Multiple sublethal chemicals negatively affect tadpoles of the green frog, Rana clamitans

Authors

  • Michelle D. Boone,

    Corresponding author
    1. U.S. Geological Survey Columbia Environmental Research Center, 4200 New Haven Road, Columbia, Missouri 65201
    2. Division of Biological Sciences, 105 Tucker Hall, University of Missouri, Columbia, Missouri 65211, USA
    Current affiliation:
    1. M.D. Boone is Miami University, Department of Zoology, 212 Pearson Hall, Oxford, OH 45056, USA
    • U.S. Geological Survey Columbia Environmental Research Center, 4200 New Haven Road, Columbia, Missouri 65201
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  • Christine M. Bridges,

    1. U.S. Geological Survey Columbia Environmental Research Center, 4200 New Haven Road, Columbia, Missouri 65201
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  • James F. Fairchild,

    1. U.S. Geological Survey Columbia Environmental Research Center, 4200 New Haven Road, Columbia, Missouri 65201
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  • Edward E. Little

    1. U.S. Geological Survey Columbia Environmental Research Center, 4200 New Haven Road, Columbia, Missouri 65201
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Abstract

Many habitats may be exposed to multiple chemical contaminants, particularly in agricultural areas where fertilizer and pesticide use are common; however, the singular and interactive effects of contaminants are not well understood. The objective of our study was to examine how realistic, sublethal environmental levels of ammonium nitrate fertilizer (0, 10, 20 mg/L and ammonium chloride control) and the common insecticide carbaryl (0 or 2.5 mg/L) individually and interactively affect the development, size, and survival of green frog (Rana clamitans) tadpoles. We reared tadpoles for 95 d in outdoor 1,000-L polyethylene ponds. We found that the combination of carbaryl and nitrate had a negative effect on development and mass of tadpoles compared to the positive effect that either contaminant had alone. Presence of carbaryl was generally associated with short-term increases in algal resources, including ponds exposed to both carbaryl and nitrate. However, with exposure to nitrate and carbaryl, tadpole mass and development were not positively affected as with one chemical stressor alone. The combination of these sublethal contaminants may reduce the ability of amphibians to benefit from food-rich environments or have metabolic costs. Our study demonstrates the importance of considering multiple stressors when evaluating population-level responses.

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