Answer:
Oxygen Depletion
Explanation:
In addition to the eutrophication of water bodies, wastewater effluents also contribute to another process of deoxygenation. The biological (bacterial) breakdown of organic solids in the effluent also consumes dissolved oxygen – the biological oxygen demand (BOD). In addition, the degradation of chemicals in the effluent removes oxygen from the water through chemical reactions – the chemical oxygen demand (COD).
As was previously mentioned, the loss of dissolved oxygen in the water can result in serious immediate, short-term, or long-term consequences to aquatic life. Fish survival is particularly affected by low oxygen levels. Decreased disease resistance, reduced growth, altered swimming behaviour, feeding, migration, and reproduction, increased threat of predation, and even rapid death are some of the effects of low dissolved oxygen concentrations.
Low oxygen levels can also alter the kinds of species present in the ecosystem. With a change in food supply, some populations of species decrease, while others increase. Fish such as whitefish, walleye, and pike may disappear, while bottom-feeding fish such as carp may increase in number.
