With respect to Water Pollution, Cause, Effects and Mitigation measures of Oxygen

Causes:
Although oxygen concentrations fluctuate under natural conditions, severe oxygen depletion usually results from human activities. Introducing large quantities of biodegradable organic materials, plant, fish, or animal matter, into surface waters can rapidly consume available oxygen. Leaves, lawn clippings, sewage, manure, milk solids, and other food processing wastes are examples of oxygen-depleting organic materials that enter our surface waters. Oxygen depletion can also result from chemical reactions that do not involve bacteria. Other factors, such as temperature and salinity (saltiness), influence the amount of oxygen dissolved in water.
Effects:
Such depletion of Oxygen from water sources is harmful for all including human, aquatic as well as terrestrial animals. Aquatic animals breathe using oxygen of water. It may cause the death of aquatic life and cause severe health hazards to human beings.
Mitigation Measures:
Efforts should be made for managing waste disposal