Final Report: Impacts of Sea Level Rise on At-risk Native Freshwater Mussels in Atlantic Coastal Rivers
Dates
Publication Date
2023-11-14
Citation
Gregory Cope, 2023-11-14, Final Report: Impacts of Sea Level Rise on At-risk Native Freshwater Mussels in Atlantic Coastal Rivers: U.S. Geological Survey.
Summary
Sea levels across the planet are rising, and particularly, along the eastern coast of the United States. Climate-induced sea level rise can result in the inundation and intrusion of seawater into freshwater drainages. This would alter salinity regimes and lead to the salinization of coastal freshwater ecosystems. Increased salinity levels in freshwater can negatively affect freshwater dependent species, including native mussels belonging to the order Unionida, which are highly sensitive to changes in water quality. Sea salt is largely made up of sodium (Na+) and chloride (Cl-) ions, forming sodium chloride (NaCl), a known toxicant to freshwater mussels. However, sea salt is a mixture that also contains other major ions, including potassium [...]
Summary
Sea levels across the planet are rising, and particularly, along the eastern coast of the United States. Climate-induced sea level rise can result in the inundation and intrusion of seawater into freshwater drainages. This would alter salinity regimes and lead to the salinization of coastal freshwater ecosystems. Increased salinity levels in freshwater can negatively affect freshwater dependent species, including native mussels belonging to the order Unionida, which are highly sensitive to changes in water quality. Sea salt is largely made up of sodium (Na+) and chloride (Cl-) ions, forming sodium chloride (NaCl), a known toxicant to freshwater mussels. However, sea salt is a mixture that also contains other major ions, including potassium (K+), sulfate (SO4--), calcium (Ca++), strontium (Sr++), and magnesium (Mg++) among others. Freshwater mussels exposed to sea salt would be exposed to each of the sea salt ions at the same time, resulting in a mixture toxicity effect. The mixture toxicity of these ions on early life stages of freshwater mussels is largely unknown because most research to date has evaluated individual salt ions in relative isolation. Therefore, we conducted acute toxicity tests on early life stages (glochidia (larvae) and juveniles) of three freshwater mussel species that inhabit Atlantic Slope drainages (non-salinity adapted Atlanticoncha ochracea, salinity adapted Atlanticoncha ochracea, Sagittunio nasutus, and Utterbackiana implicata). Glochidia and juveniles of each species were exposed to a control and 6 concentrations of Instant OceanĀ® Sea Salt (IOSS), a synthetic sea salt that closely resembles the ionic composition of natural sea salt. Exposure concentrations were 1 part(s) per thousand (ppt), 2 ppt, 8.5 ppt, 12.5 ppt, 17 ppt, and 34 ppt. We calculated the median effective concentration (EC50) for each of the 8 acute toxicity tests and found that glochidia were more sensitive than juveniles to IOSS. EC50s at hour 24 for the glochidia ranged from 0.38-3.6 ppt, with the most sensitive freshwater mussel being the non-salinity adapted Atlanticoncha ochracea, exhibiting an EC50 of 0.38 ppt (95% C.I. = 0.33-0.44). Juvenile freshwater mussels exhibited EC50s at hour 96 ranging from 5.0-10.4 ppt, with the least sensitive freshwater mussel being the non-salinity adapted Atlanticoncha ochracea, exhibiting an EC50 of 10.4 ppt (95% C.I. = 9.1-12.0). Our results show that acute exposure to sea salt adversely affects freshwater mussel viability, particularly glochidia. This information can be used by natural resource managers and to enhance freshwater mussel conservation strategies in regions that are, or will be impacted by climate-induced sea level rise and associated freshwater salinization.