Rainbow (Salmo gairdneri) and steelhead (Salmogairdneri) trout and fathead minnows (Pimephales promelas) were exposed to silver for 96 h in replicated flow‐through tests. Rainbow trout, fathead minnows and Daphnia magna were exposed to silver in replicated static acute tests. Steelhead trout embryo‐larval stages were tested in a flow‐through system for 60 d, and D. magna were exposed through complete life cycles in replicated static‐renewal tests. All silver concentrations were measured values. No differences were seen between flow‐through and static LC50 values. Rainbow trout 96‐h flow‐through LC50 values were 8.6 and 9.7 μg/L silver; static values were 10.9 and 8.5 μg/L. The 96‐h LC50 for steelhead trout in the flow‐through test was 9.2 μg/L. Fathead minnow 96‐h flow‐through LC50 values were 5.6 and 7.4 μg/L silver; static values were 9.4 and 9.7 μg/L. The absence of food in static tests with D. magna caused silver to be about 10 times more toxic; the 48‐h static mean EC50 value for D. magna without food was 0.9 μg/L, compared to 12.5 μg/L in the test with food. The early‐life‐stage test with steelhead trout, from newly fertilized eggs to post‐swimup juveniles, showed complete mortality at 1.3 μg/L and significant reduction in fish survival at 0.5 μg/L silver. Mean weight and length at end of test were greatly reduced at 1.1 μg/L, and were significantly different from controls at 0.1 μg/L. The mean 21‐d EC50 value for the D. magna test with food was 3.5 μg/L. The 21‐d lowest significant (α = 0.05) effect on survival occurred at 4.1 μg/L. The mean silver concentration at which there was a significant decrease in total Daphnia young/female/day after 21 d, compared to the control was 10.5 μg/L silver.

Methods are presented for using Daphnia magna, Hyalella azteca, Gammarus lacustris, Chironomus tentans and Hexagenia limbata to screen freshwater sediments for acute and chronic toxicity, bioaccumulation potential and insitu toxicity. The 48-h Daphnia tests are recommended as inexpensive, uncomplicated and sensitive acute methods. Hyalella and Chironomus are the recommended benthic test organisms, as they are easy to rear and test, they remain in intimate contact with the sediment and they exhibit high control survival. Verification studies (published elsewhere) evaluating the recommended methods and organisms are briefly summarized.

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Natural freshwater sediments from two Oregon sites were spiked with copper in the laboratory and two static toxicity tests were conducted with series of copper concentrations ranging from 59 to 10,600 mg/kg of dry sediment. Water (800 ml) was added to 1‐liter test beakers over the sediment (200 ml) and repeatedly removed and replaced to lower the aqueous copper concentrations. When copper concentrations stabilized, i.e., attained equilibrium between water and sediment, the midge Chironomus tentans, the cladoceran Daphnia magna and the amphipods Hyalella azteca and Gammarus lacustris were introduced as test animals in solid‐phase sediment toxicity bioassays. Based on dry‐weight sediment copper concentrations, LC50 values (48‐h for Daphnia, 10‐d for other organisms) ranged from 681 to 2,296 mg/kg.