Methods for Measuring the Toxicity and Bioaccumulation of Sediment-associated Contaminants with Freshwater Invertebrates - Second Edition

Procedures are described for testing freshwater organisms in the laboratory to evaluate the potential toxicity or bioaccumulation of chemicals in whole sediments. Sediments may be collected from the field or spiked with compounds in the laboratory. Toxicity methods are outlined for two organisms, the amphipod Hyalella azteca and the midge Chironomus tentans. Toxicity tests with amphipods or midges are conducted for 10 d in 300-mL chambers containing 100 mL of sediment and 175 mL of overlying water. Overlying water is renewed daily and test organisms are fed during the toxicity tests. The endpoints in the 10-d toxicity test with H. azteca and C. tentans are survival and growth. Procedures are primarily described for testing freshwater sediments; however, estuarine sediments (up to 15‰ salinity) can also be tested in 10-d sediment toxicity tests with H. azteca. Guidance is also provided for conducting long-term sediment toxicity tests with H. azteca and C. tentans. The long-term sediment exposures with H. azteca are started with 7- to 8-d-old amphipods. On Day 28 of the sediment exposure, amphipods are isolated from the sediment and placed in water-only chambers where reproduction is measured on Day 35 and 42. Endpoints measured in the amphipod test include survival (Day 28, 35, and 42), growth (on Day 28 and 42), and reproduction (number of young/female produced from Day 28 to 42). The long-term sediment exposures with C. tentans start with newly hatched larvae (<24-h old) and continue through emergence, reproduction, and hatching of the F1 generation (about 60-d sediment exposures). Survival and growth are determined at 20 d. Starting on Day 23 to the end of the test, emergence and reproduction of C. tentans are monitored daily. The number of eggs/ female is determined for each egg mass, which is incubated for 6 d to determine hatching success. The procedures described in Sections 14 and 15 include measurement of a variety of lethal and sublethal endpoints with Hyalella azteca and Chironomus tentans; minor modifications of the basic methods can be used in cases where only a subset of these endpoints is of interest. Guidance for conducting 28-d bioaccumulation tests with the oligochaete Lumbriculus variegatus is also provided in the manual. Overlying water is renewed daily and test organisms are not fed during bioaccumulation tests. Methods are also described for determining bioaccumulation kinetics of different classes of compounds during 28-d exposures with L. variegatus.