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Mayflies in ecotoxicity testing: methodological needs and knowledge gaps
Citation:
Sibley, P., L. Lagadic, M. McCoole, T. Norberg-King, I. Roessink, D. Soucek, T. Watson-Leung, AND J. Wirtz. Mayflies in ecotoxicity testing: methodological needs and knowledge gaps. Integrated Environmental Assessment and Management. Allen Press, Inc., Lawrence, KS, 16(2):291-293, (2020). https://doi.org/10.1002/ieam.4252
Impact/Purpose:
Clean Water Act (CWA) implementation starts with the development of water quality criteria to protect uses, such as aquatic life. EPA’s National Pollution Discharge Elimination System (NPDES) permits system provides protection for our nation’s waters with water quality criteria, whole effluent toxicity and bioassessments. As such, whole effluent toxicity (WET) methods are used to assess whether chemical mixtures of effluents and ambient waters are causing toxicity to aquatic life, thereby filling a key role in meeting the CWA goal of “no toxics in toxic amounts.” While EPA currently relies a small number (one cladoceran, one fish, one plant species) for assessing toxicity and other groups of organisms have been identified as potential test species. Additional methods for sensitive species from different taxonomic groups are needed to ensure that the NPDES WET program has new tools to assess whether effluents or waters comply with this “no toxics” provision of the CWA.
Description:
SUMMARY OF EDITORIAL: Insects within the orders Ephemeroptera, Plecoptera, and Trichoptera (“EPT” insects) comprise some species that are the most sensitive to environmental chemicals. However, a lack of robust laboratory toxicity data for insects, particularly for chronic exposures, has resulted in uncertainty as to whether water quality criteria based on non-insect laboratory toxicity data are adequately protective of sensitive aquatic insects. The choice of invertebrate species used in current standard water and sediment toxicity tests represents a combination of practical (e.g., ease of culturing and maintenance; regulatory acceptability) and ecological (e.g., geographic and habitat representation; relative sensitivity) considerations. Early efforts were, therefore, largely abandoned in favor of test protocols that incorporated pragmatic and reliable, though not necessarily highly sensitive, species (e.g., Daphnia magna, Ceriodaphnia dubia, Hyalella azteca, Chironomus dilutus [previously tentans]), which are now used in the majority of tests for routine toxicity testing and regulatory assessments. In recent years, there has been renewed interest in incorporating sensitive insect taxa in toxicity testing and this effort has largely focused on mayflies due, in part, to the high sensitivity of some species to a range of chemical classes. In recognition of the growing interest in the application of mayflies in aquatic toxicity testing, a one-day virtual workshop was held in September 2018 to identify and discuss knowledge gaps that constrain advancements in the use of culture-based and field-collected mayfly species in toxicity testing. This editorial highlight the findings of that workshop and outlines some priority needs in mayfly ecotoxicity testing.
