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A methodology for inferring the causes of observed impairments in aquatic ecosystems

Authors

  • Glenn W. Suter II,

    Corresponding author
    1. U.S. Environmental Protection Agency, National Center for Environmental Assessment, 26 W. Martin Luther King Dr., MS 117, Cincinnati, Ohio 45268
    • U.S. Environmental Protection Agency, National Center for Environmental Assessment, 26 W. Martin Luther King Dr., MS 117, Cincinnati, Ohio 45268
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  • Susan B. Norton,

    1. U.S. Environmental Protection Agency, National Center for Environmental Assessment (8623-D), 1200 Pennsylvania Ave. NW, Washington, DC 20460
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  • Susan M. Cormier

    1. U.S. Environmental Protection Agency, National Exposure Research Laboratory, 26 W. Martin L. King Dr., MS 642, Cincinnati, Ohio 45268
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  • Presented at the 20th Annual Meeting, Society of Environmental Toxicology and Chemistry, Philadelphia, Pennsylvania, November 14–18, 1999.

Abstract

Biological surveys have become a common technique for determining whether aquatic communities have been injured. However, their results are not useful for identifying management options until the causes of apparent injuries have been identified. Techniques for determining causation have been largely informal and ad hoc. This paper presents a logical system for causal inference. It begins by analyzing the available information to generate causal evidence; available information may include spatial or temporal associations of potential cause and effect, field or laboratory experimental results, and diagnostic evidence from the affected organisms. It then uses a series of three alternative methods to infer the cause: Elimination of causes, diagnostic protocols, and analysis of the strength of evidence. If the cause cannot be identified with sufficient confidence, the reality of the effects is examined, and if the effects are determined to be real, more information is obtained to reiterate the process.

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