An evaluation of freshwater mussel toxicity data in the derivation of water quality guidance and standards for copper

Abstract

The state of Oklahoma has designated several areas as freshwater mussel sanctuaries in an attempt to provide freshwater mussel species a degree of protection and to facilitate their reproduction. We evaluated the protection afforded freshwater mussels by the U.S. Environmental Protection Agency (U.S. EPA) hardness‐based 1996 ambient copper water quality criteria, the 2007 U.S. EPA water quality criteria based on the biotic ligand model and the 2005 state of Oklahoma copper water quality standards. Both the criterion maximum concentration and criterion continuous concentration were evaluated. Published acute and chronic copper toxicity data that met American Society for Testing and Materials guidance for test acceptability were obtained for exposures conducted with glochidia or juvenile freshwater mussels. We tabulated toxicity data for glochidia and juveniles to calculate 20 species mean acute values for freshwater mussels. Generally, freshwater mussel species mean acute values were similar to those of the more sensitive species included in the U.S. EPA water quality derivation database. When added to the database of genus mean acute values used in deriving 1996 copper water quality criteria, 14 freshwater mussel genus mean acute values included 10 of the lowest 15 genus mean acute values, with three mussel species having the lowest values. Chronic exposure and sublethal effects freshwater mussel data available for four species and acute to chronic ratios were used to evaluate the criterion continuous concentration. On the basis of the freshwater mussel toxicity data used in this assessment, the hardness‐based 1996 U.S. EPA water quality criteria, the 2005 Oklahoma water quality standards, and the 2007 U.S. EPA water quality criteria based on the biotic ligand model might need to be revised to afford protection to freshwater mussels.

Evaluation of acute copper toxicity to juvenile freshwater mussels (fatmucket, Lampsilis siliquoidea) in natural and reconstituted waters

“…March et al [8] compiled freshwater mussel data from highquality toxicity tests. Among the data, acute 96-h copper EC50s for newly transformed juveniles of eight mussel species Fig.…”

“…Specifically, the median effective concentrations (EC50s) for mussels were 30 to 75% below the final acute values used to derive the U.S. Environmental Protection Agency (U.S. EPA) hardness-dependent acute water quality criterion (WQC) for copper [7]. In addition, March et al [8] calculated 14 mussel genus mean acute values (GMAVs) for copper and found that when including mussel data in the database used to derive the hardness-dependent WQC for copper [7], GMAVs for mussels accounted for the first three lowest values or 10 of the 15 lowest values.…”

“…Most copper toxicity tests with mussels have been conducted in reconstituted waters with almost no organic matter and a limited range of water quality characteristics (e.g., hardness, alkalinity, or pH [5,[8][9][10]). However, some studies with other freshwater organisms have indicted that acute toxicity of copper is affected by various water characteristics, including hardness, alkalinity, pH, and dissolved organic carbon [11][12][13][14][15][16][17].…”

“…The U.S. EPA recently used a BLM to revise the WQC for copper [20], and this BLM-based WQC for copper is more protective of mussel species than the hardness-dependent WQC [5,8,9]. For example, the BLM-based final acute value for the reconstituted hard water, which was often used to conduct acute copper toxicity tests with mussels, is about four times lower than the hardness-based final acute value in the exposure water [5].…”

Acute sensitivity of a broad range of freshwater mussels to chemicals with different modes of toxic action

“…However, mussels are generally underrepresented in toxicity databases used for the development of water quality criteria, standards, and other environmental guidance values [6,7,12,13]. In addition, the limited mussel data available have been generated mostly from toxicity tests with a few species of the taxonomic tribe Lampsilini [5][6][7][8][9][10][11][12][13][14][15][16]. Studies with broader phylogenetic representation are needed to understand the range of sensitivity among freshwater mussels, compare the overall sensitivity of mussels to other freshwater species, and evaluate the degree to which existing or proposed environmental guidance values are protective of mussels.…”