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Method development for conducting short-term effluent tests with freshwater mussel (Fatmucket, Lampsilis siliquoidea)
Citation:
Wang, N., J. Kunz, J. Steevens, T. Norberg-King, E. Hammer, C. Bauer, AND M. Barnhart. Method development for conducting short-term effluent tests with freshwater mussel (Fatmucket, Lampsilis siliquoidea). SETAC North America, Sacrsamento, 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. 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.” Currently, EPA primarily relies on short-term chronic toxicity testing methods for only two animals and one plant species in the NPDES WET program to assess whether effluents or waters comply with this “no toxics” provision of the CWA. 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. To best accomplish this goal, WET methods for new species could be developed, validated, and promulgated at 40 CFR Part 136. The fatmucket (Lampsilis siliquoidea) is found in six of the EPA Regions and Canada and has been demonstrated to be among the most sensitive of all aquatic species to some contaminants, including ammonia, chloride, sulfate, potassium, copper, nickel, and zinc. Studies with the fatmucket mussel to develop short-term 7-day testing procedures like those used determining effluent toxicity have been conducted to determine optimum feeding rates and the most sensitive stage of the juvenile mussels in 7- and 10-d exposures using survival and growth of different ages of the juvenile mussels. We are now starting an interlaboratory study to evaluate the performance and variability in the newly developed mussel testing method with 13 volunteer laboratories to test the method we have developed. Once the new methods have been demonstrated to be sensitive and reliable for effluents and receiving waters, they can be proposed for approval for use by EPA, state, and tribal NPDES permitting programs to support the completion of ecological risk assessments conducted in accordance with the CWA, ESA and other laws.
Description:
Short-term (6-8 d) freshwater toxicity test methods have been promulgated by the USEPA for estimating chronic toxicity of effluent and receiving water. These methods include a fish (Pimephales promelas), a cladoceran (Ceriodaphnia dubia), and a green alga (Raphidocelis subcapitata). Recent studies have demonstrated that a unionid mussel (fatmucket, Lampsilis siliquoidea) is one of the more sensitive species for ammonia, some metals, and major ion salts. Therefore, use of mussels as an additional species holds promise for effluent toxicity assessments. The objective of this study was to develop standard effluent test methods with fatmucket by, initially, determining optimum feeding rates and starting ages of juvenile mussels (~1-, 2-, and 3-wk old) in a 7- and 10-d feeding study; afterwards, assessing the sensitivity of the three ages of mussels in 7- and 10-d NaCl toxicity tests; and finally evaluating the performance and variability in the mussel methods through an interlaboratory study. For the feeding study, an algal mixture (~510 nl cell volume/mL) was prepared by mixing a commercially available algal concentrate and shellfish diet in test water (diluted well water at a hardness of 100 mg/L CaCO3). The mussels were fed at four rates in the feeding study: adding 1, 2, or 3 mL of algal mixture twice daily or 4 mL once daily into each replicate chamber containing 200 mL of water. Mean survival was =93% in all feeding treatments except for the 4 mL fed once a day to 1-wk-old mussels (78%). The increase of mussel shell length ranged from 24 to 52% at test day 7 and from 28 to 60% at test day 10 among the four feeding treatments. The best growths (length) were observed at the feeding rate of 2 mL twice daily in treatments started with 1- to 2-wk-old mussels (~0.3 to 0.4 mm length), and at a higher feeding rate of 3 mL 2 times daily for 3-wk-old mussels (~0.5 mm length). The optimum feeding rates were used in the 7- and 10-d NaCl toxicity tests started with the 1-, 2-, or 3-wk-old mussels. For both test durations, the growth was consistently more sensitive than survival, and the sensitivity to NaCl was essentially the same among the three ages of mussels. An interlaboratory study has been organized and will be performed in thirteen volunteer laboratories from the United States and Canada, using 1-wk-old fatmucket in a 7-d NaCl exposure.