Effects of ammonia and chlorine on fish in streams receiving secondary discharges

Although ammonia and residual chlorine toxicity have been individually studied in the laboratory for many years, their relative impacts on the total lotic environment have not been clearly demonstrated under field conditions. Because these materials are discharged concomitantly, it is difficult to isolate and measure their individual impacts. This paper reports on a study to define and separate the relative effects of the two pollutants upon fishes. Study materials, methods and results are discussed. In the major study finding, residual chlorine in wastewater effluents was identified as the main toxicant suppressing the diversity, size, and quantity of fish in two Illinois streams.