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Development of short-term toxicity test methods to estimate chronic toxicity using the freshwater mussel (Fatmucket, Lampsilis siliquoidea). (Poster)
Citation:
Norberg-King, T., N. Wang, J. Kunz, J. Steevens, E. Hammer, C. Bauer, AND C. Barnhart. Development of short-term toxicity test methods to estimate chronic toxicity using the freshwater mussel (Fatmucket, Lampsilis siliquoidea). (Poster). Twin Ports Freshwater Folk, Duluth, MN, June 05, 2019.
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:
For decades, toxicity tests with aquatic invertebrates have been conducted, and yet a small number of model organisms are routinely used. The US EPA effluent testing program uses short-term chronic freshwater tests (4 to 8d) with cladocerans (Cladocera, Ceriodaphnia dubia), green algae (ýSphaeropleales, Raphidocelis subcapitata) and fish (Cypriniformes, Pimephales promelas). These species have been used extensively in acute and short-term toxicity tests using USEPA standardized methods to assess the hazard of chemicals and effluents in freshwater environments. While USEPA has standardized Hyalella azteca (Amphipoda) and Chironomus dilutus (Dipteran) test methods for sediments; USEPAs effluent and ambient test manuals don’t provide acute or short-term test methods for H. azteca, C. dilutus, mayflies or mussels. To add another sensitive species, we have focused on method development using the fatmucket mussel (Lampsilis siliquoidea) for effluent toxicity assessments. A feeding study was conducted using a mixture of algal and shellfish foods with various starting ages of juveniles (~1, 2, 3 wk old mussels) in both 7d and 10d tests.Growth (shell length) at the feeding rate of 2 mL/2X/d with either 1 or 2 wk old mussels (~0.3-0.4 mm) and 3 mL/2x/d for 3 wk old mussels (~0.5 mm) provided consistent growth. Mean survival was =93% in all feeding treatments except for the 4 ml/1x/d to 1 wk-old mussels (78%). The increase of mussel shell length ranged from 24-52% at 7-d and from 28-60% at 10-d among four feeding treatments. Once the optimum feeding rate was determined, three ages of juveniles were exposed to a reference toxicant (NaCl) for 7d & 10d tests. For both durations, growth (length) was consistently more sensitive than survival, and with juvenile mussels growing over 50% in a short-term test (7d or 10d). The sensitivity to NaCl was mostly the same when tests were initiated with 1, 2 or 3-week-old mussels. To further evaluate the performance and variability in the mussel method, an interlaboratory study with 13 volunteer laboratories from the United States and Canada was conducted using 1-wk-old mussels and NaCl for a 7-d test. In this poster, we will present detailed results of the feeding studies, the relative sensitivity and the interlaboratory results along with a discussion of how the mussel procedure can complement current effluent and receiving water testing. This abstract does not necessarily reflect the views or policies of the US Environmental Protection Agency.