• 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.
    • 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.