Relative sensitivity of an amphipod Hyalella azteca, a midge Chironomus dilutus, and a unionid mussel Lampsilis siliquoidea to a toxic sediment

Chris G. Ingersoll, James L. Kunz, Jamie P. Hughes, Ning Wang, D. Scott Ireland, David R. Mount, J. Russell Hockett, Theodore W. Valenti

The objective of the present study was to evaluate the relative sensitivity of test organisms in exposures to dilutions of a highly toxic sediment contaminated with metals and organic compounds. One dilution series was prepared using control sand (low total organic carbon [<0.1% TOC, low binding capacity for contaminants]) and a second dilution series was prepared using control sediment from West Bearskin (WB) Lake, MN (high TOC [about 10% TOC, higher binding capacity for contaminants]). Test organisms included an amphipod (Hyalella azteca; 10-d and 28-d exposures), a midge (Chironomus dilutus; 20-d and 48-d exposures started with <1-h-old larvae or 13-d and 48-d exposures started with 7-d-old larvae), and a unionid mussel (Lampsilis siliquoidea; 28-d exposures). Relative species sensitivity depended on the toxicity endpoint and the diluent. All 3 species were more sensitive in sand dilutions than in WB sediment dilutions. The <1-h-old C. dilutus were more sensitive than 7-d-old C. dilutus, but replicate variability was high in exposures started with the younger midge larvae. Larval biomass and adult emergence endpoints of C. dilutus exhibited a similar sensitivity. Survival, weight, and biomass of H. azteca were more sensitive endpoints in 28-d exposures than in 10-d exposures. Weight and biomass of L. siliquoidea were sensitive endpoints in both sand and WB sediment dilutions. Metals, ammonia, oil and other organic contaminants may have contributed to the observed toxicity. This article is protected by copyright. All rights reserved.