Why is dissolved oxygen important?
Dissolved oxygen (DO) is important because most aquatic creatures – those that live in the water – breathe by obtaining oxygen that is dissolved in the water. If there is not enough oxygen in the water, the creatures have to breathe more frequently to obtain sufficient oxygen, stressing their systems. Insufficient DO basically suffocates fish and other aquatic creatures. Low dissolved oxygen can also result in chemical changes that affect water quality. For example, anaerobic (without oxygen) conditions result in the release of phosphorus from sediments. This phosphorus acts as a fertilizer, and can result in algal blooms. Low dissolved oxygen may also be a factor in the conversion of mercury to the toxic form, methyl mercury.
