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

North Carolina Project

Advancing the knowledge of freshwater mussel conservation: examining the role of manganese on recent mussel die-offs and enigmatic declines

August 2020 - May 2023


Participating Agencies

  • Science Support Partnership Program

The Southeastern and Mid-Atlantic regions of the United States contain the greatest biodiversity of native freshwater mussels in the world, but they are highly imperiled due to habitat alteration and destruction, pollution and poor water quality, and the introduction of aquatic invasive species. Over recent decades, U.S. Fish and Wildlife Service and state fish and wildlife management agency biologists have responded to an increased frequency of mussel die-offs, enigmatic declines, and problems with decreased mussel growth and survival, but a definiticve cause has yet to be identified. However, a recent, but unexplained relation has been identified between manganese (Mn) concentrations and several of these mussel decline and die-off events. Therefore, we propose to examine the toxicity of Mn to mussels in controlled laboratory tests with captively propagated larval and juvenile mussels and with adult mussels collected from low Mn-containing streams. We will then compare these findings to mussels and Mn concentrations in water and sediment from streams where die-offs and declines have occurred. This high impact project focuses on native freshwater mussel conservation priorities of the Southeast region and potentially nation-wide. The project has direct links to the strategic science needs of the natural and cultural resource managers in the region and beyond, because it addresses specific priorities outlined in the State Wildlife Action Plans for the conservation of native freshwater mussels in the States of North Carolina and Virginia and federal at-risk molluscan species in Region 4 and Region 5 of the USFWS and others across the country. In addition, this project will have direct relevance and benefit to other federal resource management and research agencies, such as the U.S. Environmental Protection Agency, who utilize the mussel toxicity data in water quality criterion development. The completion of these research objectives will provide natural resource managers and other decision makers with real-world exposure and survival scenarios and would directly impact the recovery plan for the endangered Appalachian Elktoe mussel by informing the potential causal mechanisms for its die-off and decline in the Little Tennessee River of North Carolina. The persistence of all freshwater mussels will be addressed in the scope of the project.