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Effect of sediment-associated pyrethroids, fipronil, and metabolites on Chironomus tentans growth rate, body mass, condition index, immobilization, and survival

Authors

  • Jonathan D. Maul,

    1. Fisheries and Illinois Aquaculture Center and Department of Zoology, Southern Illinois University, 1125 Lincoln Drive, Carbondale, Illinois 62901, USA
    2. The Institute of Environmental and Human Health and Department of Environmental Toxicology, Texas Tech University, 1207 Gilbert Drive, Lubbock, Texas 79409, USA
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  • Amanda A. Brennan,

    1. Fisheries and Illinois Aquaculture Center and Department of Zoology, Southern Illinois University, 1125 Lincoln Drive, Carbondale, Illinois 62901, USA
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  • Amanda D. Harwood,

    1. Fisheries and Illinois Aquaculture Center and Department of Zoology, Southern Illinois University, 1125 Lincoln Drive, Carbondale, Illinois 62901, USA
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  • Michael J. Lydy

    Corresponding author
    1. Fisheries and Illinois Aquaculture Center and Department of Zoology, Southern Illinois University, 1125 Lincoln Drive, Carbondale, Illinois 62901, USA
    • Fisheries and Illinois Aquaculture Center and Department of Zoology, Southern Illinois University, 1125 Lincoln Drive, Carbondale, Illinois 62901, USA
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Abstract

Pyrethroids and fipronil insecticides partition to sediment and organic matter in aquatic systems and may pose a risk to organisms that use these matrices. It has been suggested that bioavailability of sediment-sorbed pesticides is reduced, but data on toxicity of sediment-associated pesticides for pyrethroids and fipronil are limited. In the current study, 10-d sediment exposures were conducted with larval Chironomus tentans for bifenthrin, lambda-cyhalothrin, permethrin, fipronil, fipronil-sulfide, and fipronilsulfone, the last two being common fipronil metabolites. Sublethal endpoints included immobilization, instantaneous growth rate (IGR), body condition index, and growth estimated by ash-free dry mass (AFDM). Pyrethroid lethal concentrations to 50% of the population (LC50s) were 6.2, 2.8, and 24.5 μg/g of organic carbon (OC) for bifenthrin, lambda-cyhalothrin, and permethrin, respectively; with the former two lower than previously published estimates. Fipronil, fipronil-sulfide, and fipronilsulfone LC50 values were 0.13, 0.16, and 0.12 μg/g of OC, respectively. Ratios of LC50s to sublethal endpoints (immobilization, IGR, and AFDM) ranged from 0.90 to 9.03. The effects on growth observed in the present study are important because of the unique dipteran life cycle involving pupation and emergence events. Growth inhibition would likely lead to ecological impacts similar to mortality (no emergence and thus not reproductively viable) but at concentrations up to 4.3 times lower than the LC50 for some compounds. In addition, C. tentans was highly sensitive to fipronil and metabolites, suggesting that dipterans may be important for estimating risk and understanding effects of phenylpyrazole-class insecticides on benthic macroinvertebrate communities.

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