of the investigated bay, highlighting the characteristic features of individual landscape facies. A total of 8 facies were identified. The study demonstrated a significant negative impact of trout farms on the bay’s bottom. This is confirmed by: 1. substantial changes in the lakebed appearance detected through video footage; 2. visual changes in the surface observed in acoustic images (sonograms) from the side-scan sonar; and 3. increased sediment thickness and higher accumulation of organic matter, evidenced by sonar data and previously conducted chemical analyses of sediments in the farm areas. The data indicates that the features of the bay’s basin, specifically its steep slopes and the extensive shallow area with relatively large depths (20-35 m), create conditions for the accumulation of anthropogenically transformed sediments within the farm area and extending outwards by several tens of metres (a 100 m diameter zone around each farm). Conclusion: The use of a landscape approach with modern research tools, including acoustic and underwater photography, has provided a spatial assessment of the impact of trout farming on the condition of the studied section of the freshwater body.

Peculiarities of the chemical composition of the snow cover in the northern basin of Lake Baikal

2024-11-25T01:19:09+08:00

This article presents the 2023 data on the snow cover in the northern basin of Lake Baikal. We estimated the spatial distribution of the main chemical elements in the snow cover. The high relative concentration of nitrates and hydrogen ions was a characteristic of the ionic composition of snowmelt water in comparison with the industrial areas of the Baikal region. We calculated the accumulation of major ions and biogenic elements in the snow cover. A comparative analysis of the obtained experimental data with regional background values and results of the similar previous studies revealed a trend towards a decrease in mineralization and an increase in the acidity of snow melt waters over the past 11 years. Low values of the total amount of ions and pH in the snow cover of some areas of the northern basin of Lake Baikal allowed us to classify them as a background for the entire Baikal region.

Investigation of applicability of different approaches to calculation of geostrophic currents on the example of under-ice eddies forming ice rings on Lake Baikal

2024-12-25T17:06:22+08:00

This work is devoted to the study of the spatial distribution of horizontal currents in subglacial anticyclonic eddies leading to the formation of ring structures on the spring ice of Lake Baikal. The horizontal fields of geostrophic currents were calculated using the dynamic method, with the main attention paid to the comparison of different approaches to the calculation of water density, including the TEOS-10 software package specially adapted for Baikal conditions. Measured water temperature and conductivity in the area of the ring structure in 2009 were used as input data. And as reference data - series of profiles of velocity and direction of currents in a similar vortex in 2020, measured for the first time. Comparisons showed that the use of outdated methods (such as the Krotova method or the Chen-Millero equation) leads to significant discrepancies with real measurements, while the adapted TEOS-10 package demonstrates the best agreement. In general, the dynamic approach proved to be valid and can be successfully applied to study the flow fields in Lake Baikal. In the course of the conducted studies, a number of characteristic features of the current structure in the investigated subglacial circulations were revealed and described for the first time.