Browsing Aquatic Bioresources & Environment, Vol. 4, No 3, 2021 by Title
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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)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.
Pesticides of modern classes in the water and bottom sediments of the Don RiverThe 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.
Phytoplankton variables dynamics in the Halda River (Bangabandhu Fisheries Heritage), Chittagong, BangladeshThe 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)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.