Influence of hyporheic exchange, substrate distribution, and other physically linked hydrogeomorphic characteristics on abundance of freshwater mussels

Abstract

Both endangered and non‐endangered unionid mussels are heterogeneously distributed within the Allegheny River, Pennsylvania. Mussel populations vary from high to low density downstream of Kinzua Dam, and the direction, amount, and range of hyporheic exchange (seepage) at the sediment–water interface were suspected to influence their distribution and abundance. Nineteen hydrogeomorphic variables, including the quantification of seepage metrics, substrate size, river stage, river discharge, and shear stress, were measured at five reaches on the Allegheny River within 80 km downstream of Kinzua Dam. Analysis revealed significant (α = 0·05) non‐linear correlations between mussel population density and directional mean seepage (positive relationship), river width (positive relationship), and median substrate size (negative relationship). Specifically, seepage findings showed that increases in upward seepage and decreases in the overall range of seepage related to increases in mussel population density. River width, directional mean seepage, and median substrate size were also found to co‐vary with marginal significance (α = 0·1), making their individual influences on mussel population density uncertain. Absolute mean seepage, water depth, hydraulic head, temperature differences between the surface water and substrate, and other substrate metrics besides median grain size were not found to significantly correlate to mussel population density. Considering the physical processes often linking seepage to other explanatory variables, future research in seepage–mussel relationships should work to isolate the mechanistic influence of hyporheic exchange independently from its common covariation with substrate size and geomorphology. Copyright © 2014 John Wiley & Sons, Ltd.

Influence of groundwater on distribution of dwarf wedgemussels (<i>Alasmidonta heterodon</i>) in the upper reaches of the Delaware River, northeastern USA

“…Therefore, few studies of exchange between groundwater and surface water have been successfully conducted in such coarse-grained sediments. Compared to those that have (e.g., Rosenberry et al, 2012;Fritz et al, 2009;Klos et al, 2015), values for point measurements of seepage exchange at these three sites on the Delaware River were not particularly large. This indicates that hyporheic exchange is perhaps smaller than would be expected along M reaches, given the coarseness of the bed.…”

“…Few studies have related groundwater discharge with mussel abundance and species richness. A study conducted in a river with similarly coarse sediment indicated a relation between mussel population density and upward seepage rate (Klos et al, 2015), but upward seepage in that setting was primarily driven by hyporheic exchange. The net upward seepage at DWM sites in the Delaware River, although clearly influenced by hyporheic exchange, is primarily the result of area-wide groundwater discharge as evidenced by substantially faster reach-averaged upward seepage and also colder water along M reaches relative to N reaches.…”

Long‐term decline of native freshwater mussel assemblages in a federally protected river

“…Klos et al. () findings support this view; they found a decrease in mussel density with increasing median sediment size. In addition, they suggested that the smallest size sediment they encountered was well within the range normally associated with higher mussel density; thus, the decrease with larger median sediment size could indicate an upper limit on the sediment size preferred by unionoids.…”

“…Other studies have also noted density and richness increasing downstream of dams (e.g. Vaughn and Taylor (); Klos, Rosenberry, and Nelson (). This has especially been true below small dams (Haag, ; Hornbach et al., ; Singer & Gangloff, ) where higher densities are attributed to reservoir derived temperature and food enhancements (Gangloff, Hartfield, Werneke, & Feminella, ; Hornbach et al., ).…”

Characterizing Land Use Impacts on Channel Geomorphology and Streambed Sedimentological Characteristics

“…The importance of channel geomorphology and stream substrate composition with regards to stream habitat has been well-documented [1][2][3][4][5]. Previous studies indicated that channel geomorphology and stream substrate are important aspects of stream physical habitat [6][7][8]. For example, substrate is a medium for settlement by propagules [9].…”