Great Basin Naturalist


Acute, short-term (96-hour) tests were conducted to determine the relative sensitivity of low oxygen concentrations to 20 species of aquatic insects. In addition, the longer-term effects of low oxygen levels on the survival, molting, growth, and emergence of 21 species were studied. This paper encompasses work conducted at the University of Montana Biological Station from 1968 to 1970 and at the University of Utah from 1966 to 1972.

An evaluation of the average minimum dissolved-oxygen requirements of the different groups of aquatic insects tested indicates that the mayflies are the most sensitive, that the stoneflies are next, and that the caddis flies, freshwater shrimp, true flies, and damselflies follow, in that order. While two species of mayfly could tolerate as low a dissolved-oxygen concentration as 3.3 mg/L for 10 days, a level of 4.6 mg/L was required for 50-percent survival at 30 days. Fifty percent of the true flies and damselflies tested were able to survive at levels ranging from 2.2 to 2.8 mg/L for periods ranging from 20 to 92 days.