In order to overcome limitations associated with the Daphnia assay, we have explored two alternative assays, the 22-h chronic Microtox ® test and the 3-day S. capricornutum test, as substitutes. During this study, we compared the two assays using both a simple TDS standard solution and field water samples from two Alaskan mines. Using EC 20 values, our results suggest that simple TDS standard solutions are not representative of environmental water samples of equivalent TDS concentrations. When comparing assays, our results showed that the 22-h Microtox ® assay was more reproducible and sensitive to effluent waters than the algal assay. Principle component analysis indicated that the 22-h Microtox ® test was generally more sensitive to nickel, ammonia and chloride while the S. capricornutum growth test appeared sensitive to cadmium levels.