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(P306) Test system for delivery of consistent levels of ammonia in sediment pore water during toxicity tests with unionid mussels.
Allran, John*,1,2, Newton, Teresa1, O'Donnell, Jon1, Bartsch, Michelle1, Richardson, William1, 1 U.S. Geological Survey, Upper Midwest Environmental Sciences Center, La Crosse, WI, United States2 Dynamac Corporation, Durham, NC, United States
ABSTRACT- Existing sediment exposure systems are not suitable for ammonia toxicity studies with juvenile unionids because ammonia readily diffuses from the sediment into overlying water. Juveniles are sensitive to contaminants because they reside in sediments; however, their small size makes recovery from test sediments difficult. We modified an existing system to provide continual infusion of test sediments with ammonia and allow recovery of juveniles. We conducted a 10-d experiment using two concentrations of NH4Cl (5.7 and 57.4 mg total ammonia nitrogen, TAN/L) that bracket the range for which acute toxicity has been observed in juveniles. The test system was successful in (1) maintaining consistent concentrations of TAN in sediment pore water over 10 d, (2) delivering measured concentrations of TAN in pore water that averaged > 83% of nominal concentrations, (3) maintaining adequate water quality, and (4) providing juveniles contact with sediment particles as an important food source and source of contaminants. The system was relatively inexpensive to construct, and it was easy to calibrate, run, and maintain. This system may provide researchers another tool to evaluate the effects of volatile sediment-associated contaminants to a benthic macroinvertebrates.
Key words: freshwater mussels, ammonia, test design, sediment
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