|Shields Jr, Fletcher|
Submitted to: Bulletin of Environmental Contamination and Toxicology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/21/2009
Publication Date: N/A
Interpretive Summary: Bottom sediments from small Mississippi Delta oxbow lakes were tested to determine if they were toxic to small aquatic test organisms called “scuds.” Scuds are crustaceans like shrimp and crayfish that are sensitive to low concentrations of contaminants such as pesticides. Some of the sediments were found to be toxic and this toxicity was attributed to a group of historically used pesticides similar to DDT that are no longer used but that remain in the sediments for a long time. This research shows that the long lived pesticides that were used in the past still remain in some places in the environments and still exhibit some level of toxicity. This research further demonstrates that these organisms provide an inexpensive screening tool that can be used to test toxicity of sediments before expensive restoration projects are undertaken. This information should be useful to both scientists and federal and state resource managers.
Technical Abstract: As part of an environmental quality assessment, sediment from four sites in three Coldwater River, Mississippi backwaters was examined using 28 d Hyalella azteca bioassays and chemical analyses for 33 pesticides, 7 metals and 7 PCBs. Mortality occurred in the DeSoto County backwater while growth impairment occurred in two of three sites in Tunica County backwaters. Precopulatory guarding behavior was not as sensitive as growth. Fourteen contaminants (7 metals, 7 pesticides) were detected in sediments. Survival was associated with heptachlor while growth and behavior were associated with organochlorine pesticides including aldrin, 'BHC, 'BHC, heptachlor. Effects on survival, growth and precopulatory guarding behavior were associated with several sediment contaminants. Spearman Rank correlations showed significant associations with the organochlorine insecticide heptachlor and H. azteca survival. In addition, organochlorine insecticides aldrin, 'BHC, 'BHC (lindane) and heptachlor had significant relationships with growth and precopulatory guarding behavior. Based upon weight of evidence from reported PECs and associations with observed H. azteca responses, most likely source of observed sediment toxicity was due to organochlorine pesticides heptachlor, lindane, and aldrin.