What is dissolved oxygen and why is it important?
Dissolved oxygen is required by all aquatic animals. Low dissolved oxygen levels (hypoxia) can impair animal growth or reproduction, and the complete lack of oxygen (anoxia) will kill animals. Animals with limited mobility such as oysters and clams are particularly vulnerable to hypoxic or anoxic conditions. Even fast swimmers such as fish can become trapped in areas with low oxygen or no oxygen. Dissolved oxygen levels are affected by a number of factors, including: Water temperature How well mixed the water is (for example, the presence or absence of a pycnocline) How much oxygen is being produced by biological processes (such as photosynthesis by plants), and How much oxygen is being used up by abiotic and biological processes (for example, respiration or the decomposition of organic matter such as dead phytoplankton) in the water column or in the sediments and, at the sediment-water interface. The pycnocline is the place in the water column where there is an abrupt change in densit
