The Caspian Sea flows into the black. Caspian Sea (largest lake)
Caspian Sea- most big lake on Earth, located at the junction of Europe and Asia, called the sea because of its size. Caspian Sea represents drainless lake, and the water in it is salty, from 0.05% near the mouth of the Volga to from 11-13% in the southeast.
The water level is subject to fluctuations, at present - about 28 m below the level of the World Ocean.
Square Caspian Sea currently - approximately 371,000 sq. km, maximum depth- 1025 m.
Length coastline Caspian Sea estimated at about 6500 - 6700 kilometers, with the islands - up to 7000 kilometers. coast Caspian Sea in most of its territory - low-lying and smooth. In the northern part, the coastline is indented by water channels and islands of the Volga and Ural deltas, the shores are low and swampy, and the water surface is covered with thickets in many places. On east coast limestone coasts adjoining semi-deserts and deserts predominate. The most winding coasts are on the west coast in the area of the Apsheron Peninsula and on the east coast in the area of the Kazakh Gulf and Kara-Bogaz-Gol.
IN Caspian Sea 130 rivers flow into it, of which 9 rivers have a mouth in the form of a delta. major rivers flowing into the Caspian Sea - Volga, Terek (Russia), Ural, Emba (Kazakhstan), Kura (Azerbaijan), Samur (Russian border with Azerbaijan), Atrek (Turkmenistan) and others.
Map of the Caspian Sea
The Caspian Sea washes the shores of five coastal states:
Russia (Dagestan, Kalmykia and Astrakhan region) - in the west and north-west, the length of the coastline is 695 kilometers
Kazakhstan - in the north, northeast and east, the length of the coastline is 2320 kilometers
Turkmenistan - in the southeast, the length of the coastline is 1200 kilometers
Iran - in the south, the length of the coastline - 724 kilometers
Azerbaijan - in the southwest, the length of the coastline is 955 kilometers
Water temperature
is subject to significant latitudinal changes, most pronounced in winter, when the temperature varies from 0 - 0.5 °C at the ice edge in the north of the sea to 10 - 11 °C in the south, that is, the water temperature difference is about 10 °C. For shallow water areas with depths less than 25 m, the annual amplitude can reach 25 - 26 °C. The average water temperature at west coast 1 - 2 °C higher than that of the eastern, and in the open sea the water temperature is 2 - 4 °C higher than that of the coasts.
Climate of the Caspian Sea- continental in the northern part, temperate in the middle part and subtropical in the southern part. In winter average monthly temperature The Caspian varies from -8 -10 in the northern part to +8 - +10 in the southern part, in summer - from +24 - +25 in the northern part to +26 - +27 in the southern part. The maximum temperature recorded on the east coast is 44 degrees.
Animal world
The fauna of the Caspian is represented by 1809 species, of which 415 are vertebrates. IN Caspian Sea 101 species of fish have been registered, and most of the world's sturgeon stocks are concentrated in it, as well as such freshwater fish as roach, carp, pike perch. Caspian Sea- habitat for fish such as carp, mullet, sprat, kutum, bream, salmon, perch, pike. IN Caspian Sea also inhabited by a marine mammal - the Caspian seal.
Vegetable world
Vegetable world Caspian Sea and its coast is represented by 728 species. From plants to Caspian Sea algae predominate - blue-green, diatoms, red, brown, char and others, from flowering ones - zoster and ruppia. By origin, the flora belongs mainly to the Neogene age, however, some plants were brought into Caspian Sea by a person consciously or on the bottoms of ships.
Mining of oil and gas
IN Caspian Sea many oil and gas fields are being developed. Proven oil resources in Caspian Sea are about 10 billion tons, the total resources of oil and gas condensate are estimated at 18 - 20 billion tons.
Oil production in Caspian Sea began in 1820, when the first oil well was drilled on the Absheron shelf. In the second half of the 19th century, oil production began on an industrial scale on the Absheron Peninsula, and then on other territories.
In addition to oil and gas production, on the coast Caspian Sea and the Caspian shelf, salt, limestone, stone, sand, and clay are also being mined.
Ecological problems
Ecological problems Caspian Sea associated with water pollution as a result of oil production and transportation on the continental shelf, the flow of pollutants from the Volga and other rivers flowing into Caspian Sea, the vital activity of coastal cities, as well as the flooding of individual facilities due to an increase in the level Caspian Sea. Predatory harvesting of sturgeons and their caviar, rampant poaching lead to a decrease in the number of sturgeons and forced restrictions on their production and export.
In a dry and hot climate, a large amount of sea water evaporates, water molecules pass into the air. So, every year such a huge amount of water particles is carried away from the surface of the Caspian Sea that all together they would fill a bowl with a volume of several hundred cubic kilometers. This amount of water could fill ten such reservoirs, which will be Kuibyshev.
But can water from the sea surface get into the bottom layers of the Caspian, to a depth of 900-980 meters?
This is possible provided that the density of the surface layers of water is greater than the density of the bottom layers.
It is known that the density of sea water depends on salinity and temperature. The more salts the water contains, the denser it is, and therefore heavier. High temperature water is less dense than cold water. Only at low temperatures (about 0-4°C) is the reverse ratio given, when the water becomes denser as it heats up.
The high salinity of the surface layers of the sea is created in the hot season, when water evaporates strongly, while salt remains in the sea. At this time, the salinity of surface waters is not less, and even somewhat greater than the salinity of the deep and bottom layers.
The temperature of surface waters in the warm season is the same everywhere, about 25-28 °, that is, five times higher than at a depth of 150-200 meters. With the onset of the cold season, the temperature of the surface layers decreases and in a certain period it turns out to be 5-6° above zero.
The temperature of the near-bottom and deep (deeper than 150-200 m) layers of the Caspian Sea is the same (5-6 °), practically unchanged throughout the year.
Under these conditions, the lowering of denser surface cold and highly saline water into the bottom layers is possible.
Only in the southern regions of the Caspian, the temperature of surface water, as a rule, does not drop to 5-6°C even in winter. And, although the sinking of surface waters into the depths cannot occur directly in these areas, water is brought here by deep currents, which has descended from the surface in the more northern parts of the sea.
A similar phenomenon is observed in the eastern part of the border zone between the Middle and South Caspian, where cooled surface waters descend along the southern slope of the border underwater threshold and then follow the deep current to the southern regions of the sea.
Such widespread mixing of surface and deep waters is confirmed by the fact that oxygen has been found at all depths of the Caspian Sea.
Oxygen can get to the depths only with the surface layers of water, where it comes directly from the atmosphere or as a result of photosynthesis.
If there was no continuous supply of oxygen to the bottom layers, it would quickly be absorbed by animal organisms there or spent on the oxidation of the organic matter of the soil. Instead of oxygen, the bottom layers would be saturated with hydrogen sulfide, which is observed in the Black Sea. In it, the vertical circulation is so weak that oxygen in sufficient quantities does not reach the depth, where hydrogen sulfide is formed.
Although oxygen is found at all depths of the Caspian Sea, it is far from being in the same amount in different seasons of the year.
The water column is richest in oxygen in winter. The more severe the winter, that is, the lower the temperature on the surface, the more intense the aeration process, which reaches the deepest parts of the sea. Conversely, several warm winters in a row can cause the appearance of hydrogen sulfide in the bottom layers and even the complete disappearance of oxygen. But such phenomena are temporary and disappear in the first more or less severe winter.
The upper water column is especially rich in dissolved oxygen up to a depth of 100-150 meters. Here, the oxygen content ranges from 5 to 10 cubic meters. cm in litre. At depths of 150-450 m, oxygen is much less - from 5 to 2 cubic meters. cm in litre.
Deeper than 450 m there is very little oxygen and life is very poorly represented - several species of worms and mollusks, the smallest crustaceans.
Mixing of water masses is also caused by surge phenomena and waves.
Waves, currents, winter vertical circulation, surges, surges act constantly and are important factors in the mixing of waters. It is not surprising, therefore, that no matter where in the Caspian Sea we take a sample of water, everywhere its chemical composition will be constant. If there was no mixing of waters, all living organisms of great depths would die out. Life would be possible only in the zone of photosynthesis.
Where the waters mix well and this process proceeds quickly, for example, in shallow areas of the seas and oceans, life is richer.
The constancy of the salt composition of the water of the Caspian Sea is a common property of the waters of the World Ocean. But this does not mean that the chemical composition of the Caspian is the same as in the ocean or in any sea connected to the ocean. Consider a table showing the salt content in the waters of the ocean, the Caspian and the Volga.
|
Carbonates (CaCO 3) |
Sulphates CaSO 4 , MgSO 4 |
Chlorides NaCl, KCl, MgCl 2 |
Average salinity of waters ‰ |
|
|
Ocean |
0,21 |
10,34 |
89,45 |
|
|
Caspian Sea |
1,24 |
30,54 |
67,90 |
12,9 |
|
Volga river |
57,2 |
33,4 |
The table shows that ocean water has very little in common with river water in terms of salt composition. In terms of salt composition, the Caspian Sea occupies an intermediate position between a river and an ocean, which is explained by the great influence of river runoff on the chemical composition of Caspian water. The ratio of salts dissolved in water Aral Sea, closer to the salt composition of river water. This is understandable, since the ratio of the volume of river runoff to the volume of the waters of the Aral Sea is much larger than for the Caspian. A large number of sulfate salts in the Caspian Sea gives its water a bitter-salty taste that distinguishes it from the waters of the oceans and the seas connected to them
The salinity of the Caspian Sea is continuously increasing towards the south. In the pre-estuary space of the Volga, a kilogram of water contains hundredths of a gram of salts. In the eastern regions of the South and Middle Caspian, salinity reaches 13-14‰
The concentration of salts in the Caspian water is low. So, almost twenty times more salts can be dissolved in this water than there are in it.
B.A. Shlyamin. Caspian Sea. 1954
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The Caspian Sea is inland and is located in a vast continental depression on the border of Europe and Asia. The Caspian Sea has no connection with the ocean, which formally allows it to be called a lake, but it has all the features of the sea, since it had connections with the ocean in past geological epochs.
The area of the sea is 386.4 thousand km2, the volume of water is 78 thousand m3.
The Caspian Sea has a vast drainage basin, with an area of about 3.5 million km2. The nature of landscapes, climatic conditions and types of rivers are different. Despite its vastness, only 62.6% of its area is in waste areas; about 26.1% - for drainless. The area of the Caspian Sea itself is 11.3%. 130 rivers flow into it, but almost all of them are located in the north and west (and the eastern coast does not have a single river reaching the sea at all). The largest river in the Caspian basin is the Volga, which provides 78% of the river water entering the sea (it should be noted that more than 25% of the Russian economy is located in the basin of this river, and this undoubtedly determines many other features of the waters of the Caspian Sea), as well as the Kura River , Zhaiyk (Ural), Terek, Sulak, Samur.
Physically and geographically, the sea is divided into three parts: northern, middle and southern. The conditional boundary between the northern and middle parts runs along the line of Chechen Island–Cape Tyub-Karagan, between the middle and southern parts - along the line of Zhiloy Island–Cape Kuuli.
The shelf of the Caspian Sea, on average, is limited to depths of about 100 m. The continental slope, which begins below the edge of the shelf, ends in the middle part at about 500–600 m, in the southern part, where it is very steep, at 700–750 m.
The northern part of the sea is shallow, its average depth is 5–6 m, the maximum depths of 15–20 m are located on the border with the middle part of the sea. The bottom relief is complicated by the presence of banks, islands, furrows.
The middle part of the sea is a separate basin, the region of maximum depths of which - Derbent - is shifted to the western coast. The average depth of this part of the sea is 190 m, the greatest is 788 m.
The southern part of the sea is separated from the middle part by the Apsheron threshold, which is a continuation of . Depths above this underwater ridge do not exceed 180 m. The deepest part of the South Caspian basin with a maximum sea depth of 1025 m is located east of the Kura delta. Several underwater ridges up to 500 m high rise above the bottom of the basin.
The shores of the Caspian Sea are diverse. In the northern part of the sea, they are quite strongly indented. Here are the bays of Kizlyar, Agrakhan, Mangyshlak and many shallow bays. Notable peninsulas: Agrakhansky, Buzachi, Tyub-Karagan, Mangyshlak. Large islands in the northern part of the sea are Tyuleniy, Kulaly. In the deltas of the Volga and Ural rivers, the coastline is complicated by many islets and channels, which often change their position. Many small islands and banks are located on other parts of the coastline.
The middle part of the sea has a relatively flat coastline. On the western coast, on the border with the southern part of the sea, the Apsheron Peninsula is located. To the east of it, islands and banks of the Apsheron archipelago stand out, of which the largest is Zhiloy Island. The eastern shore of the Middle Caspian is more indented, the Kazakh Bay stands out here with the Kenderli Bay and several capes. The largest bay of this coast is.
South of the Absheron Peninsula are the islands of the Baku archipelago. The origin of these islands, as well as some banks off the eastern coast of the southern part of the sea, is associated with the activity of underwater mud volcanoes lying at the bottom of the sea. On the eastern shore are the large bays of Turkmenbashi and Turkmensky, and near it is the island of Ogurchinsky.
One of the most striking phenomena of the Caspian Sea is the periodic variability of its level. In historical times, the Caspian Sea had a lower level than the World Ocean. Fluctuations in the level of the Caspian Sea are so great that for more than a century they have attracted the attention of not only scientists. Its peculiarity is that in the memory of mankind its level has always been below the level of the World Ocean. Since the beginning of instrumental observations (since 1830) of the sea level, the amplitude of its fluctuations has been almost 4 m, from -25.3 m in the eighties of the XIX century. to -29 m in 1977. In the last century, the level of the Caspian Sea has changed significantly twice. In 1929 it stood at a mark of about -26 m, and since it had been close to this mark for almost a century, this position of the level was considered as a long-term or secular average. In 1930, the level began to decline rapidly. Already by 1941, it had dropped by almost 2 m. This led to the drying up of vast coastal areas of the bottom. The decrease in the level, with its small fluctuations (short-term insignificant rises in the level in 1946-1948 and 1956-1958), continued until 1977 and reached the mark of -29.02 m, i.e., the level took the lowest position for last 200 years.
In 1978, contrary to all forecasts, the sea level began to rise. As of 1994, the level of the Caspian Sea was at -26.5 m, that is, in 16 years the level has risen by more than 2 m. The rate of this rise is 15 cm per year. The level increment in some years was higher, and in 1991 it reached 39 cm.
The general fluctuations in the level of the Caspian Sea are superimposed by its seasonal changes, the average long-term of which reaches 40 cm, as well as surge phenomena. The latter are especially pronounced in the Northern Caspian. The northwestern coast is characterized by large surges created by the prevailing, especially in the cold season, storms of eastern and southeastern directions. Over the past decades, a number of large (more than 1.5–3 m) surges have been observed here. A particularly large surge with catastrophic consequences was noted in 1952. Fluctuations in the level of the Caspian Sea cause great damage to the states surrounding its water area.
Climate. The Caspian Sea is located in temperate and subtropical. Climatic conditions change in the meridional direction, since the sea stretches for almost 1200 km from north to south.
In the Caspian region, various circulation systems interact, however, easterly winds prevail throughout the year (the influence of the Asian high). The position in rather low latitudes provides a positive balance of heat inflow, so the Caspian Sea serves as a source of heat and moisture for most of the year for those passing by. The average annual temperature in the northern part of the sea is 8–10°С, in the middle part - 11–14°С, in the southern part – 15–17°С. However, in the northernmost parts of the sea, the average January temperature is from –7 to –10°С, and the minimum during intrusions is up to –30°С, which determines the formation of the ice cover. In summer, rather high temperatures dominate over the entire region under consideration - 24–26°С. Thus, the Northern Caspian is subject to the most sharp temperature fluctuations.
The Caspian Sea is characterized by a very small amount of precipitation per year - only 180 mm, and most of it falls on the cold season of the year (from October to March). However, the Northern Caspian differs in this respect from the rest of the basin: here the average annual precipitation is less (only 137 mm for the western part), and the distribution over the seasons is more even (10–18 mm per month). In general, we can talk about proximity to arid ones.
Water temperature. Distinctive features of the Caspian Sea (large differences in depths in different parts of the sea, nature, isolation) have a certain influence on the formation of temperature conditions. In the shallow North Caspian, the entire water column can be considered as homogeneous (the same applies to shallow bays located in other parts of the sea). In the Middle and South Caspian, surface and deep masses separated by a transitional layer can be distinguished. In the Northern Caspian and in the surface layers of the Middle and Southern Caspian, the water temperature varies over a wide range. In winter, temperatures vary from north to south from less than 2 to 10°С, the water temperature near the western coast is 1–2°С higher than near the eastern one, in the open sea the temperature is higher than near the coasts: by 2–3°С in the middle part and by 3–4°С in the southern part of the sea. In winter, the temperature distribution is more uniform with depth, which is facilitated by the winter vertical circulation. During moderate and severe winters in the northern part of the sea and shallow bays on the east coast, the water temperature drops to freezing.
In summer, the temperature varies in space from 20 to 28°C. The highest temperatures are observed in the southern part of the sea; temperatures are also quite high in the well-warmed shallow North Caspian. The zone of distribution of the lowest temperatures is adjacent to the east coast. This is due to the rise of cold deep waters to the surface. Temperatures are also relatively low in the poorly heated deep-water central part. In the open areas of the sea, in late May–early June, the formation of a temperature jump layer begins, which is most clearly expressed in August. Most often it is located between 20 and 30 m in the middle part of the sea and 30 and 40 m in the south. In the middle part of the sea, due to the surge near the eastern coast, the shock layer rises close to the surface. In the bottom layers of the sea, the temperature during the year is about 4.5°C in the middle part and 5.8–5.9°C in the south.
Salinity. Salinity values are determined by such factors as river runoff, water dynamics, including mainly wind and gradient currents, the resulting water exchange between the western and eastern parts of the Northern Caspian and between the Northern and Middle Caspian, the bottom topography, which determines the location of waters with different , mainly along isobath, evaporation, providing a shortage of fresh water and an influx of more saline. These factors collectively affect the seasonal differences in salinity.
The Northern Caspian can be considered as a constant mixture of river and Caspian waters. The most active mixing occurs in the western part, where both river and Central Caspian waters directly enter. In this case, horizontal salinity gradients can reach 1‰ per 1 km.
The eastern part of the Northern Caspian is characterized by a more uniform salinity field, since most of the river and sea (Middle Caspian) waters enter this area of the sea in a transformed form.
According to the values of horizontal salinity gradients, in the western part of the Northern Caspian, a river-sea contact zone can be distinguished with water salinity from 2 to 10‰, in the eastern part from 2 to 6‰.
Significant vertical salinity gradients in the Northern Caspian are formed as a result of the interaction of river and sea waters, with runoff playing a decisive role. The intensification of vertical stratification is also facilitated by the unequal thermal state of the water layers, since the temperature of the surface desalinated waters coming from the coast in summer is 10–15°C higher than that of the bottom ones.
In the deep basins of the Middle and South Caspian, salinity fluctuations in the upper layer are 1–1.5‰. The largest difference between the maximum and minimum salinity was noted in the area of the Apsheron threshold, where it is 1.6‰ in the surface layer and 2.1‰ at the 5 m horizon.
The decrease in salinity along the western coast of the South Caspian in the 0–20 m layer is caused by the runoff of the Kura River. The influence of the Kura runoff decreases with depth; at the horizons of 40–70 m, the range of salinity fluctuations is no more than 1.1‰. Along the entire western coast to the Absheron Peninsula stretches a strip of desalinated water with a salinity of 10–12.5‰ coming from the Northern Caspian.
In addition, salinity increases in the South Caspian due to the removal of saline waters from bays and inlets on the eastern shelf under the action of southeasterly winds. In the future, these waters are transferred to the Middle Caspian.
In the deep layers of the Middle and South Caspian, salinity is about 13‰. In the central part of the Middle Caspian, such salinity is observed at horizons below 100 m, and in the deep part of the South Caspian, the upper boundary of waters with increased salinity drops to 250 m. Obviously, vertical mixing of waters is difficult in these parts of the sea.
Surface water circulation. Currents in the sea are mainly wind-driven. In the western part of the Northern Caspian, currents of the western and eastern quarters are most often observed, in the eastern - southwestern and southern. The currents caused by the runoff of the Volga and Ural rivers can be traced only within the estuarine coast. The prevailing current velocities are 10–15 cm/s; in the open areas of the Northern Caspian, the maximum velocities are about 30 cm/s.
In the coastal areas of the middle and southern parts of the sea, currents of the northwestern, northern, southeastern, and southern directions are observed in accordance with the wind directions; eastward currents often occur near the eastern coast. Along the western coast of the middle part of the sea, the most stable currents are southeast and south. Current velocities are on average about 20–40 cm/s, the maximum ones reach 50–80 cm/s. Other types of currents also play a significant role in the circulation of sea waters: gradient, seiche, inertial ones.
ice formation. The Northern Caspian is covered with ice annually in November, the area of the freezing part of the water area depends on the severity of the winter: in severe winters, the entire Northern Caspian is covered with ice, in soft ice it stays within the 2–3 meter isobath. The appearance of ice in the middle and southern parts of the sea falls on December-January. Near the eastern coast, ice is of local origin, near the western coast - most often brought from the northern part of the sea. In severe winters, shallow bays freeze off the eastern coast of the middle part of the sea, coasts and landfast ice form off the coast, and drift ice spreads to the Absheron Peninsula in abnormally cold winters off the western coast. The disappearance of the ice cover is observed in the second half of February–March.
Oxygen content. The spatial distribution of dissolved oxygen in the Caspian Sea has a number of regularities.
The central part of the Northern Caspian is characterized by a fairly uniform distribution of oxygen. An increased oxygen content is found in the areas of the pre-estuary seashore of the Volga River, a lower one - in the southwestern part of the Northern Caspian.
In the Middle and South Caspian, the highest oxygen concentrations are confined to coastal shallow areas and pre-estuary seashores of rivers, with the exception of the most polluted areas of the sea (Baku Bay, Sumgait region, etc.).
In the deep-water regions of the Caspian Sea, the main pattern is preserved in all seasons - a decrease in oxygen concentration with depth.
Due to the autumn-winter cooling, the density of the waters of the North Caspian increases to a value at which it becomes possible for the flow of North Caspian waters with a high oxygen content along the continental slope to significant depths of the Caspian Sea.
The seasonal distribution of oxygen is mainly related to the annual course and seasonal ratio of production-destruction processes occurring in the sea.
In spring, the production of oxygen in the process of photosynthesis quite significantly covers the decrease in oxygen due to a decrease in its solubility with an increase in water temperature in spring.
In the areas of the estuarine coasts of the rivers feeding the Caspian Sea, in spring there is a sharp increase in the relative oxygen content, which in turn is an integral indicator of the intensification of the photosynthesis process and characterizes the degree of productivity of the mixing zones of sea and river waters.
In summer, due to significant heating and activation of photosynthesis processes, the leading factors in the formation of the oxygen regime in surface waters are photosynthetic processes, in near-bottom waters - biochemical oxygen consumption by bottom sediments.
Due to the high temperature of the waters, the stratification of the water column, the large influx of organic matter and its intense oxidation, oxygen is quickly consumed with its minimal entry into the lower layers of the sea, as a result of which an oxygen deficiency zone is formed in the Northern Caspian. Intensive photosynthesis in the open waters of the deep-water regions of the Middle and South Caspian covers the upper 25-meter layer, where oxygen saturation is more than 120%.
In autumn, in the well-aerated shallow water areas of the Northern, Middle and Southern Caspian, the formation of oxygen fields is determined by the processes of water cooling and the less active, but still ongoing process of photosynthesis. The oxygen content is rising.
The spatial distribution of nutrients in the Caspian Sea reveals the following patterns:
- increased concentrations of biogenic substances characterize the areas of pre-estuary seashores of rivers that feed the sea and shallow areas of the sea subject to active anthropogenic influence (Baku Bay, Turkmenbashi Bay, water areas adjacent to Makhachkala, Fort Shevchenko, etc.);
- The Northern Caspian, which is a vast mixing zone of river and sea waters, is characterized by significant spatial gradients in the distribution of nutrients;
- in the Middle Caspian, the nature of circulation contributes to the upwelling of deep waters with a high content of nutrients into the overlying layers of the sea;
- in the deep water areas of the Middle and South Caspian, the vertical distribution of nutrients depends on the intensity of the convective mixing process, and their content increases with depth.
The dynamics of nutrient concentrations during the year in the Caspian Sea is influenced by such factors as seasonal fluctuations in the biogenic runoff into the sea, the seasonal ratio of production-destruction processes, the intensity of exchange between soil and water mass, ice conditions in winter in the Northern Caspian, the processes of winter vertical circulation in the deep sea areas.
In winter, a significant area of the Northern Caspian is covered with ice, but biochemical processes are actively developing in the under-ice water and ice. The ice of the Northern Caspian, being a kind of accumulator of biogenic substances, transforms these substances entering the sea from and from the atmosphere.
As a result of the winter vertical circulation of waters in the deep-sea regions of the Middle and Southern Caspian in the cold season, the active layer of the sea is enriched with nutrients due to their supply from the underlying layers.
Spring for the waters of the North Caspian is characterized by a minimum content of phosphates, nitrites and silicon, which is explained by the spring outbreak of phytoplankton development (silicon is actively consumed by diatoms). High concentrations of ammonium and nitrate nitrogen, characteristic of the waters of a large area of the Northern Caspian during floods, are due to intensive flushing by river waters.
In the spring season, in the area of water exchange between the Northern and Middle Caspian in the subsurface layer, with the maximum oxygen content, the content of phosphates is minimal, which, in turn, indicates the activation of the photosynthesis process in this layer.
In the South Caspian, the distribution of nutrients in spring is basically similar to their distribution in the Middle Caspian.
In the summer, in the waters of the Northern Caspian, a redistribution of various forms of biogenic compounds is found. Here, the content of ammonium nitrogen and nitrates significantly decreases, while at the same time there is a slight increase in the concentrations of phosphates and nitrites and a rather significant increase in the concentration of silicon. In the Middle and South Caspian, the concentration of phosphates has decreased due to their consumption in the process of photosynthesis and the difficulty of water exchange with the deep water accumulation zone.
In autumn, in the Caspian Sea, due to the cessation of the activity of some types of phytoplankton, the content of phosphates and nitrates increases, and the concentration of silicon decreases, as an autumn outbreak of diatoms occurs.
Oil has been produced on the shelf of the Caspian Sea for more than 150 years.
Currently, large reserves of hydrocarbons are being developed on the Russian shelf, the resources of which on the Dagestan shelf are estimated at 425 million tons of oil equivalent (of which 132 million tons of oil and 78 billion m3 of gas), on the shelf of the Northern Caspian - 1 billion tons of oil .
In total, about 2 billion tons of oil have already been produced in the Caspian.
Losses of oil and products of its processing during extraction, transportation and use reach 2% of the total volume.
The main sources of pollutants, including oil products, entering the Caspian Sea are carry-over with river runoff, discharge of untreated industrial and agricultural effluents, domestic wastewater from cities and towns located on the coast, shipping, exploration and exploitation of oil and gas fields located at the bottom of the sea, transportation of oil by sea. 90% of the places where pollutants enter with river runoff are concentrated in the Northern Caspian, industrial ones are confined mainly to the area of the Apsheron Peninsula, and increased oil pollution of the Southern Caspian is associated with oil production and oil exploration drilling, as well as with active volcanic activity (mud) in the zone oil and gas structures.
From the territory of Russia, about 55 thousand tons of oil products enter the Northern Caspian every year, including 35 thousand tons (65%) from the Volga River and 130 tons (2.5%) from the Terek and Sulak rivers.
The thickening of the film on the water surface up to 0.01 mm disrupts the processes of gas exchange and threatens the death of hydrobiota. Toxic for fish is the concentration of oil products 0.01 mg/l, for phytoplankton - 0.1 mg/l.
The development of oil and gas resources of the bottom of the Caspian Sea, the estimated reserves of which are estimated at 12–15 billion tons of standard fuel, will become the main factor in the anthropogenic load on the ecosystem of the sea in the coming decades.
Caspian autochthonous fauna. The total number of autochthons is 513 species or 43.8% of the entire fauna, which include herring, gobies, mollusks, etc.
arctic views. The total number of the Arctic group is 14 species and subspecies, or only 1.2% of the entire fauna of the Caspian (mysids, sea cockroach, white salmon, Caspian salmon, Caspian seal, etc.). The basis of the Arctic fauna is crustaceans (71.4%), which easily tolerate desalination and live at great depths of the Middle and South Caspian (from 200 to 700 m), since the lowest water temperatures (4.9– 5.9°C).
mediterranean views. These are 2 types of mollusks, needle-fish, etc. At the beginning of the 20s of our century, the mollusk mitilyastra penetrated here, later 2 types of shrimp (with mullets, during their acclimatization), 2 types of mullet and flounder. Some species entered the Caspian after the opening of the Volga-Don Canal. Mediterranean species play a significant role in the fish food base of the Caspian Sea.
Freshwater fauna (228 species). This group includes anadromous and semi-anadromous fish (sturgeon, salmon, pike, catfish, cyprinids, as well as rotifers).
sea views. These are ciliates (386 forms), 2 species of foraminifera. There are especially many endemics among higher crustaceans (31 species), gastropod mollusks (74 species and subspecies), bivalve mollusks (28 species and subspecies) and fish (63 species and subspecies). The abundance of endemics in the Caspian Sea makes it one of the most unique brackish water bodies on the planet.
The Caspian Sea provides more than 80% of the world's sturgeon catch, most of which falls on the North Caspian.
To increase the catches of sturgeon, which dropped sharply during the years of sea level drop, a set of measures is being implemented. Among them - a complete ban on sturgeon fishing in the sea and its regulation in rivers, an increase in factory breeding of sturgeons.
The Caspian Sea is the largest drainless lake on Earth, located at the junction of Europe and Asia, called the sea due to the fact that its bed is composed of oceanic-type earth's crust. The Caspian Sea is a drainless lake, and the water in it is salty, from 0.05 ‰ near the mouth of the Volga to 11-13 ‰ in the southeast. The water level is subject to fluctuations, according to 2009 data it was 27.16 m below sea level. The Caspian Sea is located at the junction of two parts of the Eurasian continent - Europe and Asia. The length of the Caspian Sea from north to south is about 1200 kilometers, from west to east - from 195 to 435 kilometers, an average of 310-320 kilometers. The Caspian Sea is conditionally divided according to physical and geographical conditions into 3 parts - the Northern Caspian, the Middle Caspian and the Southern Caspian. The conditional border between the North and Middle Caspian runs along the line of about. Chechnya - Cape Tyub-Karagansky, between the Middle and South Caspian - along the line of about. Residential - Cape Gan-Gulu. The area of the Northern, Middle and Southern Caspian is 25, 36, 39 percent respectively.
The length of the coastline of the Caspian Sea is estimated at about 6500-6700 kilometers, with islands - up to 7000 kilometers. The shores of the Caspian Sea in most of its territory are low-lying and smooth. In the northern part, the coastline is indented by water channels and islands of the Volga and Ural deltas, the shores are low and swampy, and the water surface is covered with thickets in many places. The east coast is dominated by limestone shores adjacent to semi-deserts and deserts. The most winding coasts are on the west coast in the area of the Apsheron Peninsula and on the east coast in the area of the Kazakh Gulf and Kara-Bogaz-Gol. The territory adjacent to the Caspian Sea is called the Caspian Sea.
The Caspian Sea is the largest enclosed body of water on the planet Earth, located on the continent of Eurasia - in the border area of the states of Russia, Kazakhstan, Turkmenistan, Iran and Azerbaijan. In fact, it is a giant lake left after the disappearance of the ancient Tethys ocean. Nevertheless, there is every reason to consider it as an independent sea (this is indicated by salinity, a large area and decent depth, the bottom of the oceanic crust and other signs). In terms of maximum depth, it is the third among closed reservoirs - after lakes Baikal and Tanganyika. In the northern part of the Caspian Sea (a few kilometers from the northern coast - parallel to it) there is a geographical border between Europe and Asia.
Toponymy
- Other names: throughout the history of mankind, different peoples of the Caspian Sea had about 70 different names. The most famous of them are: Khvalynskoe or Khvalisskoe (it took place in the times of Ancient Rus', arose by the name of the people praise, who lived in the Northern Caspian and traded with the Russians), Girkan or Dzhurdzhan (derived from the alternative names of the city of Gorgan, located in Iran), Khazar, Abeskun (after the name of the island and city in the Kura delta - now flooded), Saray, Derbent, Sikhay .
- Origin of name: according to one of the hypotheses, the Caspian Sea received its modern and most ancient name from a tribe of nomadic horse breeders the Caspians who lived in the 1st millennium BC on the southwestern coast.
Morphometry
- Catchment area: 3,626,000 km².
- Mirror area: 371,000 km².
- Coastline length: 7,000 km.
- Volume: 78,200 km³.
- Average depth: 208 m
- Max Depth: 1025 m.
Hydrology
- The presence of a constant flow: no, it's pointless.
- Tributaries:, Ural, Emba, Atrek, Gorgan, Heraz, Sefidrud, Astarchay, Kura, Pirsagat, Kusarchay, Samur, Rubas, Darvagchay, Ulluchay, Shuraozen, Sulak, Terek, Kuma.
- Bottom: very varied. At shallow depths, sandy soil with an admixture of shells is common, in deep water places - silty. Pebble and rocky places can be found in the coastal strip (especially where mountain ranges adjoin the sea). In the estuarine areas, the underwater soil consists of river sediments. The Kara-Bogaz-Gol bay is notable for the fact that its bottom is a powerful layer of mineral salts.
Chemical composition
- Water: brackish.
- Salinity: 13 g / l.
- Transparency: 15 m.
Geography
Rice. 1. Map of the Caspian Sea basin.
- Coordinates: 41°59′02″ s. sh., 51°03′52″ E d.
- Height above sea level:-28 m.
- Coastal landscape: Due to the fact that the coastline of the Caspian Sea is very long, and it is located in different geographical zones, the coastal landscape is diverse. In the northern part of the reservoir, the shores are low, swampy, in places of the deltas of large rivers they are indented by numerous channels. The eastern shores are mostly limestone - desert or semi-desert. The western and southern shores adjoin mountain ranges. The greatest indentation of the coastline is observed in the west - in the area of the Apsheron Peninsula, as well as in the east - in the area of the Kazakh and Kara-Bogaz-Gol bays.
- Settlements on the coast:
- Russia: Astrakhan, Derbent, Kaspiysk, Makhachkala, Olya.
- Kazakhstan: Aktau, Atyrau, Kuryk, Sogandyk, Bautino.
- Turkmenistan: Ekerem, Karabogaz, Turkmenbashi, Khazar.
- Iran: Astara, Balboser, Bender-Torkemen, Bender-Anzeli, Neka, Chalus.
- Azerbaijan: Alyat, Astara, Baku, Dubendi, Lankaran, Sangachali, Sumgayit.
interactive map
Ecology
The ecological situation in the Caspian Sea is far from ideal. Almost all large rivers flowing into it are polluted by the effluents of industrial enterprises located upstream. This could not but affect the presence of pollutants in the waters and bottom sediments of the Caspian - over the past half century, their concentration has increased markedly, and the content of some heavy metals has already exceeded the permissible limits.
In addition, the waters of the Caspian Sea are constantly polluted by domestic wastewater from coastal cities, as well as during oil production on the continental shelf, and during its transportation.
Fishing in the Caspian Sea
- Fish species:
- Artificial settlement: not all of the above fish species in the Caspian Sea are native. About 4 dozen species came by chance (for example, through channels from the basins of the Black and Baltic Seas), or were deliberately populated by humans. An example is the mullet. Three Black Sea species of these fish - striped mullet, sharp-nosed mullet and golden mullet - were released in the first half of the 20th century. The striped mullet did not take root, but the blackfin with golden mullet have successfully acclimatized, and by the current moment they have settled in virtually the entire water area of the Caspian Sea, having formed several commercial herds. At the same time, fish feed faster than in the Black Sea, and reach larger sizes. In the second half of the last century (starting from 1962), attempts were also made to populate such Far Eastern salmon fish as pink salmon and chum salmon in the Caspian Sea. In total, several billion fry of these fish were released into the sea within 5 years. Pink salmon did not survive in the new range, but on the contrary, chum salmon successfully took root and even began to spawn in the rivers flowing into the sea. However, she could not reproduce in sufficient quantities and gradually disappeared. There are as yet no favorable conditions for its full-fledged natural reproduction (there are very few places where spawning and development of fry could successfully occur). To ensure them, river reclamation is needed, otherwise, without human help (artificial sampling of eggs and its incubation), fish will not be able to maintain their numbers.
Fishing places
In fact, fishing is possible at any point on the coast of the Caspian Sea, which can be reached by land or water. Which species of fish will be caught at the same time depends on local conditions, but to a greater extent on whether rivers flow here. As a rule, in places where estuaries and deltas (especially large watercourses) are located, the water in the sea is strongly desalinated, therefore, freshwater fish (carp, catfish, bream, etc.) usually predominate in catches; rivers (barbels, shemaya). Of the marine species in desalinated areas, those for which salinity does not matter are caught (mullet, some of the gobies). In certain periods of the year, semi-anadromous and migratory species can be found here, feeding in the sea, and entering the rivers for spawning (sturgeon, some of the herring, Caspian salmon). In places where there are no flowing rivers, freshwater species are found in a slightly smaller number, but at the same time, marine fish appear, usually avoiding desalinated areas (for example, sea zander). Away from the coast, fish that prefer salt water and deep-sea species are caught.
Conventionally, 9 places or areas of interest in terms of fishing can be distinguished:
- North Shore (RF)- this area is located on the northern coast of the Russian Federation (from the Volga delta to the Kizlyar Bay). Its main features are the insignificant salinity of the water (the lowest in the Caspian Sea), shallow depth, the presence of multiple shoals, islands, and highly developed aquatic vegetation. In addition to the Volga delta with its numerous channels, bays and erics, it also includes the estuarine seaside, called the Caspian peals. These places are popular with Russian fishermen, and for good reason: the conditions for fish are very favorable here, and there is also a good forage base. The ichthyofauna in these parts may not shine with a richness of species, but it is distinguished by its abundance, and some of its representatives reach a very considerable size. Usually the basis of catches are freshwater fish, typical for the Volga basin. Most often caught: perch, pike perch, roach (more precisely, its varieties, called roach and ram), rudd, asp, sabrefish, bream, goldfish, carp, catfish, pike. Bursh, silver bream, white-eye, blue bream are somewhat less common. There are also representatives of sturgeons (sturgeon, stellate sturgeon, beluga, etc.), salmonids (nelma, brown trout - Caspian salmon) in these places, but their catch is prohibited.
- Northwestern coast (RF)- this section covers the western coast of the Russian Federation (from Kizlyar Bay to Makhachkala). The Kuma, Terek and Sulak rivers flow here - they carry their waters both along natural channels and artificial channels. In this area there are bays, among which are quite large ones (Kizlyarsky, Agrakhansky). The sea in these places is shallow. Of the fish in the catches, freshwater species predominate: pike, perch, carp, catfish, rudd, bream, barbel, etc., marine species are also caught here, for example, herring (black-backed, shad).
- West Bank (RF)- from Makhachkala to the border of the Russian Federation with Azerbaijan. An area where mountain ranges adjoin the sea. The salinity of the water here is somewhat higher than in previous places, therefore, marine species are more common in the catches of fishermen (sea pike, mullet, herring). However, freshwater fish are by no means uncommon.
- West Bank (Azerbaijan)- from the border of the Russian Federation with Azerbaijan to the Absheron Peninsula. Continuation of the section where mountain ranges adjoin the sea. Fishing here is even more similar to typical sea fishing, thanks to fish such as hart and golden mullet (mullet) and several types of gobies, which are also caught here. In addition to them, there are kutum, herring, and some typically freshwater species, for example, carp.
- Southwest coast (Azerbaijan)- from the Absheron Peninsula to the border of Azerbaijan with Iran. Most of this area is occupied by the delta of the Kura River. Here the same species of fish are caught that were listed in the previous paragraph, but freshwater ones are somewhat more common.
- North Shore (Kazakhstan)- this section covers the northern coast of Kazakhstan. The Ural delta and the Akzhaiyk state reserve are located here, therefore fishing directly in the river delta and in some waters adjacent to it is prohibited. Fishing is possible only outside the reserve - upstream from the delta, or in the sea - at some distance from it. Fishing near the Ural delta has much in common with fishing at the confluence of the Volga - almost the same species of fish are found here.
- Northeast coast (Kazakhstan)- from the mouth of the Emba to Cape Tyub-Karagan. In contrast to the northern part of the sea, where the water is greatly diluted by large rivers flowing into it, its salinity is slightly increased here, therefore, those fish species appear that avoid desalinated areas, for example, sea zander, which is caught in the Dead Kultuk Bay. Also, other representatives of marine fauna are often found in the catches.
- Eastern coast (Kazakhstan, Turkmenistan)- from Cape Tyub-Karagan to the border of Turkmenistan and Iran. Differs in the almost complete absence of flowing rivers. The salinity of the water here is at its highest. Of the fish in these places, marine species predominate, the main catches are mullet, pike perch and gobies.
- South Shore (Iran)- covers the southern coast of the Caspian Sea. Throughout this section, the Elburs mountain range adjoins the sea. Many rivers flow here, most of which are small streams, there are also several medium and one large river. Of the fish, in addition to marine species, there are also some freshwater, as well as semi-anadromous and anadromous species, for example, sturgeons.
Features of fishing
The most popular and catchy amateur tackle that is used on the Caspian coast is a heavy spinning rod converted into a “sea bottom”. Usually it is equipped with a strong spool, on which a fairly thick line (0.3 mm or more) is wound. The thickness of the fishing line is determined not so much by the size of the fish as by the mass of a rather heavy sinker, which is necessary for an ultra-long cast (in the Caspian it is widely believed that the farther from the shore the casting point is, the better). After the sinker comes a thinner fishing line - with several leashes. As a bait, shrimps and amphipods that live in coastal thickets of algae are used - if it is supposed to catch sea fish, or an ordinary bait like a worm, cockchafer larvae and others - if freshwater species are found in the fishing area.
In estuaries of inflowing rivers, other tackle such as float rod, feeder and traditional spinning can be used.
kasparova2 majorov2006 g2gg2g-61 .
Photo 8. Sunset in Aktau.