What does a high Biochemical Oxygen Demand (BOD) indicate about a water body?

A high Biochemical Oxygen Demand (BOD) indicates the presence of substantial organic matter in a water body that is undergoing decomposition. BOD measures the amount of dissolved oxygen that microorganisms require to break down organic material over a specific time period, usually five days. When BOD levels are elevated, it signifies that there is a significant quantity of biodegradable materials present, such as decaying plant and animal matter or organic pollutants. This high demand for oxygen can lead to oxygen depletion in the water, adversely affecting aquatic life. In essence, a high BOD reflects a polluted environment where there is a lot of biological activity aimed at decomposing that organic matter.