Browsing by Author "Beaty, Braven"

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    Combined effects of copper, nickel, and zinc on growth of a freshwater mussel (Villosa iris) in an environmentally relevant context
    Timpano, Anthony J.; Jones, Jess W.; Beaty, Braven; Hull, Matthew; Soucek, David J.; Zipper, Carl E. (Elsevier, 2022-01)
    Trace metals rarely contaminate freshwaters independently, hence regulatory limits based on single-metal toxicity may be underprotective of aquatic life. This could be especially the case for rare and sensitive fauna like freshwater mussels, such as those suppressed in the Clinch and Powell Rivers in eastern USA where trace metals are long-term contaminants but at concentrations below regulatory limits. We hypothesized metal mixtures may be exerting combined effects on mussels, resulting in greater toxicity than would be predicted based on single-metal exposures. To test that hypothesis, we conducted two experiments exposing juvenile rainbow mussels (Villosa iris) for 42 days to dissolved copper, nickel, and zinc, individually and in three-metal mixtures, in an environmentally-relevant context of water with chemistry (hardness 155 mg/L as CaCO3, dissolved organic carbon 1.7-2.3 mg/L, pH 8.4) similar to that of the Clinch River, which receives alkaline mine drainage. We used a toxic unit approach, selecting test concentrations based on literature values for the lower of 28-day survival or growth (length) effect concentrations for Villosa iris or Lampsilis siliquoidea (fatmucket). Our first experiment confirmed survival and growth effects when acute and chronic water quality criteria, respectively, are approached and/or exceeded. Our second experiment, at lower concentrations, showed no effects on survival but combined effects on growth were evident: a mixture of Cu, Ni, and Zn (7.2 +/- 1.2, 65.3 +/- 6.1, 183 +/- 32 mu g/L, respectively) inhibited growth (dry weight) by 95% versus 73%, 74%, and 83% inhibition for single-metal exposures to Cu, Ni, and Zn of similar concentration (8.0 +/- 1.1, 63.5 +/- 4.8, 193 +/- 31 mu g/L, respectively). Furthermore, a mixture of Cu, Ni, and Zn with individual concentrations 21%, 29%, and 37% of their water quality criteria (3.4 +/- 1.2, 21.8 +/- 1.8, and 62.1 +/- 8.4 mu g/L, respectively) inhibited growth (dry weight) by 61% relative to controls. Our observation of combined effects suggests that regulatory limits based on single-metal toxicity may be underprotective of freshwater mussels when multiple metals are present.
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    Understanding the influence of multiple pollutant stressors on the decline of freshwater mussels in a biodiversity hotspot
    Cope, W. Gregory; Bergeron, Christine M.; Archambault, Jennifer M.; Jones, Jess W.; Beaty, Braven; Lazaro, Peter R.; Shea, Damian; Callihan, Jody L.; Rogers, Jennifer J. (2021-06-15)
    The Clinch River watershed of the upper Tennessee River Basin of Virginia and Tennessee, USA supports one of North America's greatest concentrations of freshwater biodiversity, including 46 extant species of native freshwater mussels (Order Unionida), 20 of which are protected as federally endangered. Despite the global biological significance of the Clinch River, mussel populations are declining in some reaches, both in species richness and abundance. The aim of this study was to evaluate the exposure of adult resident mussels to a suite of inorganic and organic contaminant stressors in distinct sections of the Clinch River that encompassed a range of mussel abundance and health. To provide insight into the potential role of pollutants in the decline of mussels, including within a previously documented "zone of mussel decline", the mainstem Clinch River (8 sites) and its tributaries (4 sites) were examined over two consecutive years. We quantified and related metals and organic contaminant concentrations in mussels to their associated habitat compartments (bed sediment, suspended particulate sediment, pore water, and surface water). We found that concentrations of organic contaminants in resident mussels, particularly the suite of 42 polycyclic aromatic hydrocarbons (PAHs) analyzed, were related to PAH concentrations in all four habitat (media) compartments. Further, PAH concentrations in mussel tissue (range 37.8-978.1 ng/g dry weight in 2012 and 194.3-1073.7 ng/g dry weight in 2013) were negatively related to the spatial pattern in mussel densities (r(s) = -0.64, p <= 0.05 in 2012 and r(s) = -0.83, p <= 0.05 in 2013) within the river, and were highest in the "zone of mussel decline". In contrast, the suite of 22 metals analyzed in resident mussels were largely unrelated to the spatial pattern of variation of metals in the four habitat compartments except for Manganese (Mn; range 3630.5-23,749.2 mu g/g dry weight in 2012 and 1540.4-12,605.8 mu g/g dry weight in 2013) in surface water (r(s) = 0.58, p < 0.1) and pore water (r(s) = 0.76, p <= 0.05). This study revealed that PAHs and Mn are important pollutant stressors to mussels in the Clinch River and that they are largely being delivered through the Guest River tributary watershed. Accordingly, future conservation and management efforts would benefit by identifying, and ideally mitigating, the sources of PAHs, Mn, and other current or legacy mining associated pollutants to the mainstem river and its tributaries. (C) 2021 Elsevier B.V. All rights reserved.