Differential sediment stability for two federally threatened and one common species of freshwater mussels in Southeastern Coastal Plain Streams, USA

Abstract

The current study examined differences in sediment stability preferences for two federally threatened and a locally common mussel species’ habitats in the Choctawhatchee River watershed located in southeastern Alabama and northwestern Florida. Relative shear stress (RSS), the ratio of shear stress to critical shear stress, was calculated for individuals of two threatened mussel species, Fusconaia burkei (N = 94), and Pleurobema strodeanum (N = 201), and a common mussel species, Elliptio pullata (N =94). Relative shear stress is related to sediment movement and deposition as sediment movement takes place when RSS > 1. Mussels were collected and RSS measured at each individual mussel location (N = 389). The Kruskal–Wallis H-test and/or Mann–Whitney U-test found that RSS for the target-threatened species’ habitats were significantly higher than that for E. pullata at all sites (p < 0.05). Spearman’s rank correlation found significant negative correlations between shear stress and total mussel abundance at all sites (p < 0.05). Streams selected in our study were typical representatives of high-quality southeastern Coastal Plain streams. Therefore, we suggest that our findings of differences in hydraulic instability of mussel habitats among species may represent similar conditions for other rare and endangered species. Sediment movement and deposition may be linked to the decline and consequent federal listing of the target-threatened species under our study.