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INTRODUCTION <br /> Biomonitoring provides an effective means to test multimedia effluents for <br /> toxicity. Detection of such effects solely through chemical analyses are often <br /> difficult to accomplish. <br /> The Colorado Water Quality Control Division requires certain dischargers <br /> holding NPDES permits to perform both acute and chronic biomonitoring tests as <br /> part of their permit requirements. The chronic tests measure significant differences <br /> in either reproduction (Ceriodaphnia) or growth (fathead minnows) between control <br /> and exposed organisms. These tests are conducted over 7 days as opposed to the <br /> 48 hr and 96 hr acute tests which measure mortalities. <br /> The present report discusses the results of a special chronic biomonitoring <br /> test conducted on the effluent from Sunnyside's AT-004 mine effluent. This effluent <br /> was used as the dilution water for a test conducted using a series of Sodium <br /> Bromide (NaBr) concentrations. This test was conducted during September 1994. <br /> MATERIALS AND METHODS <br /> Sample Collection <br /> Grab samples of the plant discharge were collected in one-gallon containers <br /> on September 19, 21, and 23, 1994. Immediately after collection, samples were <br /> transported to the lab where they were refrigerated at 40C until use. Chain of <br /> custody forms showing sample transfer are included in Appendix 1. <br /> Dilution Water <br /> The effluent itself was used as the dilution water source in the test. To this <br /> was added varying amounts of Sodium Bromide to produce the bromide <br /> concentrations for the test. A control consisting of the laboratory reconstituted <br /> freshwater was run with the test as a quality check on the health of the test <br /> organisms. This water was prepared by mixing stock solutions of potassium <br /> chloride, sodium bicarbonate, and magnesium sulfate, and calcium sulfate powder <br /> with deionized water. <br /> Test Organisms <br /> The tests were conducted with Ceriodaphnia sp. and fathead minnows <br /> (Pimephales promelas). The Ceriodaphnia were cultured in Seac rest's laboratory. <br /> Stock cultures are grown in 3 1 glass beakers and/or aquaria. Brood females are <br /> cultured in individual plastic cups for a period of 14 days. Neonates born daily are <br /> removed from the brood chambers and used in tests. Brood and stock organisms <br /> are fed a mixture of digested trout chow, alfalfa, and yeast and an equal volume of <br /> algae daily. <br /> One day old fathead minnows cultured in the laboratory were used in the <br /> tests. The fish were obtained from eggs produced by adults in 10 gallon aquaria. <br /> Eggs were removed from the aquaria after fertilization and aerated until hatching. <br /> Normally, eggs hatch in 4-5 days. Fish were fed newly hatched brine shrimp daily. <br />