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Method development for short-term effluent tests with a freshwater mussel (Fatmucket Lampsilis siliquoidea)
Citation:
Wang, N., J. Kunz, J. Steevens, C. Barnhart, T. Augspurger, S. Dunn, D. Martinez, E. Hammer, C. Bauer, AND T. Norberg-King. Method development for short-term effluent tests with a freshwater mussel (Fatmucket Lampsilis siliquoidea). FMCS International Freshwater Mollusk, Verbania, N/A, ITALY, September 16 - 20, 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 testing methods have been promulgated by the US Environmental Protection Agency for estimating chronic toxicity of effluent and receiving water using three standard species: a fish (Pimephales promelas), a cladoceran (Ceriodaphnia dubia), and a green alga (Raphidocelis subcapitata). Unionid mussels are among the most sensitive species to a variety of contaminants, including ammonia, some metals, and major ion salts; use of mussels as an additional species holds promise for effluent toxicity assessments. We developed toxicity testing methods using juvenile mussels because this life stage is more sensitive to contaminants. Between 2012 and 2016, we evaluated the sensitivity of two species of mussels (Villosa constricta and Lampsilis siliquoidea) and the two standard test species (C. dubia and P. promelas) to field-collected effluents and laboratory-prepared mock effluents in 7-d exposures. These studies showed that both mussels were equally or more sensitive to the effluents compared to the two standard test species. In 2017, we refined the mussel testing method with L. siliquoidea, a commonly tested mussel, by determining optimum feeding rates and ages of juvenile mussels (1-, 2-, and 3-wk old) in a 7- and 10-d feeding study and by assessing the sensitivity of the three ages of mussels in 7- and 10-d reference toxicant (NaCl) tests. In the NaCl tests, growth (length) was a more sensitive endpoint than survival, and sensitivity to NaCl was essentially the same among the three ages of mussels. Finally, in 2018, an interlaboratory study was performed in 13 volunteer laboratories from the USA and Canada to evaluate the variability in 7-d NaCl toxicity tests with 1-wk-old fatmucket. We present the results of studies on the comparative sensitivity, feeding, and interlaboratory variability, as well as a discussion of the mussel test methods that complement current effluent testing.