Regional Conditions Factors such as geography, climate, and human activities vary across different regions, impacting the extent and rate of ocean acidification. Mid-Atlantic Coastal Ecosystems The Mid-Atlantic coastal region is characterized by low-salinity waters influenced by the Labrador Coastal Current flowing south and saline Gulf Stream-influenced water flowing north. This region includes several estuarine systems, including two major bays, the Chesapeake and the Delaware. How Regional Conditions Influence Saturation State Many marine organisms, including shellfish, mollusks and plankton, make calcium carbonate skeletal structures in the form of aragonite or calcite. The saturation state of calcium carbonate is a measure of whether the skeletal structures will dissolve (low saturation state) or form (high saturation state). Seasonal Changes 1 In winter, saturation state is suppressed throughout the region due to cooling of the water, and the respiration or remineralization of the algal material that is produced during the spring and summer seasons. The combination of these processes elevate CO2 and decrease pH. This natural seasonality complicates assessments of changes due to anthropogenic acidification and highlights the need for sustained monitoring of regional ocean chemistry. Research Needs 1 Saturation state and the ability of an organism to form based on calcium carbonate concentrations is only one way that acidification impacts ocean species. Research shows higher levels of acidification can impact the fertilization rates and consumption rates of fish species. More research is being conducted and is needed to understand the full spectrum of impacts acidification may have on the Mid-Atlantic’s marine organisms and ecosystems. References Saba, G. K., Goldsmith, K. A., Cooley, S. R., Grosse, D., Meseck, S. L., Miller, A. W., Phelan, B., Poach, M., Rheault, R., St.Laurent, K., Testa, J. M., Weis, J. S., & Zimmerman, R. (2019). Recommended priorities for research on ecological impacts of ocean and coastal acidification in the U.S. Mid-Atlantic. Estuarine, Coastal and Shelf Science, 225, 106188. https://doi.org/10.1016/j.ecss.2019.04.022 Wang, Z. A., Wanninkhof, R., Cai, W.-J., Byrne, R. H., Hu, X., Peng, T.-H., & Huang, W.-J. (2013). The marine inorganic carbon system along the Gulf of Mexico and Atlantic coasts of the United States: Insights from a transregional coastal carbon study. Limnology and Oceanography, 58(1), 325–342. https://doi.org/10.4319/lo.2013.58.1.0325 Wanninkhof, R., Barbero, L., Byrne, R., Cai, W.-J., Huang, W.-J., Zhang, J.-Z., Baringer, M., & Langdon, C. (2015). Ocean acidification along the Gulf Coast and East Coast of the USA. Continental Shelf Research, 98, 54–71. https://doi.org/10.1016/j.csr.2015.02.008 3