You are here:
State of the science of mayfly ecotoxicity testing
Citation:
Wirtz, J., M. McCoole, P. Sibley, L. Lagadic, D. Soucek, T. Norberg-King, AND I. Roessink. State of the science of mayfly ecotoxicity testing. SETAC North America, Sacramento, CA, November 04 - 08, 2018.
Impact/Purpose:
Clean Water Act (CWA) implementation starts with the development of water quality criteria to protect uses, such as aquatic life. While aquatic life is exposed to innumerable chemical mixtures in the nation’s waters, EPA has developed just 45 numeric aquatic life criteria for use in National Pollution Discharge Elimination System (NPDES) permits and assessment of the nation’s waters. There is an urgent need to better protect aquatic life (including species federally-listed per the Endangered Species Act, or ESA) by establishing additional test methods for sensitive aquatic life. Historically, the choice of invertebrate species used in most current water and sediment toxicity test protocols represent a combination of practical and ecological considerations. This has led to the development of widely applied toxicity test protocols that incorporate reliable, though not necessarily highly sensitive, test species. Early exploration of candidate species for toxicity testing included evaluation of EPT (Ephemeroptera, Plecoptera, Trichoptera) taxa. However, many of these were found to be difficult to culture (e.g., many EPT taxa require flowing water), biological requirements were not well known, most would not reproduce under laboratory conditions, and many were sensitive to the laboratory environment (often failing to meet control test acceptability criteria during tests). In recognition of recent advances in culturing and application in aqueous and sediment-based toxicity testing of EPT species, a project was initiated to report on the state of the science for the application of mayflies in ecotoxicity testing. Key goals of the project include the identification and prioritization of knowledge gaps that can serve as areas for future research, the assessment of the prospect for routine incorporation of mayflies in toxicity testing, and the creation of standardized toxicity test protocols followed by a mayfly workshop in September. When we have additional methods available, they can be used by EPA, state, and tribal NPDES permitting programs and can support the completion of ecological risk assessments conducted in accordance with the CWA, ESA and other laws.
Description:
The historical choice of invertebrate species used in most current water and sediment toxicity test protocols represents a combination of practical (e.g., amenity to year-round laboratory culturing, ease of maintenance, and regulatory acceptability) and ecological (e.g., geographic and habitat representation, feeding habits and relative sensitivity) considerations. This has led to the development of widely applied toxicity test protocols that incorporate reliable, though not necessarily highly sensitive, test species. Early exploration of candidate species for toxicity testing included evaluation of EPT (Ephemeroptera, Plecoptera, Trichoptera) taxa. However, many of these were found to be difficult to culture (e.g., many EPT taxa require flowing water), biological requirements were not well known, most would not reproduce under laboratory conditions, and many were sensitive to the laboratory environment (often failing to meet control test acceptability criteria during tests). Such early efforts with EPT species were therefore largely abandoned in favor of more pragmatic species (e.g., Daphnia magna, Ceriodaphnia dubia, Hyalella azteca, Chironomus dilutus/riparius) now used in most of the standard toxicity test protocols. However, field and laboratory studies have consistently shown that the EPT group of insects contain some of the most sensitive species to environmental contaminants. In recognition of recent advances in culturing and application in aqueous and sediment-based toxicity testing of EPT species, a project was initiated to report on the state of the science for the application of mayflies in ecotoxicity testing. The first part of the project involved a literature search for peer-reviewed and grey literature on Ephemeroptera species that covers their ecology, species’ ranges, relative sensitivity among mayfly species used in toxicity tests, and a comparison of the sensitivity of mayflies to standard aquatic toxicity test species. Key goals of the project include the identification and prioritization of knowledge gaps that can serve as areas for future research, the assessment of the prospect for routine incorporation of mayflies in toxicity testing, and the creation of standardized toxicity test protocols.