Cooperative Fish and Wildlife Research Units Program: North Carolina
Education, Research and Technical Assistance for Managing Our Natural Resources

Freshwater mussels possess a suite of traits that may make them highly vulnerable to climate change. These traits include their patchy distribution, phenological traits (i.e., spatial and temporal dependence of their larvae on host fish), limited dispersal, limited mobility, their threatened status, and the fact that they inhabit fragmented landscapes. Recent research in our laboratory has determined that some freshwater mussel species are already living close to their upper thermal tolerances and thus, may be at risk from increasing surface water and bed sediment temperatures and altered flow regimes due to climate change and associated fluctuations. A primary objective of this project will be to use our newly developed mussel vulnerability and risk threshold data in downscaled watershed and instream regional models so that federal and state natural resource managers will be able to forecast species responses to climate change over the next 30-50 years and to develop adaptation strategies to mitigate the adverse effects. Secondary objectives will be to refine these models and to generate new models with empirical data produced from integrated laboratory and field studies of mussel temperature sensitivities in water and sediment, and instream flow and habitat assessments for mussels. - Evaluate the relative sensitivity of juvenile native freshwater mussels to a range of common and extreme water temperatures that may be encountered during summer periods in streams in the southeastern and central United States by conducting water-based laboratory tests with species that represent each of the two major subfamilies (Ambleminae and Unioninae) of mussels. These tests are necessary to expand the data base for temperature suitability for native freshwater mussels; - Develop a method for conducting temperature tests with juvenile mussels and sediments. This task will utilize for guidance the recently approved standard method for conducting water-only toxicity tests with early life stages of freshwater mussels (ASTM 2006), but will standardize the sediment variables (e.g., particle size, organic content) that may influence temperature exposures. These tests will be conducted with juvenile mussels and are necessary to provide an accurate and precise test method. This task will address the issue of whether sediments may provide a partial thermal buffer for mussels in their native stream habitat; - Evaluate the relative sensitivity of juvenile native freshwater mussels to a range of common and extreme sediment temperatures (with and without overlying water) that may be encountered during summer periods in dewatered streams in the southeastern and central United States by conducting laboratory tests (using the method developed in Objective 2) with species that represent each of the two major subfamilies (Ambleminae and Unioninae) of mussels. These tests are necessary to expand the toxicity data base for temperature-based suitability for native freshwater mussels and will directly compare sediment temperature sensitivities to those already established in Objective 1 above and from our previous research (Pandolfo 2008) for water-only temperature sensitivities. This task will address the issue of whether sediments may provide a partial thermal buffer for mussels and ties directly to related research addressing instream habitat conditions for survival of mussels; - Sample common and imperiled mussel occurrences and associated microhabitat parameters, including temperature and flow, in one Atlantic Slope river basin to develop empirical models explaining mussel occurrence and abundance and field threshold values; - Synthesize all of the stream model and mussel temperature sensitivity, physiology, habitat, and community composition information for biologists and others involved with management of aquatic species and environmental quality.