Comparison of the partitioning of pesticides relative to the survival and behaviour of exposed amphipods
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Pesticides sprayed on farmlands can end up in rivers and be transported into estuaries, where they could affect aquatic organisms in freshwater and marine habitats. A series of experiments were conducted using the amphipod Corophium volutator Pallas (Amphipoda, Corophiidae) and single pesticides, namely atrazine (AT), azinphos-methyl (AZ), carbofuran (CA) and endosulfan (EN) that were added to sediments and covered with seawater. Our goal was to compare the concentrations affecting the survival of the animals relative to potential attractant or repellent properties of sediment-spiked pesticides. The avoidance/preference of contaminated/reference sediments by amphipods was examined after 48 and 96 h of exposure using sediments with different organic carbon content. The octanol–water partition coefficients (log Kow) ranked the pesticides binding to sediments as EN > AZ > AT > CA. LC50 and LC20 covered a wide range of nominal concentrations and ranked toxicity as CA-AZ > EN > AT. Under the experimental set up, only EN initiated an avoidance response and the organic carbon normalised concentration provided consistent results. Using the present data with wide confidence limits, >20% of a population of C. volutator could perish due to the presence of EN before relocation or detecting CA or AZ in sediments by chemical analysis.
KeywordsAmphipods Corophium volutator Behaviour Survival Pesticides
We would like to thank our collaborators in this first year of the study, Mr. Lea Murphy, Deryck Mills, Delly Keen, John McKinnon, and Danny Geldert at DFO, PEI who facilitated our sampling in the Wilmot and Dunk Rivers, by providing a boat, GPS system, sampling experience and enthusiasm. We also wish to acknowledge funding from Health Canada through the Department of Fisheries and Oceans under the National Pesticide Research Fund.
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