Effect of Water pollution on Organisms

Water pollution can be directly lethal to aquatic organisms and to any other organism that depends on the affected water body. Three specific harms are described. First, oil leaks and spills -- occurring mainly from ship collisions, offshore rig accidents, and discharge into the sea -- spread as a film on the water surface, blocking light and oxygen from entering the water; this raises Biochemical Oxygen Demand (BOD) and Chemical Oxygen Demand (COD), causing mass death of organisms and general degradation of water quality, and also clogs fish gills and the feathers of aquatic birds. A documented real-world example occurred on 28 January 2017, when two cargo ships collided off the Ennore coast in Chennai, spilling oil that wave action and the southern current spread over roughly 34 km of coastline; beach sand was also fouled by oil sludge, and it took more than a thousand volunteers to clean it up. Second, humans and other organisms can contract diseases such as hepatitis and typhoid by consuming water or food contaminated by pollution; excess fluoride in drinking water specifically causes fluorosis, and in many poorer nations, waterborne disease outbreaks and epidemics result directly from contaminated water combined with poor or absent water-treatment infrastructure. …