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Marine resources include biotic, mineral and energy resources. The fertility of the sea is determined by oceanic circulation, biological processes of uptake and mineralization, settling of organic debris and regeneration of nutrients, migration of animals and the nutrient supply from land. The deep water of the Pacific and Indian Ocean is three times higher in nutrients than the Atlantic. The circulation of the north Pacific forms a trap for nutrients. The flora and fauna of the sea are immensely varied although they represent 16% of all species in the world. The phytoplankton are the minute plants on which all the other marine creatures depend for their living. Many of them are diatoms. Fertility based only on nutrient supply would be expected to be low and constant in the Tropics, low in summer but high in winter at 40 degrees and considerably higher all through the year at 60 degrees. Zoo plankton depends for its food on the phytoplankton. Two broad divisions of fauna are the epipelagic (on the continental shelf) and the bathypelagic of the deep ocean. Epipelagic fauna are coral reefs and mangrove swamp communities. Fish of different types occupy all depth zones, from euphotic zone to twilight zone (up to 1000 in).

The organisms that live on the bottom of the sea are the benthos. Benthos are an important means whereby the finely divided food on the ocean floor is made available for predator. Benthos also prey on some of the bottom living fish. Fish were not the only predators, some of them being eaten by carnivores. These carnivores compete with man for the demersal or bottom living fish. Another important benthic fauna includes crabs, shrimps and lobsters. The demersal fish that live near the bottom of the sea can be divided into two broad types such as round type (cod, haddock and hake) and the flat type (plaice, sole and halibut). Pelagic fish includes herring, sardine and others. Similarly to the environment in which fish live, their migration is important. Availability of plankton, currents tides and local river currents determine the movement of fish. Commercially important migratory species includes herring, salmon, cod, plaice and eels. Among the marine mammals whales are commercially important All these organic production of the sea is derived ultimately from the phytoplankton. It is more economical to catch and use animals or even plants having a fairly short food chain, such as the whales and the herrings. The limit to the harvest of the sea is set by the primary productivity of the ocean. The most fertile areas are the upwalling zones (180-360 g degrees/meter sq./year). All oceans estimated mean is 50 g degrees/meter sq./year).

The continued increase of human population is the basic reason for the biological exploitation of the oceans. Political and commercial factors determine the depth of exploitation. The fish catch and the arable land when it is related as a proportion show the dependency of the country on the sea for food. Japan, Vietnam and Korea show high dependency on the sea among all nations of the world. The major fisheries are the Grand Bank, the Dogger banks and the Sea of Japan which are well developed. Among the tropical lands, Peru has developed the fisheries and it is the leading producer at present.

Increasing demand for fish leads to over exploitation. It has been estimated that 20% of the net primary production of the ocean provided food for humans. Most of the. experts believe that everything possible is already being harvested from the sea. There is a loss of 80-90% at each step in the food chain and that the maximum sustainable harvest is done. On certain fish stock biological value has been depleted seriously by overfishing - a decrease in average size of fish caught, a decrease in average weight of the total catch and increasing wastage of energy. Whales and seals have been reduced to near extinction levels. Demersal bottom living fish are susceptible to overkill. If the biological productivity of the ocean is to be maintained, a sustained yield is to be maintained. Protected breeding in marine farms are undertaken. Since the oceans are an 'open pool' or common resource, successful conservation depends on a very high degree of international co-operation.

Apart from the biotic resources, the ocean supplies a small proportion of Chemical and Geological resources. Minerals that are economically worth mining from the sea are relatively few. The entire production amounts to one-tenth of the minerals mined on land. Potential resources include phosporite (eastern USA, off the coast of southern California, N.W. Mexico, Peru-Chile, and S. Africa). Manganese nodules have been found widely in the Pacific. Sand and gravel are abundant. By far the most important mineral production is that of oil and gas. By 1980, it was estimated that one third of the world oil production would be offshore. Salt productions amounts to 35 million tons per year. The greatest potential lies in desalinization to obtain fresh water.

The problems created by man in polluting the ocean are manifold. Sewage disposal is the cause for the decrease of light penetration affecting biological cycle in the oceans. The residue from chlorinated hydrocarbons (DDT cannot be reduced by the marine bacteria, therefore it contaminates the environment). There is every likelihood of spreading heavy metal pollution and mercury is very toxic pollutant. They are the causes for the death of fish population. Oil pollution is widespread and destroys the benthic fauna and other shore life. The microbiology is closely linked with oil pollution. The disposal of plastic and other less soluble waste disturbs the natural balance of the ecosystem. All these problems are presenting alarming picture, therefore conservation and prevention are necessary. This is possible only by international co-operation.

The interaction of man with his environment is growing and there is always a need to understand ecosystem. This knowledge is necessary as man tends to over exploit in all fields facing critical problems of imbalances.

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