Influences of Water and Sediment Quality and Hydrologic Processes on Mussels in the Clinch River

Abstract

Segments of the Clinch River in Virginia have experienced declining freshwater mussel populations during the past 40 years, while other segments of the river continue to support some of the richest mussel communities in the country. The close proximity of these contrasting reaches provides a study area where differences in climate, hydrology, and historic mussel distribution are minimal. The USGS conducted a study between 2009 and 2011 to evaluate possible causes of the mussel declines. Evaluation of mussel habitat showed no differences in physical habitat quality, leaving water and sediment quality as possible causes for declines. Three years of continuous water‐quality data showed higher turbidity and specific conductance in the reaches with low‐quality mussel assemblages compared to reaches with high‐quality mussel assemblages. Discrete water‐quality samples showed higher major ions and metals concentrations in the low‐quality reach. Base‐flow samples contained high major ion and metal concentrations coincident to low‐quality mussel populations. These results support a conceptual model of dilution and augmentation where increased concentrations of major ions and other dissolved constituents from mined tributaries result in reaches with declining mussel populations. Tributaries from unmined basins provide water with low concentrations of dissolved constituents, diluting reaches of the Clinch River where high‐quality mussel populations occur.

Effects of environmentally relevant mixtures of major ions on a freshwater mussel

“…Prior research has found spatial and temporal associations of elevated TDS concentrations with freshwater mussel declines in the Clinch River in Virginia (Johnson et al, 2014;Price et al, 2014), suggesting that elevated major ions may be causing toxicity in the Clinch River. This idea also applies to the Powell River, where TDS concentrations are substantially higher in the upper reaches of the river and mussel populations have experienced long-term declines at monitoring locations downstream of these high TDS reaches (Ahlstedt et al, 2005;Johnson et al, 2012).…”

“…Independent biological monitoring, initiated in 1979, has documented significant declines of freshwater mussel richness and density in sections of Clinch River and throughout the Powell River (Ahlstedt et al, 2005;Johnson et al, 2012;Jones et al, 2014). Recent research has found a spatial association between elevated TDS concentrations and declining freshwater mussel populations in the Clinch River; reaches of the river experiencing the greatest declines in mussel richness and density have elevated concentrations of major ions relative to other reaches of the river where mussel populations are stable (Johnson et al, 2014). In upper segments of the Powell River, TDS concentrations are greater than at any location in the Clinch River (Price et al, 2011) and severe declines of mussel richness and density have been observed in surveyed reaches of the Powell River located downstream of the high TDS reaches (Ahlstedt et al, 2005;Johnson et al, 2012).…”

Spatial and temporal relationships among watershed mining, water quality, and freshwater mussel status in an eastern USA river

“…Given the spatial extent of surface mining in the upper Powell watershed, it is not surprising that these constituents also are elevated in the Powell River itself. Lindberg et al (2011) also found elevated concentrations of mining-origin constituents in a non-headwater stream influenced by mining, as did Johnson et al (2014) in the Clinch River of southwestern Virginia and eastern Tennessee. Johnson et al (2014) also observed diminishing concentrations of mining-influenced constituents and SC moving downstream from mining influence in the Clinch River of Virginia and Tennessee, which they attributed to dilution caused by influxes of waters from non-mined tributaries.…”

“…Freshwater mussels have experienced high rates of imperilment globally (Williams et al, 1993;Lydeard et al, 2004;Strayer et al, 2004;IUCN, 2015). Mussel declines have occurred in several North American rivers affected by watershed mining (Warren and Haag, 2005;Angelo et al, 2007;Johnson et al, 2014) as well as in the Powell River (Ahlstedt et al, 2015). There is interest in the region to identify specific toxicants that are responsible for the mussel declines that have been observed in streams draining the Appalachian coalfield (Warren and Haag, 2005;Jones et al, 2014) and to determine if such toxicants originate from mining.…”

“…Recent studies have also found fish assemblage structure (Hitt and Chambers, 2014), salamander abundance (Wood and Williams, 2013) and richness (Muncy et al, 2014), and microbial community composition (Bier et al, 2015) to be altered in salinized mining-influenced streams; and freshwater mussel richness and densities to be depressed in salinized river segments . Water borne trace elements often occur at elevated concentrations in association with elevated salinity in such waters (Pond et al, 2008;Lindberg et al, 2011;Pond et al, 2014) and are also of concern due to potential biotic impacts (Palmer et al, 2010;Johnson et al, 2014). Depressed aquatic communities have also been observed in salinized freshwater bodies of other world regions (Cañedo-Argüelles et al, 2013).…”