Abstract
A field method for the rapid estimation of chemical and biological activities in sediments was developed. This spectrophotometric test is based on the quantitative reduction of the dye resazurin by chemically reducing substances and by dehydrogenase in microorganisms; the chemical and biological activities are differentiated by using m-cresol to inhibit the dehydrogenase. Activity is expressed as μmol resazurin reduced h -1 g -1 sediment (dry weight). Dry weights of the sediment samples are determined by membrane filtration and oven drying. Replicate samples from Hamilton Harbour and Bay of Quinte (Lake Ontario) and from Thunder Bay and Batchawana Bay (Lake Superior) were examined. Hamilton Harbour (heavy industry) had both low biological and low chemical activity; Bay of Quinte (eutrophic) had high chemical and biological activity. Samples from Thunder Bay showed high chemical and biological activity near an area receiving industrial wastes but moderate to low activity in an “unpolluted” area. Batchawana Bay (oligotrophic) had only low to moderate chemical and biological activity. The field method offers ease of performance, sensitivity, and stability of samples as well as good reproducibility. Comparison is made between results with this test and those with a respirometer.
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