Submitted to: Bulletin of Environmental Contamination and Toxicology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: January 8, 2007
Publication Date: March 20, 2007
Citation: Smith Jr, S., Lizotte Jr, R.E., Knight, S.S. 2007. Pesticide body residues of Hyalella azteca exposed to Mississippi Delta sediments. Bulletin of Environmental Contamination and Toxicology. 78(1):26-29. DOI:10.1007/s00128-007-9020-2. Interpretive Summary: Watershed sediments, acting as sinks, can accumulate pesticides and expose sediment-dwelling (benthic), epibenthic and even aquatic organisms to concentrations decreasing survival, growth, or reproduction should sediments become re-suspended in the water column. The current study examines the accumulation of pesticides in the test organism Hyalella azteca, exposed for 28 days to sediments from nine watersheds in the Mississippi Delta: three reference watersheds (NWR), three with active best management practices (BMPs) and three listed by the USEPA (303d) for legacy (past-use) pesticide concentrations. We found that Mississippi Delta sediments contained legacy compounds, as well as current-use insecticides and herbicides, in sufficient enough concentrations to move from sediment to H. azteca tissues within 28 days, eliciting biologically relevant growth impairment. This is important because lake and bayou sediments can accumulate pesticides in concentrations that might affect survival, growth, and reproduction of other benthic, epibenthic, and even aquatic animals. Further studies are planned to better understand the role of H. azteca pesticide body residues within the aquatic environment.
Technical Abstract: Surface sediment samples (top 5 cm) were collected during summer (June to July) 2004 at three sites within each of nine watersheds located in the Mississippi Delta, divided into three categories: NWR (reference), BMP (Best Management Practice), and 303d (impaired). Twenty-eight day static non-renewal whole sediment exposures using Hyalella azteca were performed using standard protocols. At the conclusion of the 28 d exposure period, surviving animals were counted, weighed (as wet weight) and analyzed for body burden pesticides. Chemical analysis revealed variation in animal pesticide body residue concentrations for 11 of 17 pesticides examined among the three watershed categories. The herbicides, trifluralin and pendimethalin, had no measurable body residue amounts in animals exposed to sediments from any watershed, whereas, the concentrations of the herbicides, cyanazine, alachlor and metolachlor, were greatest in animals exposed to BMP category sediments. Atrazine (herbicide) occurred in the greatest concentrations of any pesticide examined but was not significantly different among watershed categories. H. azteca exposed to BMP category sediments had the greatest herbicide body residues. Intermediate herbicide body residues were observed in animals exposed to 303d watersheds. Lowest herbicide body residues occurred in organisms exposed to NWR watersheds. The insecticides, chlorpyrifos, methyl parathion, chlorfenapyr, and l-cyhalothrin, were greatest in animals exposed to BMP sediments. Greatest total insecticide body residues occurred in animals from BMP lake sediments and were lowest in Cassidy Bayou (303d) and Columbus Lake (NWR). The metabolite, fipronil sulfone was greatest in animals exposed to BMP watershed sediments and lowest in NWR. Legacy compounds (p,p’-DDT and metabolites) were greatest in H. azteca exposed to BMP and 303d sediments. Based upon Hyalella azteca pesticide body residues accumulated via contaminated Mississippi Delta sediments, significant concentrations of legacy compounds, as well as current-use insecticides and herbicides, can move from sediment to H. azteca tissues within 28 days eliciting biologically relevant growth impairment. Further studies are needed to elucidate the role of detritivore body residue pesticide contamination within aquatic ecosystems and associated effects on predatory aquatic organisms.