Effects of toxicants on community metabolism in pools

Estimates of community metabolism of simulated natural environments were dcrivcd by diel oxygen techniques over a period of nine months. During this time, toxicants were added to some of the pools. "Natural" environmental factors and toxicants that did not affect the communities (0.02 mg/liter p,p' DDT; 0.1 mg/liter antimycin A; and 9.2 mg/liter KMnO,I) usually resulted in simultaneous changes, up or down, in both community photosynthesis and respiration. Concentrations (mg/liter) of 0.9 and 2.6 formalin, 10.0 nigrosine black, 10.0 and 2.0 malachite green, 0.1 Diquat, and 0,.5 and 5.0 CUSO.~ usually tlcprcsscd community oxygen production and increased community respiration for periods of 1 to 20 weeks.