Environmental impacts of physical and dynamical characteristics of the southern coastal waters of the Caspian Sea

2021 ◽  
pp. 1-14
Author(s):  
Siamak JAMSHIDI ◽  
Mahdieh JAFARI
Keyword(s):  
Water Column ◽  
Caspian Sea ◽  
General Circulation ◽  
Middle Part ◽  
Marine Debris ◽  
The Caspian Sea ◽  
Seasonal Thermocline ◽  
Field Samples ◽  
Current Characteristics ◽  
Coastal Flow

ABSTRACT This research evaluated the variability of current characteristics and seawater properties in the middle part of the southern shelf of the Caspian Sea. The effect of the coastal flow on marine debris dispreading was assessed in the southern Caspian Sea for the first time. The findings showed the existence of thermal stratification containing seasonal thermocline with thickness of about 40 m in the water column. Maximum monthly along-shore current velocities around 1.3 m s−1 were observed in November and December. Monthly variations were clearly found in both flow velocity and local wind components. However, no significant levels of correlation between wind and current speeds were observed during the study in the region. In some cases, the mean monthly cross-shore component velocities were measured at about 29 cm s−1 in November. The findings indicated that there was no upwelling phenomenon associated to the regional wind in the study area. In situ current measurements indicated dominant east and north-northeast directions, presumably related to the effect of general circulation in the southern basin. Current profiles in the water column displayed similarity in directions at 10, 15 and 20 m depths over the continental shelf. The field samples and analysis revealed that the soft and smaller-scale seawater litters can be carried long distances by the current along the coast. Most coastal based and marine litters originated from the tourist activities (in the middle and western parts of the shores) and waste emanated from the river (Tonekabon-Nowshahr).

scholarly journals Current State of Heterotrophic Bacterioplankton and Bacteriobenthos in the Northern and Middle Parts of the Caspian Sea

2020 ◽  
Author(s):  
Svetlana Dyakova ◽  
Victoria Volodina ◽  
Ekaterina Galyautdinova ◽  
Anna Menkova ◽  
Olga Soprunova
Keyword(s):  
Species Composition ◽  
Crude Oil ◽  
Bottom Sediments ◽  
Caspian Sea ◽  
Heterotrophic Bacteria ◽  
Middle Part ◽  
The Caspian Sea ◽  
Heterotrophic Bacterioplankton ◽  
Fermenting Bacteria ◽  
Two Peaks

Data on the abundance of heterotrophic bacterioplankton and bacteriobenthos in the northern and middle parts of the Caspian during the period from 2013 to 2017 are presented. In the waters of the northern part of the Caspian, a peak in the number of saprotrophs and crude oil degraders was recorded in 2013. In the middle part of the Caspian and in the region of the Mangyshlak regression, high numbers of heterotrophic bacteria were recorded in 2013 and 2016. The biodiversity of bacterioplankton in the surveyed areas is almost the same; the species composition of saprotrophs and crude oil degraders is identical. In the bottom sediments of the northern and middle parts of the Caspian Sea, two peaks of saprotrophic bacteriobenthos development (in 2013 and 2016) were recorded; in the region of the Mangyshlak threshold, the concentration of saprotrophs remained stable. The number of crude oil degraders was inferior to those of saprotrophs, while the proportion of crude oil degraders to saprotrophs changed annually. The species composition of saprotrophs is relatively stable, the biodiversity of oil-oxidizing bacteriobenthos has changed in the direction of increasing the proportion of non-fermenting bacteria. Constant changes in the ratio of the number of saprotrophs and crude oil degraders, together with the transformations of the dominant groups of the species composition of bacteria, indicated the instability of bacteriobenthos, and, as a result, the vulnerability of the microecosystem of bottom sediments under changing environmental conditions.

scholarly journals Temporal variability of catches, distribution and dynamics of length of Russian sturgeon in waters of the Caspian Sea in 2015 –2020

2021 ◽  
Vol 0 (4) ◽  
pp. 80-90
Author(s):  
Irina Victorovna Konopleva
Keyword(s):  
Caspian Sea ◽  
Adult Population ◽  
Water Layer ◽  
Middle Part ◽  
Russian Sturgeon ◽  
The Caspian Sea ◽  
Bottom Water Layer ◽  
The North ◽  
Shallow Zone ◽  
Heating Up

The paper presents long-term data on catches, distribution and length dynamics of Russian sturgeon in the waters of the Caspian Sea for the summer-autumn periods in 2015-2020. When considering the catches in the different parts of the sea there is found their annual variability, which is especially noticeable in the shallow zone in the North Caspian (0.31-2.0 specimens/trawl) and in the Middle Caspian (0-1.31 specimens/trawl). In the course of determining the reasons for the interannual dynamics of catches there were revealed several decadal rises. The dependence of decadal catches on the temperature of the bottom water layer was analyzed. The highest rise in catches was observed in the first decade of September when the temperature of water lowered up to 20.0-15.0 °C. The increase was observed due to migrating individuals to the shallow zone of the Northern Caspian Sea from shallow waters. Despite the variability of catches, the localization of Russian sturgeon schooling in the northern and middle part of the sea during the summer-autumn periods of 2015-2020 has certain similar features and trends. Sturgeon species fed mainly on shallow banks and deep dumps, where the largest catches of sturgeon were recorded from 5.0 to 12.0 specimens/trawl. The absence of sturgeon at depths of up to 3.0 m isobath in the last five years is due to the water heating up to 27.6-28.8 °C. The decrease in the length of the Russian sturgeon observed in recent years is due to an increase in the proportion of youngsters (19.2-70.0%) against the background of a decrease in the adult population. It should be noted that from 2017 to 2019 there were not found the adult species in the catches by fishing nets, which indicates their continued re-moval from the population.

scholarly journals THE DISTRIBUTION OF DISSOLVED FORMS COPPER IN THE WATER COLUMN OF THE CASPIAN SEA

2018 ◽  
Author(s):  
В.В. Ковалев ◽  
С.Г. Парада
Keyword(s):  
Surface Layer ◽  
Spatial Distribution ◽  
Water Column ◽  
Caspian Sea ◽  
Sea Water ◽  
Average Content ◽  
Vital Activity ◽  
The Caspian Sea ◽  
Organic Complexes ◽  
High Concentrations

По результатам химических анализов проб воды Северного, Среднего Каспия и, частично, Южного Каспия, отобранных по профилям из различных горизонтов водной толщи, определены содержания растворенных форм меди. Построены карты пространственного распределения этого элемента в поверхностном и наддонном водных горизонтах, а также по вертикальным разрезам водной толщи, выявлены закономерности их распространения в объеме морской воды. Установлены средние содержания растворенных форм меди в поверхностном (8,6 мкг/л) и в наддонном (9,6 мкг/л) горизонтах  Каспийского моря. Выделены участки с аномально высокими (более 20 мкг/л) и аномально низкими (менее 5 мкг/л) концентрациями растворенных форм меди в них. Особенности распределения растворенных форм меди по вертикали водной толщи определяются жизнедеятельностью планктонных организмов и их отмиранием. В поверхностном слое аномально высокие концентрации меди связаны с прижизненным накоплением металла планктоном. На глубинах свыше 100 м аномально высокие ее концентрации связаны с распадом отмерших организмов и выделением меди и других металлов в виде органических комплексов According to the results of chemical analyzes of water samples from the Northern, Middle Caspian and, partially, the Southern Caspian, taken from profiles from different horizons of the water column, the contents of dissolved forms of copper were determined. Maps of the spatial distribution of this element in the surface and supra-aquatic horizons, as well as along vertical sections of the water column, have been constructed, and patterns of their distribution in the volume of sea water have been revealed. The average content of dissolved forms of copper in the surface (8.6 μg/l) and in the above bottom (9.6 μg/l) horizons of the Caspian Sea has been established. Selected areas with abnormally high (more than 20 μg/l) and abnormally low (less than 5 μg/l) concentrations of dissolved forms of copper in them. The specific features of the distribution of dissolved forms of copper along the vertical of the water column are determined by the vital activity of planktonic organisms and their death. In the surface layer, abnormally high concentrations of copper are associated with the lifetime accumulation of metal by plankton. At depths above 100 m, its abnormally high concentrations are associated with the decay of dead organisms and the release of copper and other metals in the form of organic complexes

scholarly journals FEATURES OF BEHAVIOR OF ORDINARY SPRAT (BY RESULTS OF HYDROACOUSTIC RESEARCHES)

2018 ◽  
pp. 65-73
Author(s):  
Igor Borisovich Balchenkov ◽  
Tatiana Vasilievna Pomogaeva
Keyword(s):  
Caspian Sea ◽  
Water Area ◽  
Early Spring ◽  
Middle Part ◽  
Summer Period ◽  
The Caspian Sea ◽  
Research Ship ◽  
Study Results ◽  
Seasonal Aspect ◽  
Made In

Caspian sprats are reserve target species. The study of species identification of Caspian sprats was carried out on board a research ship “Researcher of the Caspian Sea” using EK-60 hydroacoustic complex having stationary antennas with a split beam of 38 and 120 kHz. The behavior and distribution of ordinary sprats in the western part of the Caspian Sea (Middle part of the Caspian Sea off the coast of Dagestan) was investigated. Echo recordings of hydroacoustic surveys made in 2011-2017 covering the water area with depths from 20 to 300 meters were considered. A database with hydroacoustic research files was created, containing the parameters of the surveys and the graphic display of the echograms. Taking into account the negative reaction of ordinary sprat to light, both day and night recordings were considered. Characteristic echoes of ordinary sprat are described in the seasonal aspect. These studies, describing the nature of the behavior of ordinary sprats, are important for the organization of fishing in the western part of the Caspian Sea. It has been stated that density of sprat shoals during spring-summer period is not high, fishing by bottom trawl is efficient only at the end of August. The most promising sprat accumulations can be found in early spring (March) and in October and November, when sprat is caught in the industrial scale. The study results describing special behavior of ordinary sprats can be used in organizing sprat fishing in the Western part of the Caspian Sea.

scholarly journals Long-Term Evolution of the Caspian Sea Thermohaline Properties Reconstructed in an Eddy-Resolving OGCM

2018 ◽  
Author(s):  
Gleb S. Dyakonov ◽  
Rashit A. Ibrayev
Keyword(s):  
Caspian Sea ◽  
General Circulation ◽  
Decadal Variability ◽  
Global Climate ◽  
Circulation Model ◽  
Ocean General Circulation Model ◽  
Atmospheric Conditions ◽  
The Caspian Sea ◽  
Error Accumulation

Abstract. The decadal variability of the Caspian Sea thermohaline properties is investigated by means of a high-resolution ocean general circulation model including sea ice thermodynamics and air-sea interaction, forced by prescribed realistic atmospheric conditions and riverine runoff. The model describes synoptic, seasonal and climatic variations of the sea thermohaline structure, water balance and level height. A reconstruction experiment was conducted for the period of 1961–2001, covering a major regime shift in the global climate of 1976–1978, which allows to investigate the Caspian Sea response to such significant episodes of climate change. The long-term trends in the sea circulation patterns are considered with an assessment of the influence of model error accumulation.

scholarly journals INTERSPECIFIC NUTRITIONAL RELATIONSHIP BETWEEN CLUPEONELLA ENGRAULIFORMIS AND CLUPEONELLA CASPIA IN THE CASPIAN SEA

2019 ◽  
pp. 13-19
Author(s):  
Anna Viktorovna Mikhajlova
Keyword(s):  
Fish Species ◽  
Caspian Sea ◽  
Food Preferences ◽  
Pelagic Fish ◽  
Middle Part ◽  
Aqueous Environment ◽  
The Caspian Sea ◽  
Commercial Fish ◽  
The North ◽  
Close Relationship

Vital activity of the Caspian ichthyofauna is mainly determined by aqueous environment with its multiple factors influencing the hydrobionts’ life cycle. It is well known that in the process of evaluating the stocks of commercial fish species it is necessary to take into account supplying them with food. Trophologic studies of mature species of Clupeonella Caspia and Clupeonella Engrauliformis in the Caspian Sea make a basis for a large number of works; however, the research of food preferences of these fish species is scarce. Clupeonella Caspia inhabits the north, middle and south parts of the Caspian Sea above the 60 m isobath. Clupeonella Engrauliformis is widespread in the middle and southern parts of the Caspian Sea above the depths more than 200 m. In the course of evaluating kilka fattening in the Caspian Sea that was continued in 2011 there were estimated nutrition relations of kilka species over the many years, traced the degree of nutritional similarity and registered interspecific relationship between these pelagic fish. The results obtained have been summarized and the whole range of trophic studies has been shown. The monitoring nature of the studies allows to infer the intensive feeding of Clupeonella Caspia and Clupeonella Engrauliformis in the summer of 2011-2014 and in 2016 in the middle part of the Caspian Sea (the study of pelagic fish fatting was not conducted in 2015). The multi-year comparative analysis of Clupeonella Caspia and Clupeonella Engrauliformis nutrition demonstrated the differences of using the dominant foodstuff among planktonic invertebrates. It has been stated that the index of similarity of the food spectrum does not always have a greater degree of coincidence in close relationship of fish in a systematic respect.

scholarly journals DISTRIBUTION OF CASPIAN SPRATS IN THE NORTH-WESTERN PART OF THE CASPIAN SEA (BASED ON RESULTS OF HYDROACOUSTIC RESEARCH IN NOVEMBER 2018)

2019 ◽  
pp. 41-50
Author(s):  
Tatiana Vasilievna Pomogaeva
Keyword(s):  
Caspian Sea ◽  
Water Surface ◽  
Bottom Layer ◽  
Water Area ◽  
Middle Part ◽  
Average Density ◽  
Layer By Layer ◽  
The Caspian Sea ◽  
The North ◽  
Study Results

Since Caspian sprat today is a reserve fishery object, hydroacoustic studies are the main purpose of solving the problem of estimating concentrations, areas and terms of the organization of the Russian marine fishery. A promising fishing area is the region of the middle part of the Caspian Sea, off the Dagestan coast, which has been studied since 2011. As it was found during previous studies, the densest sprat schools form in the autumn period in the bottom layer. The present research focuses on Caspian sprat distribution in the western part of the Middle Caspian in November 2018. Hydroacoustic tacks covered a water area of 630 NM. The echo recordings of hydroacoustic surveys covering the water area at the depths 20-60 m were analyzed. The recordings were studied considering the response of sprat to the day and night light. Processing of hydroacoustic data was carried out in several stages: analytical viewing of echograms purposed to identify specific features of sprat; recording minimum and maximum values of echo intensity depending on the depth; data post-processing in SIMRAD BI-60 program. The distribution of Caspian sprats is represented totally from the water surface to the ground, and layer by layer, in layers of 10 meters from the water surface. It has been stated that in the surface layer there are practically no sprat schools. The maximum value of the average density (8.7 t / mile2) was registered in the bottom layer (40-50 m). The study results can be used in organization of Russian sprats fishing in the Caspian Sea.

Biogeochemical processes in the water column of the Caspian Sea in November 2008

2010 ◽  
Vol 434 (2) ◽  
pp. 1381-1385 ◽  
Author(s):  
A. Yu. Lein ◽  
I. I. Rusanov ◽  
A. A. Klyuvitkin ◽  
M. D. Kravchishina ◽  
E. E. Zakharova ◽  
...  
Keyword(s):  
Water Column ◽  
Caspian Sea ◽  
Biogeochemical Processes ◽  
The Caspian Sea
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