Aerobic bacteria feed on decomposing organic matter; breaking down and combining the matter with oxygen (oxidization). The amount of oxygen used by microorganisms in the aerobic oxidation of organic matter is a measure of the Biochemical Oxygen Demand (BOD). Nutrients contribute to high BOD in water systems by stimulating plant growth. When the plants die, aerobic bacteria utilize oxygen in breaking down the decaying organic matter which leads to an increase in BOD.
Sources of Organic Matter
Changes in Aquatic Life
In water systems with high BOD most of the available oxygen is consumed by aerobic bacteria; thus, decreasing the amount of oxygen available for survival by other aquatic organisms. Eventually, as organic pollution increases, pollutant tolerant species tend to replace more sensitive species and overall species diversity is often reduced.
