Define BOD. What is its significance in an aquatic ecosystem?

Explanation

Biochemical oxygen demand (BOD) refers to the amount of dissolved oxygen needed by aerobic biological organisms required to break down organic material present in a given water sample at certain temperature over a specific period of time. It is commonly expressed in milligrams of oxygen consumed per litre of sample during 5 days of incubation at `20^@C` and is often used as a "surrogate of the degree of organic pollution of water". BOD is an important water quality parameter because it provides an index to assess the effect of discharged wastewater on the environment. The higher the BOD value, the greater the amount of organic matter or "food” available for oxygen consuming bacteria.