Modeling combined effects of pulsed exposure to carbaryl and chlorpyrifos on Gammarus pulex.

Aquatic risk assessment can be improved if we are able to quantitatively predict the effects resulting from sequential pulsed exposure to multiple compounds. We evaluate two modeling approaches, both extended to suit multiple compounds, the semi-mechanistic threshold damage model (TDM), and a model based on time-weighted averages (TWA). The TDM predicts that recovery of damage to Gammarus pulex from exposure to chlorpyrifos takes longer than that from exposure to carbaryl and consequently that the sequence of exposure matters. We measured survival of the freshwater invertebrate Gammarus pulex after sequential pulsed exposure to carbaryl and chlorpyrifos. Two groups of organisms were exposed to a first pulse of either carbaryl or chlorpyrifos for 1 day and then, after a recovery period of two weeks, to a second pulse with the other compound. The comparison of mortalities caused by each pulse, as well as combined mortalities in both treatments, show that the sequence of exposure to pulses of contaminants does indeed matter. Previous exposure to chlorpyrifos leads to significantly increased mortality from subsequent pulses of carbaryl, but not the other way round. The TDM facilitates a process-based ecotoxicological explanation by simulating the recovery dynamics and outperforms the TWA model.

[1]  Development of a multi-component Damage Assessment Model (MDAM) for time-dependent mixture toxicity with toxicokinetic interactions. , 2006, Environmental science & technology.

[2]  Hong-xia Yu,et al.  Evaluation of sensitivity and specificity of two crustacean biochemical biomarkers , 2000 .

[3]  R. Handy.  Intermittent exposure to aquatic pollutants : assessment, toxicity and sublethal responses in fish and invertebrates , 1994 .

[4]  J. Giddings,et al.  Effects analysis of time‐varying or repeated exposures in aquatic ecological risk assessment of agrochemicals , 2002, Environmental toxicology and chemistry.

[5]  Paul J. Van den Brink,et al.  Effects of the insecticide dursban® 4E (active ingredient chlorpyrifos) in outdoor experimental ditches: I. Comparison of short‐term toxicity between the laboratory and the field , 1996 .

[6]  K. Kuhn,et al.  Detecting sublethal effects of organophosphates by measuring acetylcholinesterase activity in Gammarus , 1994, Bulletin of environmental contamination and toxicology.

[7]  Roman Ashauer,et al.  Uptake and Elimination of Chlorpyrifos and Pentachlorophenol into the Freshwater Amphipod Gammarus pulex , 2006, Archives of environmental contamination and toxicology.

[8]  J. Stark,et al.  Acute toxicity of drainage ditch water from a Washington State cranberry-growing region to Daphnia pulex in laboratory bioassays. , 2002, Ecotoxicology and environmental safety.

[9]  Lorraine Maltby,et al.  Evaluation of the Gammarus pulex in situ feeding assay as a biomonitor of water quality: Robustness, responsiveness, and relevance , 2002, Environmental toxicology and chemistry.

[10]  G. Koelle.  4 – Pharmacology and toxicology of organophosphates , 1992 .

[11]  Roman Ashauer,et al.  New ecotoxicological model to simulate survival of aquatic invertebrates after exposure to fluctuating and sequential pulses of pesticides. , 2007, Environmental science & technology.

[12]  J. Kreuger.  Pesticides in stream water within an agricultural catchment in southern Sweden, 1990-1996. , 1998, The Science of the total environment.

[13]  A. Murty,et al.  27 – Toxicity of anticholinesterases to aquatic organisms , 1992 .

[14]  P. Capel,et al.  Comparison of pesticides in eight U.S. urban streams , 2000 .

[15]  L. Maltby,et al.  The lethal and sublethal responses of gammarus pulex to stress: Sensitivity and sources of variation in an in situ bioassay , 1991 .

[16]  J. Hermens,et al.  Analysis of the Time-Dependent Acute Aquatic Toxicity of Organophosphorus Pesticides: The Critical Target Occupation Model , 1999 .

[17]  R. Schulz,et al.  Assessment of insecticide contamination in runoff and stream water of small agricultural streams in the main soybean area of Argentina. , 2005, Chemosphere.

[18]  Colin R. Janssen,et al.  Comparison of the Effect of Different pH Buffering Techniques on the Toxicity of Copper and Zinc to Daphnia Magna and Pseudokirchneriella Subcapitata , 2004, Ecotoxicology.

[19]  J BrinkvandenP.,et al.  Effects of chronic low concentrations of pesticides chlorpyrifos and atrazine in indoor freshwater micro-cosms , 1995 .

[20]  Roman Ashauer,et al.  Simulating toxicity of carbaryl to Gammarus pulex after sequential pulsed exposure. , 2007, Environmental science & technology.

[21]  Roman Ashauer,et al.  Predicting effects on aquatic organisms from fluctuating or pulsed exposure to pesticides , 2006, Environmental toxicology and chemistry.