Water mass. The concept of water masses and biogeographic zoning

The total mass of all the waters of the World Ocean is divided by experts into two types - surface and deep. However, this division is very conditional. A more detailed categorization includes the following several groups, identified on the basis of territorial location.

Definition

First, let's define what water masses are. This designation in geography refers to a sufficiently large volume of water that is formed in one or another part of the ocean. Water masses differ from each other in a number of characteristics: salinity, temperature, as well as density and transparency. Differences are also expressed in the amount of oxygen, the presence of living organisms. We have defined what water masses are. Now we need to consider their different types.

water near the surface

Surface waters are those zones where their thermal and dynamic interaction with air is most active. In accordance with the climatic features inherent in certain zones, they are divided into separate categories: equatorial, tropical, subtropical, polar, subpolar. Schoolchildren who collect information to answer the question of what water masses are need to know about the depth of their occurrence. Otherwise, the answer in the geography lesson will be incomplete.

They reach a depth of 200-250 m. Their temperature often changes, as they are formed by the action of atmospheric precipitation. In the thicknesses of surface waters, waves are formed, as well as horizontal waves. It is here that the largest number of fish and plankton are found. Between the surface and deep masses there is a layer of intermediate water masses. The depth of their location is from 500 to 1000 m. They are formed in areas of high salinity and high levels of evaporation.

Deep water masses

The lower boundary of deep waters can sometimes reach 5000 m. This type of water masses most often occurs in tropical latitudes. They are formed under the influence of surface and intermediate waters. For those interested in what they are and what are the features of their various types, it is also important to have an idea about the speed of the current in the ocean. Deep water masses move very slowly in the vertical direction, but their horizontal speed can be up to 28 km per hour. The next layer is bottom water masses. They are found at depths over 5000 m. This type is characterized by a constant level of salinity, as well as a high level of density.

Equatorial water masses

"What are water masses and their types" - this is one of the obligatory topics of the course secondary school. The student needs to know that waters can be assigned to one or another group, not only depending on their depth, but also on the territorial location. The first type mentioned in accordance with this classification is the equatorial water masses. They are characterized by high temperature (reaches 28°C), low density, low oxygen content. The salinity of these waters is low. Above the equatorial waters there is a belt of low atmospheric pressure.

Tropical water masses

They are also quite well warmed up, and their temperature does not change during different seasons more than 4°C. Ocean currents have a great influence on this type of water. Their salinity is higher, since a zone of high atmospheric pressure is established in this climatic zone, and there is very little precipitation.

moderate water masses

The salinity level of these waters is lower than that of others, because they are desalinated by precipitation, rivers, and icebergs. Seasonally, the temperature of this type of water masses can vary up to 10°C. However, the change of seasons occurs much later than on the mainland. Temperate waters differ depending on whether they are in the western or eastern regions of the ocean. The former, as a rule, are cold, and the latter are warmer due to warming by internal currents.

Polar water masses

What body of water is the coldest? Obviously, they are those that are in the Arctic and off the coast of Antarctica. With the help of currents, they can be carried to temperate and tropical regions. The main features of the polar water masses are floating blocks of ice and huge ice expanses. Their salinity is extremely low. In the Southern Hemisphere sea ​​ice move to the region of temperate latitudes much more often than it happens in the north.

Formation methods

Schoolchildren who are interested in what water masses are will also be interested in learning about their education. The main method of their formation is convection, or mixing. As a result of mixing, the water sinks to a considerable depth, where it again reaches vertical stability. Such a process can occur in several stages, and the depth of convective mixing can reach up to 3-4 km. The next way is subduction, or "diving". With this method of mass formation, water sinks due to the combined action of wind and surface cooling.

Large volumes of water are called water masses, and their natural spatial combination is called the hydrological structure of a reservoir. The main indicators of the water masses of reservoirs, which make it possible to distinguish one water mass from another, are such characteristics as density, temperature, electrical conductivity, turbidity, water transparency and other physical indicators; mineralization of water, the content of individual ions, the content of gases in water and other chemical indicators; the content of phyto- and zooplankton and other biological indicators. The main property of any water mass in a reservoir is its genetic homogeneity.

According to the genesis, two types of water masses are distinguished: primary and main.

Per primary water masses lakes are formed on their watersheds and enter water bodies in the form of river runoff. The properties of these water masses depend on natural features watersheds and change seasonally depending on the phases of the hydrological regime of the rivers. The main feature of the primary water masses of the flood phase is low mineralization, increased water turbidity, and a rather high content of dissolved oxygen. The temperature of the primary water mass during the heating period is usually higher, and during the cooling period - lower than in the reservoir.

Main water masses are formed in the reservoirs themselves; their characteristics reflect the features of the hydrological, hydrochemical and hydrobiological regimes of water bodies. Some of the properties of the main water masses are inherited from the primary water masses, some are acquired as a result of intra-aquatic processes, as well as under the influence of the exchange of matter and energy between the reservoir, the atmosphere and bottom soils. Although the main water masses change their properties during the year, they generally remain more inert than the primary water masses. (Surface water mass is the upper most heated layer of water (epilimnion); deep water mass is usually the most powerful and relatively homogeneous layer of colder water (hypolimnion); intermediate water mass corresponds to the temperature jump layer (metalimnion); bottom water mass is a narrow a layer of water near the bottom, characterized by increased mineralization and specific aquatic organisms.)

The influence of lakes on the natural environment is manifested primarily through river runoff.

There is a general permanent effect of lakes on the water cycle in river basins and a regulatory effect on the intra-annual regime of rivers. - and heat exchange in the hydrographic network. Lakes (as well as reservoirs) are accumulations of water that increase the capacity of the hydrographic network. The lower intensity of water exchange in river systems, including lakes (and reservoirs), has a number of serious consequences: the accumulation of salts in water bodies, organic matter, sediment, heat and other components of river runoff (in the broad sense of the term). Rivers flowing from large lakes, as a rule, carry less salt and sediment (Selenga River - Lake Baikal). In addition, waste lakes (as well as reservoirs) redistribute the river runoff in time, exerting a regulating effect on it and leveling it during the year. Land water bodies have a noticeable effect on local climatic conditions, reducing the continentality of the climate and increasing the duration of spring and autumn, on the intracontinental moisture cycle (slightly), contributing to increased precipitation, the appearance of fog, etc. Water bodies also affect the level of groundwater, generally increasing it , on land cover and animal world adjacent territories, increasing the diversity of species composition, abundance, biomass, etc.



- these are large volumes of water formed in certain parts of the ocean and differ from each other temperature, salinity, density, transparency, the amount of oxygen contained and many other properties. Unlike , in them great importance has vertical zonality.

IN depth dependent There are the following types of water masses:

Surface water masses . They are located deep 200-250 m. Here, the water temperature and salinity often change, as these water masses are formed under the influence of the influx of fresh continental waters. In surface water masses are formed waves And horizontal. In this type of water masses, the highest content of plankton and fish.

Intermediate water masses . They are located deep 500-1000 m. Basically, this type of mass is found in the tropical latitudes of both hemispheres and is formed under conditions of increased evaporation and a constant increase in salinity.

Deep water masses . Their lower limit can reach before 5000 m. Their formation is associated with the mixing of surface and intermediate water masses, polar and tropical masses. Vertically, they move very slowly, but horizontally - at a speed of 28 m / h.

Bottom water masses . They are located in below 5000 m, have a constant salinity and a very high density.

Water masses can be classified not only depending on the depth, but also by origin. In this case, the following types of water masses are distinguished:

Equatorial water masses . They are well warmed by the sun, their temperature changes seasonally by no more than 2° and is 27-28°C. They are desalinated by abundant atmospheric precipitation and flowing into the ocean at these latitudes, so the salinity of these waters is lower than in tropical latitudes.

Tropical water masses . They are also well warmed by the sun, but the water temperature here is lower than in equatorial latitudes, and is 20-25°C. Seasonally, the temperature of the waters of tropical latitudes varies by 4 °. The temperature of the waters of this type of water mass is greatly influenced by ocean currents: the western parts of the oceans, where warm currents come from the equator, are warmer than the eastern parts, since cold currents come there. The salinity of these waters is much higher than that of the equatorial ones, since here, as a result of descending air currents, high pressure is established and little precipitation falls. Rivers also do not have a desalination effect, since there are very few of them in these latitudes.

moderate water masses . Seasonally, the temperature of the waters of these latitudes differs by 10°: in winter, the water temperature ranges from 0° to 10°C, and in summer it varies from 10° to 20°C. For these waters, the change of seasons is already characteristic, but it comes later than on land, and is not so pronounced. The salinity of these waters is lower than that of tropical waters, since atmospheric precipitation, rivers flowing into these waters, and entering these latitudes have a desalination effect. Temperature differences between western and eastern parts oceans: the western parts of the oceans are cold, where cold currents pass, and the eastern regions are warmed by warm currents.

Polar water masses . They form in the Arctic and near the coast and can be carried by currents to temperate and even tropical latitudes. The polar water masses are characterized by an abundance of floating ice, as well as ice that forms huge ice expanses. In the Southern Hemisphere, in areas of polar water masses, sea ice enters temperate latitudes much further than in the Northern Hemisphere. The salinity of the polar water masses is low, since floating ice has a strong desalination effect.

There are no clear boundaries between different types of water masses, differing in origin, but there are transition zones. They are most clearly expressed in places where warm and cold currents meet.

Water masses actively interact with: they give it moisture and heat and absorb carbon dioxide from it, release oxygen.

The most characteristic properties of water masses are And.

1. The concept of water masses and biogeographic zoning

1.1 Types of water masses

As a result of dynamic processes occurring in the oceanic water column, a more or less mobile water stratification is established in it. This stratification leads to the isolation of the so-called water masses. Water masses are waters characterized by their inherent conservative properties. Moreover, these properties are acquired by water masses in certain areas and retained within the entire space of their distribution.

According to V.N. Stepanov (1974) are distinguished: surface, intermediate, deep and bottom water masses. The main types of water masses can, in turn, be divided into varieties.

Surface water masses are characterized by the fact that they are formed by direct interaction with the atmosphere. As a result of interaction with the atmosphere, these water masses are most susceptible to: mixing by waves, changes in the properties of ocean water (temperature, salinity, and other properties).

The average thickness of the surface masses is 200-250 m. They are also distinguished by the maximum transfer intensity - on average about 15-20 cm/s in the horizontal direction and 10?10-4 - 2?10-4 cm/s in the vertical direction. They are subdivided into equatorial (E), tropical (ST and UT), subarctic (SbAr), subantarctic (SbAn), antarctic (An), and arctic (Ar).

Intermediate water masses stand out in the polar regions with elevated temperatures, in temperate and tropical regions - with low or high salinity. Their upper boundary is the boundary with surface water masses. The lower boundary lies at a depth of 1000 to 2000 m. Intermediate water masses are subdivided into subantarctic (PSbAn), subarctic (PSbAr), North Atlantic (PSAt), North Indian Ocean (PSI), Antarctic (PAn) and Arctic (PAR) masses.

The main part of the intermediate subpolar water masses is formed due to the subsidence of surface waters in the subpolar convergence zones. The transfer of these water masses is directed from the subpolar regions to the equator. In the Atlantic Ocean, the subantarctic intermediate water masses pass beyond the equator and are distributed up to about 20 ° N, in the Pacific - up to the equator, in the Indian - up to about 10 ° S. Subarctic intermediate waters in the Pacific also reach the equator. In the Atlantic Ocean, they quickly sink and get lost.

In the northern parts of the Atlantic and Indian Oceans, the intermediate masses have a different origin. They form on the surface in areas of high evaporation. As a result, excessively saline waters are formed. Because of their high density, these salty waters experience a slow sinking. To them are added dense salty waters from the Mediterranean Sea (in the North Atlantic) and from the Red Sea and the Persian and Oman Gulfs (in Indian Ocean). In the Atlantic Ocean, intermediate waters flow under the surface layer north and south of the latitude of the Strait of Gibraltar. They spread between 20 and 60°N. In the Indian Ocean, these waters spread south and southeast to 5-10°S.

The pattern of intermediate water circulation was revealed by V.A. Burkov and R.P. Bulatov. It is distinguished by an almost complete attenuation of wind circulations in the tropical and equatorial zones and a slight shift of subtropical circulations towards the poles. In this regard, intermediate waters from polar fronts spread to tropical and subpolar regions. The same circulation system includes subsurface equatorial countercurrents of the Lomonosov current type.

Deep water masses are formed mainly in high latitudes. Their formation is associated with the mixing of surface and intermediate water masses. They usually form on the shelves. Cooling and, accordingly, acquiring a greater density, these masses gradually slide down the continental slope and spread towards the equator. The lower boundary of deep waters is located at a depth of about 4000 m. The intensity of deep water circulation was studied by V.A. Burkov, R.P. Bulatov and A.D. Shcherbinin. It weakens with depth. In the horizontal movement of these water masses leading role play: southern anticyclonic gyres; circumpolar deep current in the southern hemisphere, which provides the exchange of deep water between the oceans. The horizontal movement speeds are approximately 0.2-0.8 cm/s, and the vertical ones are 1?10-4 to 7?10Î 4 cm/s.

Deep water masses are subdivided into: the circumpolar deep water mass of the Southern Hemisphere (GCP), the North Atlantic (GSAt), the North Pacific Ocean (GTS), the North Indian Ocean (GSI) and the Arctic (GAr). Deep North Atlantic waters are characterized by increased salinity (up to 34.95%) and temperature (up to 3°) and a slightly increased travel speed. The following are involved in their formation: waters of high latitudes, cooled on the polar shelves and sinking with the mixing of surface and intermediate waters, heavy salty waters of the Mediterranean, rather salty waters of the Gulf Stream. Their sinking intensifies as they move to higher latitudes, where they experience gradual cooling.

Circumpolar deep waters are formed exclusively due to the cooling of waters in the Antarctic regions of the World Ocean. The northern deep masses of the Indian and Pacific Oceans are of local origin. In the Indian Ocean due to the runoff of salt water from the Red Sea and the Persian Gulf. In the Pacific Ocean, mainly due to the cooling of waters on the shelf of the Bering Sea.

Bottom water masses are characterized by the lowest temperatures and the highest density. They occupy the rest of the ocean deeper than 4000 m. These water masses are characterized by very slow horizontal movement, mainly in the meridional direction. Bottom water masses are characterized by somewhat larger vertical displacements compared to deep water masses. These values ​​are due to the influx of geothermal heat from the ocean floor. These water masses are formed by lowering the overlying water masses. Among the bottom water masses, the bottom Antarctic waters (PrAn) are the most widespread. These waters are well traced by the lowest temperatures and relatively high oxygen content. The center of their formation is the Antarctic regions of the World Ocean and, in particular, the shelf of Antarctica. In addition, the North Atlantic and North Pacific near-bottom water masses (NrSat and NrST) are distinguished.

Bottom water masses are also in a state of circulation. They are characterized mainly by meridional transport in a northerly direction. In addition, in the northwestern part of the Atlantic, a southward current is clearly expressed, which is fed by the cold waters of the Norwegian-Greenland basin. The speed of movement of the bottom masses slightly increases when approaching the bottom.

1.2 Approaches and types of biogeographic classifications of water masses

The existing ideas about the water masses of the World Ocean, areas and reasons for their formation, transfer and transformation are extremely limited. At the same time, the study of all the diversity of water properties that occurs in real conditions is necessary not only to understand the structure and dynamics of waters, but also to study the exchange of energy and substances, the features of the development of the biosphere and other important aspects of the nature of the World Ocean.

Most of the intermediate, deep and near-bottom water masses are formed from surface ones. The sinking of surface waters occurs, as already mentioned, mainly due to those vertical movements that are caused by horizontal circulation. Especially favorable are the conditions for the formation of water masses at high latitudes, where the development of intense downward movements along the periphery of macrocirculation cyclonic systems is promoted by a higher density of water and its less significant vertical gradients than in the rest of the World Ocean. The boundaries of various types of water masses (surface, intermediate, deep and near-bottom) are boundary layers separating structural zones. Water masses of the same type, located within the same structural zone, are separated by oceanic fronts. They are much easier to trace near surface waters, where the fronts are most pronounced. It is comparatively easy to subdivide the intermediate waters, which noticeably differ in their properties from each other. It is more difficult to distinguish between different types of deep and bottom waters, given the homogeneity and still rather poor understanding of their movement. The attraction of new data (especially on the content of dissolved oxygen and phosphates in waters), which are good indirect indicators of water dynamics, made it possible to develop the previously developed general classification of the water masses of the World Ocean. At the same time, the study of water masses conducted by A.D. Shcherbinin. The water masses of the Pacific and Arctic Oceans have so far been less studied. On the basis of all available information, it was possible to refine the previously published schemes for the transfer of water masses in the meridional section of the oceans and to construct maps of their distribution.

Surface water masses.Their properties and limits of distribution are determined by the zonal variability of the exchange of energy and substances and the circulation of surface waters. The following water masses are formed in the surface structural zone: 1) equatorial; 2) tropical, subdivided into north-tropical and south-tropical, their peculiar modification is water Arabian Sea and the Bay of Bengal; 3) subtropical, dividing into northern and southern; 4) subpolar, consisting of subarctic and subantarctic; 5) polar, including Antarctic and Arctic. Equatorial surface water masses are formed within the equatorial anticyclonic system. Their boundaries are the equatorial and subequatorial fronts. They differ from other waters of low latitudes by having the highest temperature in the open ocean, minimum density, low salinity, oxygen and phosphate content, as well as a very complex system of currents, which, however, allows us to speak of the predominant transfer of water from west to east by the Equatorial countercurrent.

Tropical water masses are created in the tropical cyclonic macrocirculation system. Their boundaries are, on the one hand, tropical oceanic fronts, and on the other hand, the subequatorial front in the Northern Hemisphere, and the equatorial front in the Southern Hemisphere. In accordance with the prevailing rise of the waters, the thickness of the layer occupied by them is somewhat less than that of subtropical water masses, the temperature and oxygen content are lower, and the density and concentration of phosphates are somewhat higher.

The waters of the northern Indian Ocean are noticeably different from other tropical water masses due to the peculiar moisture exchange with the atmosphere. In the Arabian Sea, due to the predominance of evaporation over precipitation, high salinity waters up to 36.5 - 37.0‰ are created. In the Bay of Bengal, as a result of a large river runoff and an excess of precipitation over evaporation, water is strongly desalinated; salinity from 34.0-34.5‰ in the open part of the ocean gradually decreases to the top of the Bay of Bengal to 32-31‰. Consequently, the waters of the northeastern part of the Indian Ocean are closer in their properties to the equatorial water mass, while geographic location they are tropical.

Subtropical water masses are formed in subtropical anticyclonic systems. The boundaries of their distribution are tropical and subpolar oceanic fronts. In conditions of prevailing downward movements, they receive greatest development vertically. They are characterized by maximum salinity for the open ocean, high temperature and a minimum content of phosphates.

Subantarctic waters, determining the natural conditions of the temperate zone of the southern part of the World Ocean, take an active part in the formation of intermediate waters as a result of downward movements in the zone of the subantarctic front.

In macrocirculation systems, due to vertical movements, an intensive mixing of intermediate Antarctic waters with surface and deep waters occurs. In tropical cyclonic gyres, the transformation of waters is so significant that here it turned out to be expedient to single out a special, eastern, variety of the intermediate Antarctic water mass.

2. Biogeographic zoning of the World Ocean

2.1 Faunistic division of the littoral

Living conditions in the sea are determined by the vertical division of a given biocycle, as well as the presence or absence of a substrate for attachment and movement. Consequently, the conditions for the settlement of marine animals in the littoral, pelagic, and abyssal zones are different. Because of this, it is impossible to create a unified scheme for the zoogeographic zoning of the World Ocean, which is further aggravated by the very wide, often cosmopolitan distribution of most systematic groups of marine animals. That is why genera and species whose ranges have not been studied enough are used as indicators of certain regions. In addition, different classes of marine animals give a different pattern of distribution. Considering all these arguments, the overwhelming majority of zoogeographers accept the schemes for zoning marine fauna separately for the littoral and pelagic zones.

Faunistic division of the littoral. The faunistic division of the littoral is very clear, since certain areas of this biochore are quite strongly isolated both by land and climatic zones, and by wide stretches of the open sea.

They distinguish the central Tropical region and the Boreal regions located to the north of it, and to the south - the Antiboreal regions. In each of them, a different number of areas are distinguished. The latter, in turn, are subdivided into subregions.

Tropical region. This region is characterized by the most favorable conditions of existence, which led to the formation of the most complete harmoniously developed fauna here, which did not know breaks in evolution. The vast majority of classes of marine animals have their own representatives in the region. The tropical zone, according to the nature of the fauna, is clearly divided into two areas: Indo-Pacific and Tropical-Atlantic.

Indo-Pacific region. This area covers the vast expanse of the Indian and Pacific Oceans between 40 ° N. sh. and 40°S sh., and only off the western coast of South America, its southern border is sharply shifted to the north under the influence of a cold current. This also includes the Red Sea and the Persian Gulf, as well as countless straits between the islands.

Malay Archipelago and the Pacific Ocean. Favorable temperature conditions, due to the large area of ​​shallow waters, and the stability of the environment over many geological periods have led to the development of an exceptionally rich fauna here.

Mammals are represented by dugongs (genus Halicore) from the siren family, one species of which lives in the Red Sea, the other in the Atlantic, and the third in the Pacific Ocean. These large animals (3-5 m in length) live in shallow bays, abundantly overgrown with algae, and occasionally enter the mouths of tropical rivers.

Of the seabirds associated with the coasts, the Indo-Pacific region is characterized by small petrels and the giant albatross Diomedea exulans.

Hydrophiidae sea snakes are represented by a large number (up to 50) characteristic species. All of them are poisonous, many have adaptations for swimming.

Marine fish are extremely diverse. They are most often brightly colored, covered with multi-colored spots, stripes, etc. Of these, mention should be made of the symtomaxillary fishes - diodes, tetradons and bodyworks, Scaridae parrot fish, in which the teeth form a continuous plate and serve to bite off and crush corals and algae, as well as surgeon fish armed with poisonous spines.

Enormous development in the sea is achieved by coral reefs, consisting of thickets of six-ray (Madrepora, Fungia, etc.) and eight-ray (Tubipora) corals. Coral reefs should be considered the most typical biocenosis of the Indo-Pacific littoral. Numerous mollusks (Pteroceras and Strombus) are associated with them, distinguished by their brightly painted and diverse shells, giant tridacna weighing up to 250 kg, as well as holothurians that serve as a subject of fishing (they are eaten in China and Japan under the name trepang).

Of the marine annelids, we note the famous palolo. Its masses during the breeding season rise to the surface of the ocean; eaten by the Polynesians.

Local differences in the fauna of the Indo-Pacific region made it possible to distinguish in it the Indian-West-Pacific, East-Pacific, West-Atlantic and East-Atlantic subregions.

Tropical-Atlantic region. This area is much smaller in extent than the Indo-Pacific. It covers the littoral of the western and eastern (within the tropical Atlantic) coast of America, the waters of the West Indies archipelago, as well as the western coast of Africa within the tropical zone.

The fauna of this region is much poorer than the previous one, only the West Indian seas with their coral reefs contain a rich and varied fauna.

Sea animals here are represented by manatees (from the same sirenians), capable of going far into the rivers of tropical America and Africa. Of the pinnipeds, there are white-bellied seals, sea lions and the Galapagos seal. There are practically no sea snakes.

The fish fauna is diverse. It includes giant manta rays (up to 6 m in diameter) and large tarpon (up to 2 m in length), which is an object of sport fishing.

Coral reefs reach luxuriant development only in the West Indies, but instead of Pacific madrepores, species of the genus Acropora are common here, as well as hydroid corals Millepora. Crabs are extremely abundant and varied.

The littoral of the western coast of Africa is distinguished by the poorest fauna, almost devoid of coral reefs and associated coral fish.

The region is divided into two subregions - West Atlantic and East Atlantic.

boreal region. The region is located north of the Tropical Region and covers the northern parts of the Atlantic and Pacific Oceans. It is divided into three regions: Arctic, Boreo-Pacific and Boreo-Atlantic.

Arctic region. This area includes the northern coasts of America, Greenland, Asia and Europe, located outside the influence of warm currents (the northern shores of Scandinavia and the Kola Peninsula, heated by the Gulf Stream, remain outside the area). The Sea of ​​Okhotsk and the Bering Sea also belong to the Arctic region in terms of temperature conditions and composition of the fauna. The latter corresponds to the ecological zone, where the water temperature is kept at the level of 3-4 °C, and often even lower. For most of the year, ice cover remains here, even in summer ice floes float on the surface of the sea. The salinity of the Arctic Basin is relatively low due to the mass of fresh water brought by the rivers. Fast ice, typical for this area, prevents the development of the littoral in shallow waters.

The animal world is poor and monotonous. The most typical mammals are walruses, hooded seals, a polar or harp whale, a narwhal (a dolphin with a hypertrophied left canine in the form of a straight horn) and a polar bear, the main habitat of which is floating ice.

Birds are represented by gulls (primarily pink and polar), as well as guillemots.

The fish fauna is poor: cod cod, navaga and polar flounder are common.

Invertebrates are more diverse and numerous. The small number of crab species is offset by the abundance of amphipods, sea cockroaches and other crustaceans. Of the molluscs for Arctic waters, Yoldia arctica is typical, there are a lot of sea anemones and echinoderms. A feature of the Arctic waters is that starfish, hedgehogs and brittle stars live here in shallow waters, which in other zones lead a deep-sea lifestyle. In a number of regions, more than half of the littoral fauna consists of annelids sitting in calcareous tubules.

The uniformity of the fauna of this area throughout its entire length makes it superfluous to single out subregions in it.

Boreo-Pacific region. The area includes the coastal waters and shallow waters of the Sea of ​​Japan and the Pacific Ocean washing Kamchatka, Sakhalin and the northern Japanese Islands from the east, and in addition, the littoral of its eastern part - the coast of the Aleutian Islands, North America from the Alaska Peninsula to Northern California.

Ecological conditions in this area are determined by higher temperatures and their fluctuations depending on the time of year. There are several temperature zones: northern - 5-10°С (on the surface), middle - 10-15, southern - 15-20°С.

The Boreo-Pacific region is characterized by a sea otter, or a sea otter, eared seals - a fur seal, a sea lion and a sea lion, relatively recently there was a Steller's sea cow Rhytina stelleri, completely destroyed by man.

Of the fish, pollock, greenling and Pacific salmon are typical - chum salmon, pink salmon, chinook salmon.

Invertebrate littoral areas are diverse and abundant. They often reach very large sizes (for example, giant oysters, mussels, king crab).

Many animal species and genera of the Boreo-Pacific region are similar to representatives of the Boreo-Atlantic region or identical to them. This is the so-called phenomenon of amphiboreality. This term denotes the type of distribution of organisms: they are found in the west and east of temperate latitudes, but are absent between them.

Thus, amphiboreality is one of the types of rupture in the ranges of marine animals. This type of discontinuity is explained by the theory proposed by L.S. Berg (1920). According to this theory, the dispersal of boreal water animals through the Arctic basin occurred both from the Pacific Ocean to the Atlantic, and vice versa, in epochs when the climate was warmer than the present one, and the exit from the seas far north through the strait between Asia and America was carried out without hindrance. Such conditions existed at the end of the Tertiary period, namely in the Pliocene. In the Quaternary period, a sharp cooling led to the disappearance of boreal species in high latitudes, the zoning of the World Ocean was established, and continuous areas turned into broken ones, since the connection of inhabitants of moderately warm waters through the polar basin became impossible.

Auks, common seals, or spotted seals Phoca vitulina, many fish - smelt, gerbil, cod, and some flounders have an amphiboreal distribution. It is also characteristic of a number of invertebrates - some mollusks, worms, echinoderms and crustaceans.

Boreo-Atlantic region. The area includes most Barents Sea, Norwegian, Northern and Baltic Sea, the littoral of the eastern coast of Greenland and, finally, the northeast of the Atlantic Ocean south to 36 ° N. latitude. The whole area is under the influence of the warm Gulf Stream, so its fauna is mixed, and along with the northern ones, this includes subtropical forms.

The harp seal is endemic. Seabirds - guillemots, auks, hatchets - form giant nests (bird colonies). Of the fish, cod is common, among which endemic haddock is found. There are also numerous flounders, catfish, scorpions, gurnards.

Among the various invertebrates, crayfish stand out - lobster, various crabs, hermit crabs; echinoderms - red starfish, beautiful ophiura "jellyfish head"; Of the bivalves, mussels and cockles are widespread. There are many corals, but they do not form reefs.

The Boreo-Atlantic region is usually divided into 4 sub-regions: Mediterranean-Atlantic, Sarmatian, Atlanto-Boreal and Baltic. The first three include the seas of the USSR - the Barents, Black and Azov.

The Barents Sea is located at the junction of warm Atlantic and cold Arctic waters. In this regard, its fauna is mixed and rich. Thanks to the Gulf Stream, the Barents Sea has almost oceanic salinity and a favorable climate regime.

Its littoral population is diverse. Of the mollusks, edible mussels, large chitons, and scallops live here; from echinoderms - red starfish and urchin Echinus esculentus; from coelenterates - numerous sea anemones and sessile jellyfish Lucernaria; hydroids are also typical. Colossal accumulations are formed by the ascidian Phallusia obliqua.

The Barents Sea belongs to the high-feeding seas. The fishery of numerous fish is widely developed here - cod, sea bass, halibut, lumpfish. Of the non-commercial fish, spiny gobies, monkfish, and others live.

The Baltic Sea, due to its shallow water, limited connection with the North Sea, and also because of the rivers flowing into it, is heavily desalinated. The northern part of it freezes in winter. The fauna of the sea is poor and mixed in origin, since Arctic and even freshwater species join the Boreo-Atlantic ones.

The former include cod, herring, sprat and sea needle. Of the arctic species, one can name the slingshot goby and the crustacean sea cockroach. Freshwater fish include zander, pike, grayling and vendace. It is interesting to note the almost complete absence here of typical marine invertebrates - echinoderms, crabs and cephalopods. Hydroids are represented by Cordylophora lacustris, marine molluscs - by the sea acorn Valanus improvisus, mussel and edible cockle. There are also freshwater toothless, as well as barley.

Black and Sea of ​​Azov according to their fauna they belong to the Sarmatian subregion. These are typical inland water bodies, since their connection with the Mediterranean Sea is carried out only through the shallow Bosporus Strait. At depths below 180 m, the water in the Black Sea is poisoned with hydrogen sulfide and devoid of organic life.

The fauna of the Black Sea is exceptionally poor. The littoral zone is inhabited by mollusks. Here you can meet the saucer Patella pontica, black mussel, scallops, cockle and oyster; small hydroids, sea anemones (from coelenterates) and sponges. The lancelet Amphioxus lanceolatus is endemic. Of the fish, Labridae wrasses, Blennius blennies, scorpionfish, gobies, sultans, seahorses, and even two species of rays are common. Dolphins - puffers and bottlenose dolphins stay off the coast.

The mixed fauna of the Black Sea is expressed by the presence of a certain number of Mediterranean species along with the Black Sea-Caspian relics and species of freshwater origin. Mediterranean immigrants clearly predominate here, and the “mediterranization” of the Black Sea, as established by I.I. Puzanov continues.

Antiboreal region. South of the Tropical Region, similar to the Boreal Region to the north, is the Antiboreal Region. It includes the littoral of Antarctica and the subantarctic islands and archipelagos: South Shetland, Orkney, South Georgia and others, as well as the coastal waters of New Zealand, South America, southern Australia and Africa. It is along the Pacific coast of South America that, due to the cold southern current, the boundary of the Antiboreal region is pushed far to the north, up to 6 ° S. sh.

Based on the disunity of the littoral areas of the region, 2 areas are distinguished in it: Antarctic and Antiboreal.

Antarctic region. The area includes the waters of three oceans, washing the shores of Antarctica and located near the archipelagos. Conditions here are close to arctic, but even more severe. The floating ice boundary runs approximately between 60-50°S. sh., sometimes a little to the north.

The fauna of the region is characterized by the presence of a number of marine mammals: the maned sea lion, southern fur seal, true seals (leopard seal, Wedell seal, elephant seal). Unlike the fauna of the Boreal region, walruses are completely absent here. Of the birds of coastal waters, first of all, penguins should be mentioned, living in huge colonies along the shores of all the continents and archipelagos of the Antarctic region and feeding on fish and crustaceans. Particularly well known are the emperor penguin Aptenodytes forsteri and the Adélie penguin Pygoscelis adeliae.

The Antarctic littoral is very peculiar due to the large number of endemic species and genera of animals. As is often observed in extreme conditions, a relatively low species diversity corresponds to a huge population density. certain types. So, the pitfalls here are completely covered with clusters of the sedentary worm Cephalodiscus, in large numbers you can find crawling along the bottom sea ​​urchins, stars and holothurians, as well as accumulations of sponges. Amphipod crustaceans are very diverse, and about 75% of them are endemic. In general, the Antarctic littoral, according to the data of Soviet Antarctic expeditions, turned out to be much richer than could be expected, judging by the severe temperature conditions.

Both intertidal and pelagic animals of the Antarctic region include species that also live in the Arctic. This distribution is called bipolar. By bipolarity, as already noted, is meant a special type of disjunctive dispersal of animals, in which the ranges of similar or closely related species are located in polar or, more often, in moderately cold waters of the northern and southern hemispheres with a break in tropical and subtropical waters. When studying the deep-sea fauna of the World Ocean, it was found that organisms that were previously considered bipolar are characterized by a continuous distribution. Only within the tropical zone are they found at great depths, and in moderately cold waters - in the littoral zone. However, cases of true bipolarity are not uncommon.

To explain the reasons that caused the bipolar distribution, two hypotheses were proposed - relic and migration. According to the first, bipolar areas were once continuous and also covered the tropical zone, in which the populations of certain species became extinct. The second hypothesis was formulated by C. Darwin and developed by L.S. Berg. According to this hypothesis, bipolarity is the result of the ice age events, when cooling affected not only the Arctic and cold-temperate waters, but also the tropics, which made it possible for northern forms to spread to the equator and further south. The end of the ice age and the new warming of the waters of the tropical zone forced many animals to move out of its borders to the north and south or die out. In this way, gaps were formed. During their existence in isolation, the northern and southern populations managed to transform into independent subspecies or even close, but vicarious species.

Antiboreal region. The Antiboreal Region proper covers the coasts of the southern continents located in the transition zone between the Antarctic Region and the Tropical Region. Its position is similar to that of the Boreo-Atlantic and Boreo-Pacific regions in the northern hemisphere.

The living conditions of animals in this region are much better compared to the conditions of other regions, its fauna is quite rich. In addition, it is constantly replenished by people from the adjacent parts of the Tropical Region.

The most typical and richest is the antiboreal fauna of the South Australian subregion. Marine animals here are represented by southern fur seals (genus Arctocephalus), elephant seals, crabeater seals and leopard seals; birds - several species of penguins from the genera Eudiptes (crested and small) and Rugoscelis (P. papua). Invertebrates include endemic brachiopods (6 genera), worms Terebellidae and Arenicola, crabs of the genus Cancer, which are also found in the Boreo-Atlantic subregion of the northern hemisphere.

The South American subregion is characterized by the fact that its littoral antiboreal fauna is distributed along the coasts of South America far to the north. One of the seal species Arctocephalus australis and the Humboldt penguin reach the Galapagos Islands. The movement of these and many other marine animals to the north along the eastern coast of the mainland is facilitated by the Peruvian cold current and the rise of bottom waters to the surface. The mixing of water layers causes the development of a rich animal population. There are more than 150 species of decapods alone, and half of them are endemic. Cases of bipolarity are also known in this subdomain.

The South African subregion is small in area. It covers the Atlantic and Indian Ocean coasts South Africa. In the Atlantic, its border reaches 17 ° S. sh. (cold current!), and in the Indian Ocean only up to 24 °.

The fauna of this subregion is characterized by the southern fur seal Arctocephalus pusillus, the penguin Spheniscus demersus, a mass of endemic mollusks, from large crayfish - a special species of lobster Homarus capensis, numerous ascidni, etc.

2.2 Faunistic division of the pelagial

The open parts of the World Ocean, where life proceeds without connection with the substrate, are called pelagic. The upper zone of the pelagic zone (epipelagial) and the deep-water zone (batypelagial) are distinguished. The epipelagic zone is subdivided according to the uniqueness of the fauna into the Tropical, Boreal, and Antiboreal regions, which, in turn, are subdivided into a number of regions.

tropical region

The region is characterized by consistently high temperatures upper layers water. The annual amplitudes of its fluctuations do not exceed 2 °C on average. The temperature of the deeper layers is much lower. In the waters of the region, there is a rather significant species diversity of animals, but there are almost no huge accumulations of individuals of the same species. Many species of jellyfish, mollusks (pteropods and other pelagic forms), almost all appendicularians and salps are found only within the Tropical Region.

Atlantic region. This area is distinguished by the following characteristic features of the fauna. Cetaceans are represented by Bryde's minke whale, and mackerel, eels, flying fish, and sharks are typical of fish. Of the pleiston animals, there is a brightly colored siphonophore - a strongly stinging physalia, or a Portuguese man-of-war. A section of the tropical Atlantic called the Sargasso Sea is inhabited by a special community of pelagic animals. In addition to those already mentioned general characteristics seas of neuston inhabitants on free-floating sargasso algae are home to peculiar seahorses Hippocampus ramu-losus and needle fish, bizarre antennary fish (Antennarius mar-moratus), many worms and mollusks. It is noteworthy that the biocenosis of the Sargasso Sea is, in essence, a littoral community located in the pelagic zone.

Indo-Pacific region. The pelagic fauna of this area is characterized by the species of whale, the Indian minke whale Balaenoptera indica. However, there are other more widespread cetaceans here. Among the fish, attention is drawn to the sailboat Istiophorus platypterus, which is distinguished by its huge dorsal fin and the ability to reach speeds of up to 100-130 km / h; its relative, the swordfish (Xiphias gladius), with a sword-shaped upper jaw, also lives in the tropical waters of the Atlantic.

boreal region

This region combines cold and moderately cold waters of the Northern Hemisphere. On Far North most of them are covered with ice in winter, and even in summer individual ice floes are visible everywhere. Salinity due to the huge masses of fresh water brought by rivers is relatively low. The animal world is poor and monotonous. To the south, up to about 40 ° N. sh., stretches a strip of water, where their temperature fluctuates greatly and the animal world is relatively richer. The main area for the production of commercial fish is located here. The water area of ​​the region can be divided into 2 areas - Arctic and Euboreal.

Arctic region. The pelagic fauna of this area is poor, but very expressive. Cetaceans stand out in it: bowhead whale (Balaena mysticetus), fin whale (Balaenoptera physalus) and unicorn dolphin, or narwhal (Monodon monocerus). Fish include polar shark (Somniosus microcephalus), capelin (Mallotus villosus), which feed on gulls, cod and even whales, and several forms of eastern herring (Clupea pallasi). Clion mollusks and calanus crustaceans, breeding in huge masses, are the usual food of toothless whales.

Euboreal region. The pelagial region covers the northern parts of the Atlantic and the Pacific Ocean south of the Arctic region and north of the tropics. Temperature fluctuations in the waters of this area are very significant, which distinguishes them from arctic and tropical waters. Differences are observed in the species composition of the fauna of the boreal parts of the Atlantic and Pacific Oceans, but the number of common species is large (amphiboreal). The fauna of the Atlantic pelagial includes several species of whales (Biscay, humpback, bottlenose) and dolphins (pilot whale and bottlenose dolphin). Of the pelagic fish, the Atlantic herring Clupea harengus, mackerel, or mackerel, tuna Thynnus thunnus, not uncommon in other parts of the oceans, swordfish, cod, haddock, sea bass, sprat, and in the south - sardine and anchovy are common.

The giant shark Cetorhinus maximus is also found here, feeding on plankton, like baleen whales. Of the vertebrates of the pelagial, we note the jellyfish - the cockle and the cornerot. In the pelagial of the boreal part of the Pacific, in addition to amphiboreal species, whales live - Japanese and gray, as well as many fish - the Far Eastern herring Clupea pallasi, sardines (Far Eastern Sardinops sagax and Californian S. s. coerulea species), Japanese mackerel (Scomber japonicus) are common and king mackerel (Scomberomorus), from Far Eastern salmon - chum salmon, pink salmon, chinook salmon, sockeye salmon. Chrysaora and Suapea jellyfish, siphonophores, and salps are widespread among invertebrates.

Antiboreal region

To the south of the Tropical Region is the World Ocean Belt, which stands out as the Antiboreal Region. Like its counterpart in the north, it is also characterized by harsh environmental conditions.

The pelagic zone of this region is inhabited by a single fauna, since there are no barriers between the waters of the oceans. Cetaceans are represented by southern (Eubalaena australis) and pygmy (Saregea marginata) whales, humpback (Megaptera novaeangliae), sperm whale (Physeter catodon) and minke whales, which, like many other whales, migrate widely across all oceans. Among the fish, it is necessary to name bipolar ones - anchovy, sardine of a special subspecies (Sardinops sagax neopilchardus), as well as notothenia inherent only in the anti-boreal fauna - Notothenia rossi, N. squamifrons, N. larseni, which are of great commercial importance.

As in the littoral zone, the Antiboreal and Antarctic regions can be distinguished here, but we will not consider them, since the faunal differences between them are small.

3. Classification vertical structure related to the temperature of water masses and the content of living organisms in it

The aquatic environment is characterized by a lower heat input, since a significant part of it is reflected, and an equally significant part is spent on evaporation. Consistent with the dynamics of land temperatures, the water temperature has less fluctuations in daily and seasonal temperatures. Moreover, water bodies significantly equalize the course of temperatures in the atmosphere of coastal areas. In the absence of an ice shell, the sea in the cold season has a warming effect on the adjacent land areas, in summer it has a cooling and moisturizing effect.

The range of water temperatures in the World Ocean is 38° (from -2 to +36 °С), in fresh water - 26° (from -0.9 to +25 °С). The water temperature drops sharply with depth. Up to 50 m, daily temperature fluctuations are observed, up to 400 - seasonal, deeper it becomes constant, dropping to + 1-3 ° С (in the Arctic it is close to 0 ° С). Since the temperature regime in reservoirs is relatively stable, their inhabitants are characterized by stenothermy. Minor temperature fluctuations in one direction or another are accompanied by significant changes in aquatic ecosystems.

Examples: a “biological explosion” in the Volga delta due to a drop in the level of the Caspian Sea - the growth of lotus thickets (Nelumba kaspium), in southern Primorye - the overgrowth of calla oxbow rivers (Komarovka, Ilistaya, etc.) along the banks of which woody vegetation was cut down and burned.

Due to the different degree of heating of the upper and lower layers during the year, ebbs and flows, currents, storms, there is a constant mixing of the water layers. The role of water mixing for aquatic inhabitants (hydrobionts) is exceptionally great, since at the same time the distribution of oxygen and nutrients inside the reservoirs is leveled, providing metabolic processes between organisms and the environment.

In stagnant water bodies (lakes) of temperate latitudes, vertical mixing takes place in spring and autumn, and during these seasons the temperature in the entire water body becomes uniform, i.e. comes homothermy.In summer and winter, as a result of a sharp increase in heating or cooling of the upper layers, the mixing of water stops. This phenomenon is called temperature dichotomy, and the period of temporary stagnation is called stagnation (summer or winter). In summer, the lighter warm layers remain on the surface, being located above the heavy cold ones (Fig. 3). In winter, on the contrary, the bottom layer has warmer water, since directly under the ice the surface water temperature is less than +4 °C and, due to the physicochemical properties of water, they become lighter than water with a temperature above +4 °C.

During periods of stagnation, three layers are clearly distinguished: the upper layer (epilimnion) with the sharpest seasonal fluctuations in water temperature, the middle layer (metalimnion or thermocline), in which there is a sharp jump in temperature, and the near-bottom layer (hypolimnion), in which the temperature changes little during the year. During periods of stagnation, oxygen deficiency forms in the water column - in the summer in the bottom part, and in the winter in the upper part, as a result of which fish kills often occur in winter.

Conclusion

Biogeographic zoning is the division of the biosphere into biogeographic regions, reflecting its basic spatial structure. Biogeographic zoning is a section of biogeography that summarizes its achievements in the form of schemes for a general biogeographic division. Biogeographic zoning division considers biota as a whole as a set of floras and faunas and their biocenotic territorial complexes (biomes).

The main variant (basic) of universal biogeographic zoning is the natural state of the biosphere without taking into account modern anthropogenic disturbances (deforestation, plowing, catching and extermination of animals, accidental and intentional introduction of alien species, etc.). Biogeographic zoning is developed taking into account the general physical and geographical patterns of the distribution of biota and their regional historically isolated complexes.

In this term paper the methodology of biogeographic zoning of the World Ocean was considered, as well as the stages of biogeographic research. Summing up the results of the work performed, it can be concluded that the goals and objectives were achieved:

The methods of researching the World Ocean were studied in detail.

The zoning of the World Ocean is considered in detail.

The studies of the World Ocean are studied in stages.

Bibliography

1.Abdurakhmanov G.M., Lopatin I.K., Ismailov Sh.I. Fundamentals of Zoology and Zoogeography: Textbook for students. higher ped. textbook establishments. - M.: Publishing Center "Academy", 2001. - 496 p.

2.Belyaev G.M., Bottom fauna of the greatest depths (ultraabyssals) of the world ocean, M., 1966

.Darlington F., Zoogeography, trans. from English, M., 1966

.Kusakin O.G., On the fauna of Isopoda and Tanaidacea in the shelf zones of Antarctic and subantarctic waters, ibid., v. 3, M. - L., 1967 [v. 4(12)]

.Lopatin I.K. Zoogeography. - Mn.: The highest school, 1989

.Pacific Ocean, v. 7, book. 1-2, M., 1967-69. Ekman S., Zoogeography of the sea, L., 1953.

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Water masses are large volumes of water that form in certain parts of the ocean and differ from each other in temperature, salinity, density, transparency, the amount of oxygen contained, and many other properties. Unlike air masses, vertical zonality is of great importance in them. Depending on the depth, the following types of water masses are distinguished:

Surface water masses. They are located to a depth of 200-250 m. The water temperature and salinity often change here, since these water masses are formed under the influence of precipitation and the influx of fresh continental waters. Waves and horizontal ocean currents form in surface water masses. In this type of water masses, the highest content of plankton and fish.

Intermediate water masses. They are located to a depth of 500-1000 m. Basically, this type of mass is found in the tropical latitudes of both hemispheres and is formed under conditions of increased evaporation and a constant increase in salinity. Deep water masses. Their lower limit can reach up to 5000 m. Their formation is associated with the mixing of surface and intermediate water masses, polar and tropical masses. Vertically, they move very slowly, but horizontally - at a speed of 28 m / h.

Bottom water masses. They are located in the World Ocean below 5000 m, have a constant salinity and a very high density.

Water masses can be classified not only by depth, but also by origin. In this case, the following types of water masses are distinguished:

Equatorial water masses. They are well warmed by the sun, their temperature varies by season by no more than 2° and is 27 - 28°C. They are desalinated by abundant precipitation and rivers flowing into the ocean in these latitudes, so the salinity of these waters is lower than in tropical latitudes.

Tropical water masses. They are also well warmed by the sun, but the water temperature here is lower than in the equatorial latitudes, and is 20-25°C. Seasonally, the temperature of the waters of tropical latitudes varies by 4 °. The temperature of the waters of this type of water mass is greatly influenced by ocean currents: the western parts of the oceans, where warm currents come from the equator, are warmer than the eastern ones, since cold currents come there. The salinity of these waters is much higher than that of the equatorial ones, since here, as a result of descending air currents, high pressure is established and little precipitation falls. Rivers also do not have a desalination effect, since there are very few of them in these latitudes.

Moderate water masses. Seasonally, the temperature of the waters of these latitudes differs by 10°: in winter, the water temperature ranges from 0° to 10°C, and in summer it varies from 10° to 20°C. For these waters, the change of seasons is already characteristic, but it comes later than on land, and is not so pronounced. The salinity of these waters is lower than that of tropical waters, since atmospheric precipitation, rivers flowing into these waters, and icebergs entering these latitudes have a desalination effect. Temperature differences between the western and eastern parts of the ocean are also characteristic of moderate water masses: the western parts of the oceans are cold, where cold currents pass, while the eastern regions are warmed by warm currents.

Polar water masses. They form in the Arctic and off the coast of Antarctica and can be carried by currents to temperate and even tropical latitudes. The polar water masses are characterized by an abundance of floating ice, as well as ice that forms huge ice expanses. In the Southern Hemisphere, in areas of polar water masses, sea ice enters temperate latitudes much further than in the Northern Hemisphere. The salinity of the polar water masses is low, since floating ice has a strong desalination effect.

Between different types of water masses, differing in origin, there are no clear boundaries, but there are transitional zones. They are most clearly expressed in places where warm and cold currents meet. Water masses actively interact with the atmosphere: they give it moisture and heat, absorb carbon dioxide from it, and release oxygen. The most characteristic properties of water masses are salinity and temperature.