Spatial and Temporal Trends of Freshwater Mussel Assemblages in the Meramec River Basin, Missouri, USA

Abstract

The Meramec River basin in eastcentral Missouri has one of the most diverse unionoid mussel faunas in the central United States with 40 species identified. Data were analyzed from historical surveys to test whether diversity and abundance of mussels in the Meramec River basin Big, Bourbeuse, and Meramec rivers, representing 400 river miles decreased between 1978 and 1997. We found that over 20y, species richness and diversity decreased significantly in the Bourbeuse and Meramec rivers but not in the Big River. Most species were found at fewer sites and in lower numbers in 1997 than in 1978. Federally endangered species and Missouri Species of Conservation Concern with the most severe temporal declines were Alasmidonta viridis, Arcidens confragosus, Elliptio crassidens, Epioblasma triquetra, Fusconaia ebena, Lampsilis abrupta, Lampsilis brittsi, and Simpsonaias ambigua. Averaged across all species, mussels were generally being extirpated from historical sampling sites more rapidly than colonization was occurring. An exception was one reach of the Meramec River between river miles 28.4 and 59.5, where mussel abundance and diversity were greater than in other reaches and where colonization of Margaritiferidae, Lampsilini, and Quadrulini exceeded extirpation. The exact reasons mussel diversity and abundance have remained robust in this 30mile reach is uncertain, but the reach is associated with increased gradients, few long pools, and vertical rock faces, all of which are preferable for mussels. Complete loss of mussel communities at eight sites 16 with relatively diverse historical assemblages was attributed to physical habitat changes including bank erosion, unstable substrate, and sedimentation. Mussel conservation efforts, including restoring and protecting riparian habitats, limiting the effects of instream sand and gravel mining, monitoring and controlling invasive species, and protecting water quality, may be warranted in the Meramec River basin.

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

“…Hinck et al. () found declines in mussel density and attributed the declines to anthropogenic changes in the basin including the loss of riparian vegetation which, along with increased human population growth and the concomitant impacts, led to increased sedimentation, and thus changes in stream morphology leading to decreased habitat stability due to bedload movement. For the one location where mussel abundance remained similar, the authors stated that the exact reason that mussel abundance remained “robust” was unknown but may be due to the fact that despite anthropogenic impacts the geomorphology of this region (higher gradient and fewer pools) may have led to streambed stability.…”

“…Daniel and Brown (2013) also showed that the amount of agricultural lands in the corridor were negatively associated with mussel density and richness. Hinck et al (2012) found declines in mussel density and attributed the declines to anthropogenic changes in the basin including the loss of riparian vegetation which, along with increased human population growth and the concomitant impacts, led to increased sedimentation, and thus changes in stream morphology leading to decreased habitat stability due to bedload movement. For the one location where mussel abundance remained similar, the authors stated that the exact reason that mussel abundance remained "robust" was unknown but may be due to the fact that despite anthropogenic impacts the geomorphology of Lenz, Robertson, Fallon, and Ferrin (2003) examining phosphorus loading into the St. Croix found that storm events provided the largest instantaneous loading rates but that storm events affecting the tributaries in the lower portion of the basin resulted in loads and yields that were relatively small.…”

Early life history and spatiotemporal changes in distribution of the rediscovered Suwannee moccasinshell Medionidus walkeri (Bivalvia: Unionidae)

“…Our findings show the distribution of Medionidus walkeri has changed during the past century, with an overall reduction in range and fewer individuals found during recent surveys, displaying a common pattern observed for freshwater mussels across river systems worldwide (Cosgrove et al 2000, Geist & Kuehn 2005, Haag & Warren 2010, Hinck et al 2012, Jones et al 2014, Lopes-Lima et al 2016, Zipper et al 2016. The observed spatiotemporal changes in distribution appear confined to the periphery of the species' range in the lower Withlacoochee, lower Su wannee, and upper Santa Fe subbasins (Fig.…”

State‐Level Freshwater Mussel Programs: Current Status and a Research Framework to Aid in Mussel Management and Conservation

“…Mussel distribution and diversity in the Meramec River basin declined between 1979 and 1997, and a series of threats were implicated; these included excessive sedimentation, altered hydrology and geomorphology, altered riparian condition, and water quality contaminants (Hinck et al 2012). More specific and spatially explicit identification of threats requires a local knowledge of drivers that have changed in the system.…”