Threats to freshwater mussels: The interactions of water temperature, velocity and total suspended solids on ecophysiology and growth

Abstract

Freshwater unionid mussels are ecosystem engineers that are highly endangered in part because of land-use changes that have altered their habitat and negatively impacted their ecophysiology. The environmental factors that affect mussels do not act alone and may be better understood using a multiple-stressor approach. We examine how changes in water temperature, turbidity (total suspended solids; TSS) and water velocity affected the clearance rates (CR), oxygen consumption rates (OC), and resultant scope for growth (SFG) of Lampsilis siliquoidea in laboratory flow chamber experiments. The CR, OC and SFG of L. siliquoidea increased with acclimation temperature and velocity, and decreased with TSS concentration and acute temperature exposure, although these responses were more complicated when factors were combined. The primary factor affecting CR and OC varied with acclimation temperature, with warmer temperature and high TSS leading to strong declines in clearance rates. A worst-case scenario would involve a summer season where temperatures and TSS loads are above-average, and water velocities are either below- or above- average, which are likely under increased frequencies of storm, flood, or drought events due to climate change. Conservation measures should focus on protecting aquatic systems during these times and also use a multistressor approach to determine how environmental factors interact in efforts to protect and recover freshwater mussel populations.