In the course of the research, the biological features of the accumulation of
microelements by the organs and tissues of the Persian sturgeon in comparison
with the Russian, as well as the regularities of the age accumulation of sturgeon
were revealed. Studies of the elemental composition of organs and tissues of the
Persian (Acipenser persicus, Borodin, 1897) and Russian (Acipenser gueldenstaedtii,
Brandt, 1833) sturgeon revealed a number of specific features associated with
different rates of metabolic processes in fish: the level of iron, copper, manganese,
zinc, and mercury in the Persian sturgeon (Acipenser persicus) in almost all organs
and tissues, it was recorded higher than in the Russian, at the same time, the
content of cadmium and cobalt indicates its greater accumulation in the organs
and tissues of the Russian sturgeon (Acipenser gueldenstaedtii).
Until the end of the XX century, anchovy sprat was the leading object of marine fishing in the Caspian Sea. At the beginning of the XXI century, there was a mass death of this species, as well as an outbreak of the number of mnemiopsis comb - a powerful consumer of feed zooplankton. There was a redistribution of keel clusters in the sea. The main part of the fishing stock of keels began to be distributed in the Middle Caspian Sea. The main object of marine fishing has become an ordinary sprat. In recent years (2015-2020), there has been an increase in the number of anchovy sprats. The materials of keel surveys also confirm the annual growth in the number of juvenile sprats. This paper presents the results of recent years of observations, shows the dynamics of the number and biomass of the population, the parent part of the herd, total fertility. The efficiency of spawning and the survival coefficients of the generation in early ontogenesis are shown. Environmental factors that have a direct impact on the formation of the anchovy sprat stock are described.
Aim. Reveal the distribution of cadmium in the components of the ecosystem of the Caspian Sea. Materials and Methods. The sampling was carried out according to generally accepted methods, the determination of heavy metals was carried out by the method of atomic absorption spectroscopy using an atomic absorption spectrometer with electrothermal atomization MGA-915 MD.Results. As a result of the studies carried out, it was found that the bottom sediments of the Middle Caspian were distinguished by a greater accumulation of cadmium than the North Caspian. Invertebrates of the Caspian Sea accumulate cadmium from water and soil, with the exception of shrimp, for which water is the only source of metal. Among the taxonomic groups of organisms studied, molluscs of the genus Didacna are cadmium accumulators. In the body of the Russian and Persian sturgeons, cadmium is mainly accumulated in the kidneys.
Conclusion.Coefficients of cadmium accumulation in the organs and tissues of Russian and Persian sturgeons, black-backed herring and Dolginsky herring relative to their food objects indicate that cadmium is able to accumulate in food chains.
The main sources of chemical elements for aquatic organisms are sea water and bottom sediments, and the levels of chemical elements in organisms depend on the level of these elements in the environment. The Caspian Sea is a special biogeochemical province with geochemical barriers in the area of mixing of river and sea waters, therefore, the study of its biogeochemical background, the peculiarities of the chemical composition of bottom sediments is the relevance of the work. The aim of this work was to reveal the content of manganese and copper in the bottom sediments of the Caspian Sea. The study revealed low concentrations of copper and relatively high manganese in the bottom sediments of the Caspian Sea, which is primarily due to the parent rocks of the Caspian lowland, which are poor in Cu, but rich in Mn. The results of biogeochemical analysis of bottom sediments of the ecosystem of the Caspian Sea serve as material for resolving the issue of the role of biogenic transformation of microelements in the cycle of substances.
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