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USGS2025

Decision-support modeling and research priorities for establishing baseline conditions for outstandingly remarkable values, Obed Wild and Scenic River, Tennessee

The Obed River is the last undammed river in Tennessee. The Obed Wild and Scenic River is managed by the National Park Service and covers a protected area of the Obed River headwaters (including four contributing tributaries). The Obed Wild and Scenic River supports a unique ecosystem with eight federally listed species. The National Park Service is responsible for preserving the baseline free-flowing condition of the river and associated outstandingly remarkable values (ORVs). Previous studies have been mostly project-based with differing methods, thus complicating efforts to quantify long-term changes in environmental conditions. This report presents a science plan summarizing (1) ORV conditions, (2) recent results of a decision-support hydrologic model for OBRI, and (3) possible future research priorities. The decision-support model was created to model streamflow conditions and changes in the ORVs since park establishment in 1976 and during three additional time periods. Established baseline conditions could help with management of ORVs not dependent on streamflow.

Tennessee↗

USGS2025

Evaluation of the sensitivity of a federally endangered freshwater mussel (Venustaconcha trabalis) to selected chemicals

Protection of critically endangered species requires identification of factors limiting their survival and growth. Previous studies have demonstrated that unionid mussels are sensitive to some chemicals and the sensitivity was similar among different taxonomic families and tribes of mussels. However, common species of mussels were generally used in these previous studies; little is known about the sensitivity of endangered and threatened mussels relative to common species. The objective of this study was to evaluate the sensitivity of a critically endangered mussel (Tennessee bean, Venustaconcha trabalis ) to seven chemicals with different modes of toxic action (ammonia, chloride, nitrite, potassium, cobalt, manganese, nickel) in acute 96-h exposures and to three chemicals (nitrite, cobalt, iron) in chronic 28-d exposures conducted following standard methods. A commonly tested mussel (fatmucket, Lampsilis siliquoidea ) was also tested side-by-side with Tennessee bean in chronic exposures. Test chemicals were selected based on (1) chemicals of potential concern found in a review of existing data for the river where a population of Tennessee bean occurs or was historically present, (2) chemicals to which other mussels are sensitive, or (3) chemicals that had not been previously tested with mussels. Acute 50% effect concentrations (EC50s) for the seven chemicals from the Tennessee bean tests were within or close to the range of EC50s for other mussel species tested in previous studies, and chronic 20% effect concentrations for the three chemicals were similar between Tennessee bean and fatmucket, indicating the endangered species has sensitivity similar to other tested mussel species. Inclusion of the new mussel data in existing toxicity databases for freshwater organisms would rank one or more mussel species among the four most sensitive species to ammonia, chloride, potassium, and nickel in acute exposures and to nitrite, cobalt, and iron in chronic exposures.

Environmental Toxicology and Chemistry↗