IMPACT OF POLLUTION ON AQUATIC RESOURCES

Akansha Bisht and Grishma Tewari

College of Fisheries

G. B. Pant University of Agriculture and Technology, Pantnagar, Uttarakhand, India

Aquatic resources are fundamental to livelihood of man and they are a vital component in the well being of all living organisms be it plants or animals. Aquatic resources are the resources that take their source from water. They are useful or potentially useful to humans, which may be in agricultural, industrial, household, recreational, research, navigation, health and environmental activities. Virtually all of these human uses require freshwater. About 97.5% of water on the earth is salt water, leaving only 2.5% as freshwater. Water resources demand already exceed supply in the world and as world population continues to rise at an unprecedented rate, many more imbalances should be expected in the supply of aquatic resources.

The human population along the coastal area is 25% of the total population and population intensity along the coastal region increases pressure on the utilization of resources leading to habitat destruction, degradation and fragmentation, and the exponential growth of human population and progressive industrialization are posing serious threats to aquatic environment and its resource potential.

The major components of coastal zone are the coastal waters and the coastal land regime, which are subjected to intense pollution by diverse means. The pollutants in aquatic environment are diverse and complex in nature and the main sources of pollution in Indian coasts are through effluent discharge from industries, pesticide leaching from agricultural fields, oil spills from oil tankers and boats, sewage and waste disposal and retting of coconut husk along estuaries and backwaters.

According to reports more than 90% of the industries in India do not have adequate facilities to treat the effluents and as a result huge quantities of untreated effluents containing chemicals and wastes are discharged into the aquatic environment leading to serious consequences in the environment.

Pollution in water body reduces biodiversity of organisms in the water leaving only those organisms that can tolerate the pollutants and their effects. Aquatic plants are very important in aquatic system in so many ways which include-
- Production of oxygen for the water organisms through photosynthesis
- Provision of food for aquatic organisms (primary producers)
- Direct or indirect provision of shelter for fish and invertebrates
- Consolidation of river bed and banks
- Marginal plants provide resting sites and food source for waste birds
- Provision of aesthetic appeal to water body
- Provision of spawning medium for some fishes.

These important plants species are often exploited by human activities like- encroachment, navigation, construction, boating and even fishing and cultural purposes. When this problem of poor exploitation occur the animals depending on those plants species are affected due to the low production of primary producers to produce food for the animals and eventually result in low aquatic productivity. On the other hand, plants population increases in some aquatic environment due to their proximity to sewage effluent and agricultural practices (fertilization) that release nutrients (nitrogen and phosphorous) to the water through runoffs. This causes increase in the growth of aquatic weeds and algae bloom that often cause fish kills and inhibit the growth of other animals in the water.

Occurrence of fish kills and migration of fish from polluted areas becomes a regular feature. The Hoogly estuary of West Bengal was once considered as the spawning ground for the Hilsa fish but it is not so at present due to environmental degradation. Episodes of fish kills have been reported from Trombay basin and Periyar estuary of Kerala. Reduced fish productivity, mass destruction of aquatic flora and fauna, especially as a result of industrial toxicants has been reported.

Many externally visible diseases are prevalent in fish population and their incidences have been proposed as an index of pollution. Comparative toxicity of various pollutants on aquatic organisms under controlled laboratory conditions has been assessed and it is reported that at lower concentrations, the toxic materials may not cause the death of the organisms. However, they may cause stress to the organisms by interfering with the normal physiological functions. There are several experimental studies on the sub-lethal effects of pollutants. A wide array of responses due to sub-lethal effects have been reported and they are changes in swimming performance, respiration, phototaxis, equilibrium, decreased heart rate, delayed embryonic development, disrupted liver function, biomagnifications, blood chemistry alteration, behavioural changes and tissue damage.

The toxic materials may accelerate detrimental effects either directly or indirectly on the organisms in question. Due to the development of more industries, increased urbanization and reclamation of areas, the environment is under severe stress and these create an unfavourable situation for aquatic organisms to live. The pollutants can weaken the organisms making it susceptible to disease or they cause disease directly. Toxicants or other stressful situations may enhance the disease.

A correct assessment of the impact of various kinds of pollutants on the onset of diseases in fish is of prime importance in fisheries management. A proper monitoring of coastal pollution and enforcement of strict measures to control pollution would help enhancing the productivity of the coastal environment.

The challenge of conservation and management of aquatic resources is to understand the complex connections among aquatic resources and balance resources with protection to ensure an adequate supply for the future usages. Aquatic resources must be conserved and managed for their biological, economic and recreational values, as well as their natural beauty and importance to local cultures. In order to accomplish this goal, a variety of conservation and management methods are used. These include reducing consumption of resources; protecting them from contamination or pollution; recycling resources when possible; and fully protecting, or preserving resources.

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Michael J. Kennish (1998). Pollution impacts on marine biotic communities. CRC Press.