North Carolina State University, Department of Applied Ecology, Raleigh, NC, USA.
North Carolina State University, Department of Applied Ecology, Raleigh, NC, USA.
Sci Total Environ. 2021 Jun 15;773:144757. doi: 10.1016/j.scitotenv.2020.144757. Epub 2021 Feb 3.
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 = -0.64, p ≤ 0.05 in 2012 and r = -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 μg/g dry weight in 2012 and 1540.4-12,605.8 μg/g dry weight in 2013) in surface water (r = 0.58, p < 0.1) and pore water (r = 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.
田纳西河流域的克林奇河位于美国弗吉尼亚州和田纳西州，是上田纳西河流域的一部分，这里拥有北美的大部分淡水生物多样性，包括 46 种现存的淡水贻贝类（贻贝目），其中 20 种受到联邦濒危物种保护。尽管克林奇河具有全球生物意义，但在某些河段，贻贝的种群数量正在减少，无论是在物种丰富度还是丰度方面。本研究的目的是评估成年定居贻贝在克林奇河不同河段暴露于一系列无机和有机污染物压力源的情况，这些河段涵盖了贻贝丰度和健康状况的一系列范围。为了深入了解污染物在贻贝减少中的潜在作用，包括在先前记录的“贻贝减少区”中，我们在连续两年中检查了克林奇河的干流（8 个地点）及其支流（4 个地点）。我们量化并将贻贝中的金属和有机污染物浓度与其相关的生境隔室（底泥、悬浮颗粒沉积物、孔隙水和地表水）相关联。我们发现，定居贻贝中的有机污染物浓度，特别是分析的 42 种多环芳烃（PAHs）的浓度，与所有四个生境（介质）隔室中的 PAH 浓度有关。此外，贻贝组织中的 PAH 浓度（2012 年为 37.8-978.1ng/g 干重，2013 年为 194.3-1073.7ng/g 干重）与河流中贻贝密度的空间格局呈负相关（2012 年 r=-0.64，p≤0.05，2013 年 r=-0.83，p≤0.05），并且在“贻贝减少区”最高。相比之下，成年贻贝中分析的 22 种金属与四个生境隔室中金属变化的空间模式基本没有关系，除了锰（Mn；2012 年为 3630.5-23749.2μg/g 干重，2013 年为 1540.4-12605.8μg/g 干重）在地表水（r=0.58，p<0.1）和孔隙水（r=0.76，p≤0.05）中。本研究表明，PAHs 和 Mn 是克林奇河贻贝的重要污染物胁迫物，它们主要通过格斯特河支流流域输送。因此，未来的保护和管理工作将受益于确定并理想地减轻 PAHs、Mn 和其他当前或遗留的采矿相关污染物对干流及其支流的来源。
