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Evaluation of Chronic Effects of Potassium Chloride and Nickel on Survival, Growth, and Reproduction of a Unionid Mussel (Lampsilis siliquoidea)
Citation:
Wang, N., J. Kunz, D. Cleveland, R. Dorman, J. Steevens, S. Raimondo, T. Augsberger, AND C. Barnhardt. Evaluation of Chronic Effects of Potassium Chloride and Nickel on Survival, Growth, and Reproduction of a Unionid Mussel (Lampsilis siliquoidea). ENVIRONMENTAL TOXICOLOGY AND CHEMISTRY. Society of Environmental Toxicology and Chemistry, Pensacola, FL, 43(5):1097–1111, (2024). https://doi.org/10.1002/etc.5843
Impact/Purpose:
Freshwater mussels can live for over 60 years; however prior to the current study there were no validated test protocols available to assess chemical impacts on mussel reproduction. This research developed a novel partial life cycle test for mollusks to evaluate chemical impacts to reproductive endpoints. The partial life cycle test was conducted in conjunction with shorter-term tests conducted on juvenile mussels in 4- and 12-week assays using a common chemical to compare the sensitivity of reproductive endpoints against those measured in shorter duration tests conducted on juveniles. The sensitivity of biomass as an endpoint to KCl or Ni from standard chronic 4-wk tests was equal to or greater than reproductive endpoints from partial life-cycle tests. Extending the chronic test duration from 4 to 12 wks greatly increased the toxicity of KCl to juvenile mussels but did not substantially change the toxicity of Ni. The research concluded that juvenile mussels in standard chronic 4-wk toxicity tests may sufficiently represent the sensitivity of other life stages from the partial life-cycle tests; however, the response of juveniles in a longer-term 12-wk exposure may reflect more accurate estimates of inherent sensitivity to some toxicants.
Description:
The ASTM International standard test method for freshwater mussels (E2455-13) recommends 4-week toxicity testing with juveniles to evaluate chronic effects on survival and growth. However, concerns remain that the method may not adequately address the sensitivity of mussels to longer term exposures (>4 weeks), particularly in relation to potential reproductive impairments. No standard method directly evaluates toxicant effects on mussel reproduction. The objectives of the present study were to (1) evaluate toxicity endpoints related to reproduction in fatmucket (Lampsilis siliquoidea) using two common reference toxicants, potassium chloride (KCl) and nickel (Ni); (2) evaluate the survival and growth of juvenile fatmucket in standard 4-week and longer term (12-week) KCl and Ni tests following a method refined from the standard method; and (3) compare the sensitivity of the reproductive endpoints with the endpoints obtained from the juvenile mussel tests. Reproductive toxicity tests were conducted by first exposing female fatmucket brooding mature larvae (glochidia) to five test concentrations of KCl and Ni for 6 weeks. Subsamples of the glochidia were then removed from the adults to determine three reproductive endpoints: (1) the viability of brooded glochidia; (2) the viability of free glochidia in a 24-h exposure to the same toxicant concentrations as their mother; and (3) the success of glochidia parasitism on host fish. Mean viability of brooded glochidia was significantly reduced in the high KCl concentration (26 mg K/L) relative to the control, with a 20% effect concentration (EC20) of 14 mg K/L, but there were no significant differences between the control and any Ni treatment (EC20 > 95 µg Ni/L). The EC20s for viability of free glochidia after the additional 24-h exposure and parasitism success were similar to the EC20s of brooded glochidia. The EC20s based on the most sensitive biomass endpoint in the 4-week juvenile tests were 15 mg K/L and 91 µg Ni/L, similar to or greater than the EC20s from the reproductive KCl and Ni tests, respectively. When exposure duration in the juvenile tests was extended from 4 to 12 weeks, the EC20s decreased by more than 50% in the KCl test but by only 8% in the Ni test. Overall, these results indicate that a standard 4-week test with juvenile mussels can prove effective for estimating effects in chronic exposures with different life stages although a longer term 12-week exposure with juvenile mussels may reveal higher sensitivity of mussels to some toxicants, such as KCl.
URLs/Downloads:
DOI: Evaluation of Chronic Effects of Potassium Chloride and Nickel on Survival, Growth, and Reproduction of a Unionid Mussel (Lampsilis siliquoidea)