• Phytoplankton variables dynamics in the Halda River (Bangabandhu Fisheries Heritage), Chittagong, Bangladesh

      Islam, Md.S. (2021)
      The Halda is a river ecosystem of major importance, well-suited for the natural spawning of major carps due to the unique physicochemical and biological properties of its water. The productivity of the Halda ecosystem mainly depends on the plankton density. The present study has been aimed at the determination of qualitative and quantitative density of the phytoplankton in the Halda River during a two-year period extending from January, 2017 to December, 2018. Phytoplankton density is a good indicator of the water quality of a river ecosystem. A total of 74 species of phytoplankton divided into 47 genera belonging to 6 phyla has been recorded. Bacillariophyta was the most dominant phylum of phytoplankton followed by Cyanobacteria, Chlorophyta, Miozoa, Charophyta, and Euglenozoa. The maximum phytoplankton density was recorded during the pre-monsoon period, and its minimum fell upon the post-monsoon period. The phytoplankton showed a positive significant relationship with transparency, total dissolved solids, conductivity, calcium, total hardness, and BOD5 and an inverse significant relationship with water temperature. The water of the Halda River is organically polluted and eutrophic in its nature.
    • Shoal-water macrozoobenthos of the south-eastern part of the Karkinit Bay (Black Sea)

      Kopiy, V.G.; Bondarenko, L.V. (2021)
      This work is based on the data collected during the benthic survey of soft sediments along the coastal zone of the south-eastern part of the Karkinit Bay in August, 2018. The current condition of the macrozoobenthos relating to the changes occurring in the bay area after the termination of the North- Crimean Canal’s operation has been analyzed. The samples were collected using a manual box-corer with a capture area of 0.04 m2 at the depths from 0 to 1 m. The depth of the captured surface soil layer was 5–7 cm. The following indices have been used to describe the quantitative development of the benthos: abundance, biomass, occurrence, density index, and the Chekanovsky–Sørensen similarity coefficient. In total, 15 species of polychaetes, 19 species of crustaceans, 5 species of Mollusca and unidentified species of Oligochaeta, Chironomidae, Nemertea, Turbellaria and Actiniaria have been found. The average values of macrozoobenthos abund ance and bioma ss in the investigated area were 3,131±2,031 ind./m2 and 24.66±16.93 g/m2, respectively. The largest number of species has been recorded within the water area of “Swan Islands” natural reserve. The trophic structure of the macrozoobenthos is represented by poly-, phyto-, detrito- and carnivorous animals. A high similarity level of faunas has been registered between the mouth and the inner part of the Krasnoperekopsk Bay. Following the analysis of the macrozoobenthos status in 2008 and 2018, changes in prevalence of certain taxonomic groups and abundant species of the macrozoobenthos have been identified.
    • Pesticides of modern classes in the water and bottom sediments of the Don River

      Valiullin, V.A.; Zinchuk, O.A.; Karpushina, Yu.E. (2021)
      The Don River in the Rostov Region is almost entirely surrounded by agricultural land, where the use of chemical plant protection products is an integral part of the production cycle. By transferring with the air masses or seeping through the soil, pesticides can enter the water of the water bodies of fisheries importance, be deposited in bottom sediments, and negatively affect the vital activity of hydrobionts. The aim of the study was to detect in the habitat of hydrobionts (water and bottom sediments) of the Don River the content of 20 active ingredients of the pesticides of modern classes most widely used in agriculture in the region, the half-life of which can exceed six months. The study was conducted by high-performance liquid chromatography (HPLC). To prepare for chromatography, the extraction of pesticide active ingredients from the samples of water and bottom sediments was performed using dichloromethane, followed by drying with anhydrous sodium sulfate and purification of extracts using solid-phase extraction cartridges (if necessary). The identification of the active ingredients of pesticides was carried out by the retention time, and the quantitative determination was carried out by the method of absolute calibration. Standard samples of pesticide active ingredients were provided by Bayer AG. It was found that the concentrations of pesticide active ingredients in the living environment of hydrobionts in the Don River are by more than an order of magnitude lower than the established maximum allowable concentrations (MAC), which indicates the relative safety of the environment for hydrobionts.
    • On the joint influence of body size and water temperature on the growth rate of the Pacific oyster (Сrassostrea gigas, Thunberg) in the Donuzlav Liman (Black Sea)

      Zolotnitskiy, A.P.; Orlenko, A.N. (2021)
      The Pacific oyster (Сrassostrea gigas, Thunberg) is a cultivated species of a world-wide importance, which results in the relevance of the investigation of its growth rates in various areas of the World Ocean. This parameter defines the time needed for an individual to reach its commercial size and characterizes cost-effectiveness of cultivation of different species of hydrobionts. Within this context, it is essential to investigate not only the general regularities and patterns of the Pacific oyster’s growth, but also how it is influenced by other environmental factors. In this work, the joint influence of body size and water temperature on the linear growth of diploid individuals of the Pacific oyster in the Donuzlav Liman (Black Sea) is investigated. Quantitative characterization of the relationship between shell height (H, mm) and the age of a mollusc (t), which is similarly well described by the von Bertalanffy equation and power function, is presented. Analysis of the changes in absolute growth rate (Ph, mm/day) in dependence to body height (H, mm) and water temperature (T, °С) has been conducted. It is shown that the growth rate of oysters was steadily decreasing with their height gain, all the while seasonal changes in water temperature (T, °С) closely correlated with the absolute growth rate of a shell and were characterized by a positive relation. Following the available data, a mathematical model, where Ph can be presented as a function of two variables, water temperature and body size, is proposed; it is expressed by the equation. The presented model of multiple regression has adequately described the dynamics of Ph (coefficient of determination 0.71) in the course of 3-year rearing of the Pacific oyster. Observed deviations (0.29) have been associated with the early stages of ontogenesis and with reproduction processes of this species.
    • The influence of abiotic and anthropogenic factors on the formation of the present composition of the ichthyofauna in the Chogray Reservoir

      Karnaukhov, G.I.; Kashirin, A.V.; Gitalov, E.I.; Sirota, Yu.V. (2021)
      Following the results of long-term investigation of the Chogray Reservoir, carried out in the period from 2010 to 2020, the data on its hydrological and hydrochemical regime and the current composition of its ichthyofauna are presented. The ichthyological material has been collected and processed according to generally accepted methods. The stocks and abundance have been calculated using the method of direct counting per area unit. The results of this investigation indicated that the formation of the species composition of fish in the reservoir was influenced by biotic and abiotic factors and passed several stages. At the first stages of the formation of the ichthyofauna of the Chogray Reservoir, common carp, Prussian carp and zander prevailed in its species composition. The basis of the ichthyocenosis of the Chogray Reservoir was and proceeds to be composed of demersal species. In 1972, the acclimatization of common bream was carried out. In the first years of commercial exploitation of the reservoir, the main fishing target was carp, which by the early 1980s began to be replaced by common bream. The main commercial fish species in the Chogray Reservoir are the following, in order of their abundance: common bream, European perch, Prussian carp, common roach, common carp, and white bream. It is established that in the last years of operation of the reservoir, the fish community has undergone certain changes that are associated with hydrological and hydrochemical fluctuations. Currently, the biodiversity of the ichthyofauna is represented by 22 species and subspecies of fish. The percentage for species distribution of commercial fish species in the ichthyofauna of the Chogray Reservoir is presented (in 2020, the share of common bream was 56 %, and Prussian carp and European perch accounted for 14 % each). The reduction in the exploitable volume of water in the reservoir led to an increase in the area of shallow waters, their overgrowth, a reduction in the stocks of the main commercial fish species and an increase in the population of tench. The average water salinity increased from 1.9 to 2.7 g/L. During the commercial exploitation of the reservoir, significant fluctuations in catches were recorded.
    • Dynamics of mussel and mytilaster settlements on the hydraulic structures of recreational waters

      Solovieva, O.V. (2021)
      In the coastal waters, hydraulic structures form additional areas for the development of the fouling community. In recent years, Mytilidae fouling of the solid substrates in the Crimean coastal waters undergoes a transformation. These phenomena cause a change in the natural biofilters aggregated on the surface of hydraulic structures and, as a result, a change in the self-cleaning capacity of the water areas. This work is aimed at the assessment of the inter-annual dynamics of the settlements of Mytilus galloprovincialis Lam. and Mytilaster lineatus Gmel. and the assessment of the capacity of the biofilter formed by Mytilidae molluscs on hydraulic structures in recreational waters during the beach season. On average, for the period from 2015 to 2018, the mussel abundance at the investigated structures decreased from 1,125±523 to 462±221 ind./m2. The biomass of this species decreased from 893±397 to 462± 221 g/m2. The length frequency in the mussel settlements has not changed. For certain areas, the characteristics of the length composition identified earlier have been preserved. A significant decrease in the abundance and biomass of mytilasters was recorded for 2015–2018. The abundance of these molluscs decreased from 33,443±11,084 to 1,094±228 ind./m2. The biomass of the investigated species decreased from 2,492±1,165 to 1,099±332 g/m2. The length composition of the mytilaster for the period of this investigation remained relatively unchanged. As a result of the decline in the settlement density and biomass of Mytilidae molluscs, the volumes of the water filtered by the molluscs were significantly lower in 2018 than in 2015. For mussels, the average value was 4,640±4,123 L/day·m2 in 2018, which is almost 4 times lower than the said value in 2015. In 2018, this value for mytilaters was, on average, 10,256±3,875 L/day·m2. Thus, the decrease in the total performance of the natural biofilter on the hydraulic structures in the recreational waters of Sevastopol and, as a result, the reduction in the self-cleaning capacity of these waters have been recorded.
    • Characterization of the zooplankton community in the cooling pond of the Rostov Nuclear Power Plant

      Shlyakhova, N.A. (2021)
      This research was aimed at the investigation of the impact exerted by the waters, heated after passing through the Rostov NPP power units, on quantitative and qualitative characteristics of the zooplankton both in spatial and temporal terms and on its distribution over the water body area in relation to the degree of artificial heating. The data were collected in the spring, summer and autumn seasons of 2019 in the areas of high and medium heating, as well as the ones influenced by the Tsimlyansk Reservoir waters, and in the head and tail races. The planktonic fauna was represented by 30 species. The main components of the zooplankton community were the members of the Brachionus (Pallas, 1766) and Keratella Bory de St. Vincent, 1822 genera for rotifers, Diaphanosoma brachyurum (Liévin, 1848) for cladocerans, brackishwater Eurytemora affinis (Poppe, 1880) and small thermophilic species of Mesocyclops Sars, 1863 and Microcyclops Claus, 1893 genera for copepods. The area influenced by Tsimlyansk Reservoir waters was characterized by the highest values of quantitative parameters of zooplankters; their abundance and biomass were 53,493 ind./m3 and 287.9 mg/m3, respectively. The lowest values of quantitative parameters have been registered in the tail race of the RoNPP; the abundance equaled 1,826 ind./m3, and the biomass was 13.6 mg/m3. On average, during the growing season, the zooplankton abundance in the cooling pond in general was 27,853 ind./m3, with its biomass being 97.7 mg/m3, while in the tail race those values amounted to 5,267 ind./m3 and 25.0 mg/m3, respectively. Despite an increased background temperature and a significant decrease in the quantitative parameters in the tail race, the zooplankton community of the cooling pond was characterized by rich species composition and regular seasonal dynamics of quantitative parameters, which is typical for the water bodies in Southern Russia. The results of this investigation indicate a slight impact of the heated waters on the zooplankton community in the cooling pond of the RoNPP.
    • Hydrochemical and hydrobiological characteristics of the lakes of the Shchuchinskо-Borovsk resort zone (Northern Kazakhstan) and the main methodological approaches to assessing the ecological state of small water bodies

      The book is a result of an international project on cooperation between Kazakhstan and Israel. The monograph includes data on hydrochemistry and hydrobiology of six lakes in the Shchuchinsko- Borovsk resort zone (Northern Kazakhstan). It provides information on the current state, interannual changes and the spatial distribution of chemical parameters and the structure of phytoplankton and zooplankton communities. A comprehensive assessment of the ecological state of lakes is given on the basis of chemical and biological indicators. Methods and problems associated with assessing the health of aquatic ecosystems are discussed. It also provides the systematic understanding of the diversity of planktonic algae and invertebrates.