How much dissolved oxygen do organisms need?
It depends on what kind of organism it is. Generally, aquatic organisms can be divided into two types, cold water and warm water organisms. Cold water organisms: These would include fish, such as salmon and trout, and aquatic insects, such as stoneflies and mayfly nymphs. Generally, these species require a minimum DO (dissolved oxygen) level of at least 6.0 mg/L. Additionally, these cold water organisms require special conditions when spawning (laying eggs). Eggs laid by salmon and trout are especially delicate, and the fry (baby fish) that hatch are sensitive as well. For these fish to successfully reproduce, a DO level above 7.0 mg/L is required. Warm water organisms: These would include fish, such as bass, carp, and catfish, and aquatic insects, such as blackflies and midge larvae. Generally, these species require less dissolved oxygen than cold water organisms. If the DO level drops below 4.0-5.0 mg/L, the organisms will become stressed. In an environment with a low level of dissol
