Organisms . Water pollution can be lethal to aquatic organisms and others that depend on these water bodies. Accidental oil spills from tanker ships can cause substantial environmental damage. Oil spreads on the water surface, prevents the entry of light and oxygen into the water.
This increases BOD and COD, resulting in mass Leaks and Spills: This occurs mostly due to ship collision, off shore oil rigs, oil leakages and discharges into sea (Fig. . c). Sources of water pollution can also be classified in three ways.
They are municipal wastes, industrial wastes, and agricultural wastes. Sources of water pollution Municipal wastes Industrial wastes Agricultural wastes . Municipal waste water is from homes and commercial establishments. .
Industrial discharge (effluents) may contain varieties of compounds such as heavy metals (cadmium, chromium, lead), and organic / inorganic chemicals Fig . Sources of water pollution (a) (b) (c) XII Std Biology-Zoology Chapter- XII Std Biology-Zoology Chapter- Environmental Issues death of organisms and degradation of water quality. It also clogs fish gills and the feathers of aquatic birds. On January , , two cargo ships collided off the Ennore coast in Chennai causing oil to spill into the sea.
Due to wave action and the southern current, the spill spread over to km down south affecting the coast. Beach sand also got spoiled by the oil sludge. It took more than a thousand volunteers to clean the oil sludge. .
Humans and other organisms can get affected by diseases such as hepatitis and typhoid by consuming contaminated water and food. Excess of fluoride in drinking water causes fluorosis. In many poor nations, outbreak of water borne diseases and epidemics are a result of contaminated water and poor or absence of water treatment processes. .
Water pollution can cause eutrophication due to nutrient enrichment. This causes algal blooms which affect the quality of water bodies (Fig. . ) .
Red tides, if occur, can be lethal to aquatic organisms. Fig. . Algal bloom