Effect of Low Oxygen Concentration on Survival and Emergence of Aquatic Insects

Safe concentrations of dissolved oxygen for survival and adult emergence of larvae of nine species of aquatic insects, including mayflies, stoneflies, caddisflies, and midges, ranged from 0.6 mg/liter for the midge Tanytarsus dissimilis to slightly less than saturation for the emergence of Ephemera simulans (18.5 C). All species tested were less tolerant of low oxygen concentrations for 30 days than for 96 hours (90% of E. simulans survived 4 mg/liter for 96 hours, but no adults emerged successfully). Long-term studies are essential for the accurate assessment of oxygen stress in aquatic insects.