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the study of water populations, their interrelations with habitat and significance for the transformation of energy and matter, and the biological productivity of the ocean, seas, and inland waters.
Hydrobiology is primarily an ecological science. The living conditions in water are determined by the physicogeographic characteristics of the body of water. Many of these features—for example, the chemical composition of the water (in particular, the composition and amount of biogenic elements and dissolved gases, the nature of bottom sediments, and the transparency of the water)—are strongly influenced by aquatic organisms and are often determined by their life processes. Therefore, to the extent to which hydrobiology studies the role of living phenomena in the context of the aggregate of interdependent processes of the aquatic medium, it has problems in common with the combined disciplines of limnology and oceanography. Such matters as the biological structure of the ocean, the bio-limnological and bio-oceanological typology of bodies of water and water masses, and the regular patterns of the recycling of substances and the flow of energy are treated at this level of research.
Hydrobiology is greatly concerned with establishing a scientific basis for the rational exploitation of biological resources of the waters. This is bound up in many ways with the requirements of the marine and freshwater fishing industries, farm pond fishery, and the use of aquatic invertebrates and mammals (food-fish hydrobiology). Other practical applications of hydrobiology and stimuli to its development are the biological questions related to the use of the continental surface fresh water for drinking purposes and industrial supply, the protection of natural water against pollution, the self-purification of polluted water, and the biological methods of treating waste waters (sanitary hydrobiology). Hydro-biological methods are used to evaluate the extent of water pollution through the presence of certain indicator organisms (the so-called biological analysis of water quality). Hydrobiology studies the role of aquatic organisms as agents of self-purification. The concerns of technical hydrobiology are the related problems pertaining mainly to biological interference with the water supply and operation of ships (for example, the fouling by microorganisms and sessile animals of the hulls of ships, various apparatus and hydraulic structures, and the pipes and water supply lines of electrothermal power plants; the overgrowth of aquatic plants in reservoirs, and the damage to ships and port installations by wood borers and rock borers). New problems continue to arise, such as the need to determine the effect of plankton on the absorption and scattering of sound—information indispensable to specialists in underwater acoustics. Navigational hydrobiology is the study of biological interference (for example, bioluminescence) with naval activities; agricultural hydrobiology includes the study of the role of hydrobionts in the fertilization of rice paddies and the possibilities of fish breeding in these waters.
The natural communities of aquatic organisms that constitute the water population did not receive systematic study until the latter part of the 19th century. This study led to the eventual separation of hydrobiology from botany and zoology, which had long been engaged in the study of both terrestrial and aquatic organisms. Of great importance to the progress of hydrobiology as a science with its own objects of study, methods, and tasks were the first quantitative investigations of plankton (chiefly tiny water-dwelling organisms and a life-form specific to the aquatic environment), initiated in the 1880’s by the German scientist W. Hansen. Using the example of Kiel Bay, he showed the need for quantitative data on plankton as a source of food for commercial fish and as the basis of the biological productivity of the sea. Quantitative studies were subsequently begun on benthos, organisms that live at the bottom of bodies of water (again primarily for the sake of promoting the fishing industry). The quantitative study of benthos became widespread after bottom grabs (sample-taking devices) came into use; these were first suggested for marine research in 1911 by the Danish scientist C. Petersen and for freshwater studies by the Swedish scientist S. Eckmann.
Quantitative methods for investigating natural communities of aquatic organisms in order to determine the number (density) of individuals of various species and their biomass have received very broad attention in hydrobiology. Many specialized hydrobiological devices, such as plankton nets, plankton catchers, plankton samplers, and bottom grabs of various design, are used for this purpose.
In addition to the plankton and benthos, investigators have identified such characteristic aquatic forms as the nekton (the larger free-swimming animals that are capable of resisting the current, such as fish and squid), the neuston (communities of animals and plants characteristically of the surface of the water), the pleuston (semiaquatic submerged organisms), the epineuston (organisms that skim over or lie upon the surface film), and the hyponeuston (organisms that live under the surface film but remain in close contact with it). The com-minities of organisms living on the surface of submerged objects are called periphytons or epibionts.
The first, primarily floristic, faunistic, and biogeographical state in hydrobiological research arose from the need to study the composition and distribution of the species of organisms populating the seas and inland waters. This task, especially in regard to less known regions and taxonomic groups, is still important. A great deal of work has been done on the composition of freshwater and sea populations, the material having been collected chiefly through expeditions. The English marine expedition on the Challenger (December 1872 to May 1876) was of exceptional importance in laying the foundation for the study of life at great depths. Beginning in the last quarter of the 19th century marine and freshwater biological stations were organized in a number of countries, thereby creating new opportunities for thorough, year-round hydrobiological research.
Soviet hydrobiology makes extensive use of both expeditions and research at permanent stations. Of great significance in the development of freshwater hydrobiology was the work of V. M. Arnol’di, A. L. Bening, G. Iu. Ve-reshchagin, V. N. Voronkov, V. I. Zhadin, S. G. Lepneva, V. M. Rylov, and D. O. Svirenko, as well as the research carried out in the 1920’s and 1930’s at the Kosino and Lake Glubokoe biological stations near Moscow (by L. L. Ros-solimo, S. I. Kuznetsov, G. G. Vinberg, E. V. Borutskii, and G. S. Karzinkin) and at the Baikal biological station of the University of Irkutsk (by M. M. Kozhov).
The foundations of Russian marine hydrobiological research were laid as early as the first decade of the 20th century by the scientific and commercial marine expeditions of N. M. Knipovich and the work of S. A. Zernov and K. M. Deriugin. This has been developed most widely in the Soviet period, beginning with the work done on the Barents Sea in the 1920’s under the direction of I. I. Mesiatsev and L. A. Zenkevich at the Floating Marine Research Institute (created through a 1921 decree signed by V. I. Lenin). The great achievements of Soviet marine hydrobiology (V. G. Bo-gorov, V. A. Vodianitskii, E. F. Gur’ianova, P. I. Usachev, A. A. Shorygin, and V. A. Iashnov), which were summarized in a book by L. A. Zenkevich (1963), enjoy worldwide recognition. Especially significant were the results of the work done in the Pacific and Indian oceans on the Vitiaz’ (beginning in 1949), in Antarctic waters on the Ob’, in the Atlantic Ocean on the M. Lomonosov, and on other research vessels, which established a clearer picture of biological structure and productivity. Extensive material was collected on the taxonomy and distribution of the fauna and flora of the world’s oceans.
As information accumulated on the composition of aquatic populations, attention was focused on elucidating the ecological conditions under which particular biocenoses and habitats of individual species of aquatic organisms were formed. This stage in the history of hydrobiology is reflected in S. A. Zernov’s General Hydrobiology (1934; 2nd ed., 1949), a major contribution to Soviet hydrobiology.
Much attention is devoted to furthering the understanding of the importance of biological phenomena in the classification of natural waters, as well as to the theory of biological productivity, the patterns of the biotic cycle, and the flow of energy in aquatic communities.
The next task of hydrobiological research is to clarify the function of aquatic organisms in the processes at work in their environment. This information is needed in order to control biological productivity and self-purification as well as to make rational use of biological resources. The functional characteristics of aquatic organisms can be determined only by experimental investigations of their metabolism, growth, nutrition, and chemical and biochemical composition. The work of N. S. Gaevskaya, V. S. Ivlev, and S. N. Skadovskii has had a major impact on this phase of Soviet hydrobiology.
The solution of a number of hydrobiological problems often requires research at the most varied levels—from the molecular, cellular, and organismic to the populational and biocenotic. For example, to determine the causes of excessive development of phytoplankton (so-called water-bloom), it is necessary to take into account both the interaction of different algal and microbial species through specific metabolites excreted into the water and the cycle of biogenic elements (for example, nitrogen and phosphorus). This cycle depends upon the properties of the body of water as a whole and upon the runoff from its drainage basin.
The regular pattern of the interdependence of all phenomena in a body of water, which is an integrated natural object, was emphasized at the turn of the century in the classic works of the Swiss limnologist F. Forel. In the 1920’s, A. Thienemann of Germany and E. Naumann of Sweden demonstrated the possibility of subdividing lakes, as well as other bodies of water, into biolimnological types (for example, into oligotrophic and eutrophic). The problems of typology and the classification of natural bodies of water are still under study.
The great complexity and heterogeneity of the natural phenomena with which hydrobiology deals have led to the use of many research techniques. Examples of these techniques include measurement through radioactive carbon of the intensity of plankton photosynthesis (proposed by the Danish scientist E. Stiemann-Nielson), a method which already has yielded data for gauging the primary production of the ocean and of the hydrosphere as a whole; spectrophotometric methods of determining the chlorophyll content of plankton; and methods of studying the role of aquatic bacteria (principally by the Soviet scientists E. L. Isachenko, V. S. Butkevich, A. S. Razumov, S. I. Kuznetsov, Iu. and I. Sorokin). Sampling and observation in connection with marine and some freshwater hydrobiological research are aided by aqualungers; underwater television and photography are used at great depths, and the distribution of plankton and other aquatic organisms is traced with the help of echo-sounding devices. The latest physical methods are used in the study of deep-sea bioluminescence and to gain an understanding of the interconnections between the processes at work in aquatic ecosystems. Mathematical simulation and electronic computers are also employed.
The growing influence of theoretical studies upon the solution of practical problems is characteristic of hydrobiology, especially in the USSR. Hydrobiological knowledge and methods are widely used to evaluate food reserves of bodies of water as bases for their fish yield. These methods are also used in commercial prospecting and in fish breeding. The great progress of hydrobiology in the USSR has made it possible to begin to influence the biological productivity of bodies of water. Before the war, L. A. Zenkevich directed experimental work on enriching the bottom fauna of the Caspian Sea, to which the polychaete worm Nereis, an important source of food for sturgeon, was introduced. Organisms used as food (chiefly crustaceans, such as mysids) have been successfully adapted to many reservoirs and some lakes (for example, Lake Balkhash). As a result of hydrobiological research, new methods have been proposed for increasing the fish yield of ponds through the addition of inorganic fertilizers. These fertilizers are now regularly used in pond fish farming, the productivity of which has thereby been greatly increased.
The field of sanitary hydrobiology studies the effect upon aquatic organisms and their communities of the toxic substances in industrial effluent, the mechanism of the biological self-purification of water, and other matters relating to the pressing problem of supplying man’s growing need for pure water.
Research on the inland waters of the USSR is conducted by the Institute of the Biology of Inland Waters and the Institute of Zoology, both of the Academy of Sciences of the USSR; the Institute of Hydrobiology of the Academy of Sciences of the Ukrainian SSR; the Institute of Limnology of the Siberian division of the Academy of Sciences of the USSR; and the State Scientific Research Institute of Lake and River Fisheries. The universities of Moscow, Kazakhstan, Saratov, Byelorussia, and Irkutsk, as well as a number of other institutions, are also involved in the study of inland waters. These studies, particularly those of Lake Baikal, the Caspian Sea, the Aral Sea, and reservoirs on the Volga, Dnieper, and other rivers have led to important results. The Academy of Sciences of the Ukrainian SSR has published the Gidrobiologicheskii zhurnal (Kiev) since 1965.
Broad-scale research in marine hydrobiology is conducted by the Institute of Oceanography of the Academy of Sciences of the USSR; the Institute of Biology of the Southern Seas of the Academy of Sciences of the Ukrainian SSR; the All-Union Institute of Marine Fishing and Oceanography and its field institutes—the Pacific (in Vladivostok), Arctic (Murmansk), Atlantic (Kaliningrad), and Azov-Black Sea scientific research institutes of marine fishing and oceanography; the Institute of Zoology of the Academy of Sciences of the USSR; and universities (for example, of Leningrad and Odessa) and other institutions.
The most important international organizations concerned with hydrobiology are the permanent International Council for the Exploration of the Sea (Copenhagen), which publishes the Journal de Conseil (since 1926), and the International Association of Theoretical and Applied Limnology, which was founded in 1922 and regularly sponsors congresses of limnologists (the 18th congress was held in 1971). The oldest international journal of hydrobiology is the Archiv für Hydrobiologie (Stuttgart, since 1906). Other publications include the Internationale Revue der gesamten Hydrobiologie und Hydrographie (Leipzig, since 1908) and Limnology and Oceanography (USA, since 1956).
REFERENCESZhizn’ presnykh vod SSSR, vols. 1-4. Moscow, 1940-59.
Zhadin, V. I. Metody gidrobiologicheskogo issledovaniia. Moscow, 1960.
Zenkevich, L. A. Fauna i biologicheskaia produktivnost’ moría, vol. 1. Moscow, 1951. Zenkevich, L. A. Biologiia morei SSSR. Moscow, 1963.
Zenkevich, L. A. “Izuchenie fauny morei i okeanov.” In Razvitie biologii v SSSR. Moscow, 1967.
Vinberg, G. G. Gidrobiologiia presnykh vod. Moscow, 1967.
Konstantinov, A. S. Obshchaia gidrobiologiia. Moscow, 1967.
G. G. VINBERG