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Comparative sensitivity of five species of macrophytes and six species of algae to atrazine, metribuzin, alachlor, and metolachlor

Authors

  • James F. Fairchild,

    Corresponding author
    1. Environmental and Contaminants Research Center, U.S. Geological Survey, 4200 New Haven Road, Columbia, Missouri 65201
    • Environmental and Contaminants Research Center, U.S. Geological Survey, 4200 New Haven Road, Columbia, Missouri 65201
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  • D. Shane Ruessler,

    1. Florida Caribbean Science Center, US. Geological Survey 7920 NW. 71st Street Gainesville, Florida 32653
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  • A. Ron Carlson

    1. National Health and Environmental Effects Research Laboratory–Midcontinent Ecology Division, U.S. Environmental Protection Agency, 6201 Congdon Boulevard, Duluth, Minnesota 55804
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Abstract

This study determined the relative sensitivity of five species of aquatic macrophytes and six species of algae to four commonly used herbicides (atrazine, metribuzin, alachlor, and metolachlor). Toxicity tests consisted of 96-h (duckweed and algae) or 14-d (submerged macrophytes) static exposures. The triazine herbicides (atrazine and metribuzin) were significantly more toxic to aquatic plants than were the acetanilide herbicides (alachlor and metolachlor). Toxicity studies ranked metribuzin > atrazine > alachlor > metolachlor in decreasing order of overall toxicity to aquatic plants. Relative sensitivities of macrophytes to these herbicides decreased in the order of Ceratophyllum > Najas > Elodea > Lemna > Myriophyllum. Relative sensitivities of algae to herbicides decreased in the order of Selenastrum > Chlorella > Chlamydomonas > Microcystis > Scenedesmus > Anabaena. Algae and macrophytes were of similar overall sensitivities to herbicides. Data indicated that Selenastrum, a commonly tested green alga, was generally more sensitive compared to other plant species. Lemna minor, a commonly tested floating vascular plant, was of intermediate sensitivity, and was fivefold less sensitive than Ceratophyllum, which was the most sensitive species tested. The results indicated that no species was consistently most sensitive, and that a suite of aquatic plant test species may be needed to perform accurate risk assessments of herbicides.

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