EPA-600/4-84-087. "November 1984." -- cover "Technical monitor, Wesley L. Kinney, Advanced Monitoring Systems Division, Environmental Monitoring Systems Laboratory, Las Vegas, Nevada" -- cover Cover title Includes bibliographical references (pages 43-44). Print reproduction. Contract Number: EPA contract 68-03-3050

"Instream toxicity tests using the larval fathead minnow Pimephales promelas and the cladoceran Ceriodaphnia reticulata were conducted on Prickly Pear Creek, Montana waters to study toxicity persistence in a stream. The toxicity source was Spring Creek, a tributary of Prickly Pear Creek. Gold mining tailing and settling ponds in the Spring Creek drainage release zinc, copper and cadmium to Prickly Pear Creek via Spring Creek. Stream survey characterization of flow regimes, water quality,and biotic conditions was accomplished in conjunction with toxicity testing. The study objectives were to : 1) develop a data base for validation of a toxicity persistence model; 2) assess the applicability of data from the Prickly Pear Creek study relative to model assumptions; and 3) assess field techniques for acquiring model input data. Toxicity to the test organisms was primarily due to zinc and copper in Spring Creek waters. Changes in Prickly Pear Creek toxicity downstream from the Spring Creek confluence were primarily due to dilution and complied with model assumptions. However, other unidentified toxicants were present in other tributary waters, and Spring Creek was not the sole source of toxicity in Prickly Pear Creek waters. C. reticulata was highly sensitive to toxicity in Spring Creek waters and provided model input data. Pimephales promelas had a higher tolerance, and bioassay data from these organisms could not be used for model input. In the field, test organism nutritional problems were encountered using procedures described in bioassay protocols for both of these organisms. The problem was eliminated in C. reticulata bioassays by using cerophyl as food. Either a quantitative food regime should be developed for P. promelas or a nonfeeding test used in the future.