Influence of urban tributaries on freshwater mussel populations in a biologically diverse piedmont (USA) stream

Abstract

The Southeastern USA is currently experiencing a period of rapid growth of human populations that is likely having profound effects on the region's unique aquatic biota. Using both survey data and experimental protocols, we assessed the influences of water and habitat quality on freshwater mussel populations in a small Piedmont stream. Chewacla Creek is a high-quality stream located near the rapidly growing towns of Auburn and Opelika in east-central Alabama. From 1999 to 2007 we monitored freshwater mussel populations and measured substrate and water chemistry variables in Chewacla Creek. Surveys revealed that mussel abundance decreased substantially concomitant with degraded habitat and water quality downstream of three highly urbanized tributaries. We conducted sentinel trials using adult mussels (Villosa lienosa) in Chewacla Creek and a tributary (Parkerson Mill Creek) that receives wastewater discharge. Sentinel mussels were placed in cages at three locations downstream of the effluent discharge point and at one upstream site (control). Sentinel mussels exposed to wastewater discharge exhibited lower survival rates compared to control animals. Together, survey and experimental data suggest that degraded tributary subcatchments may fragment mussel populations in highquality streams. Moreover, our data indicate that protection of sensitive aquatic taxa necessitates effective management of water quality across large spatial scales.

Urbanization and a threatened freshwater mussel: evidence from landscape scale studies

“…Other studies have also suggested high flows are important to unionids: mussel communities differ between ''flashy'' and stable rivers (DiMaio & Corkum, 1995), mussel beds occur in flow refugia (Strayer, 1999), high shear forces limit juvenile settlement (Layzer & Madison, 1995), and mussels grow slower in years with high flow events (Rypel et al, 2009). Urbanization also impacts lotic mussel communities through stream bed erosion and channel degradation (Gangloff & Feminella, 2007) or through producing non-point source pollutants that lower the survival or growth of mussels (Gangloff et al, 2009). In contrast, wetlands and riparian vegetation dampen these effects through water storage, filtering, and increased water residence time.…”

“…Their loss from lotic systems could seriously affect ecosystem function, as they provide food resources and structure for other macro-invertebrates (Vaughn et al, 2004;Howard & Cuffey, 2006) and influence nutrient cycling (Vaughn et al, 2008). Threats to mussels in the southeastern United States, where they are most diverse, include impoundments, increased agricultural use or urbanization of the watershed (Diamond et al, 2002;Gillies et al, 2003;Gangloff & Feminella, 2007), loss or fragmentation of riparian forest cover (Gagnon et al, 2006;Hopkins, 2009), and pollution (Gangloff et al, 2009).…”

Scale‐dependent longitudinal patterns in mussel communities

“…Further research is necessary to understand the influence of urbanisation on mussel communities (see Brown et al, 2010). Previous studies have shown shifts in aquatic insect assemblages in catchments with >10% impervious surface cover (Paul & Meyer, 2001;Roy et al, 2003;Utz, Hilderbrand & Boward, 2009), which suggests that changes in hydrology, increased nutrient loads and increased sediment loads from urbanisation could also alter mussel community composition (Gangloff et al, 2009). Because the rivers in this study are threatened by planned municipal water extractions (Oklahoma Water Resources Board, 2011) and further dam construction (Vaughn & Taylor, 1999;Galbraith et al, 2010), an understanding of factors influencing mussel community composition is critical to future river management plans.…”

Impacts of artificial structures on the freshwater pearl mussel Margaritifera margaritifera in the River Dee, Scotland

“…Could tributary inputs of poor quality water be sufficient to affect freshwater pearl mussel distribution, given the high volumes of receiving waters in the main stem of the River Dee? Gangloff et al () concluded that degraded tributary sub‐catchments may fragment mussel populations in high‐quality streams; certainly the diluting effect with distance downstream from such inputs would be consistent with the linear relationship observed. The downstream impacts of a tributary confluence on sediment size (Rice and Church, ), bed instability, bed scour and deposition could also be influential, although these impacts would be rather localized.…”

“…Freshwater mussels are particularly at risk (Ciccotelli et al , ) because they are stationary and filter feed on suspended particles. Unionids have been shown to be absent from reaches downstream of wastewater treatment facilities (Horne and McIntosh, ; Goudreau et al , ) or exhibit reduced survival (Gangloff et al , ). The highly sensitive freshwater pearl mussel might therefore be expected to be affected adversely by direct toxicity, sedimentation, or eutrophication, especially during high flows where discharges are via CSOs, or low flows when water quality issues are exacerbated.…”