Effects of Turbidity on Ventilation Rates and Oxygen Consumption of Green Sunfish, Lepomis cyanellus

Abstract

Ventilation and oxygen consumption rates of green sunfish exposed to bentonite clay suspensions were measured at 5, 15, 25, and 35 C. Ventilation rates were not affected by bentonite clay suspensions below 2,125 FTU (Formazin Turbidity Units) at 5 C, 1,012 FTU at 15 C, and 898 FTU at 25 C. At turbidity levels exceeding 1,012 FTU at 15 C and 898 FTU at 25 C ventilation rates increased 50-70%. Tests were inconclusive at 35 C due to high mortality. Oxygen consumption rates were not affected by turbid suspensions of up to 3,500 FTU at any of the four temperatures. Evidence suggests that increased ventilation rates under highly turbid conditions are a means of compensating for reduced respiratory efficiency and a strategy for maintaining a constant oxygen uptake. The costs of increased ventilation rates were probably met by a reduction in activity.