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).

Offshore vs. Nearshore Conditions

Acidification works to decrease saturation state. The nearshore waters of the Mid-Atlantic exhibit relatively low aragonite saturation states (blue regions on the map), while further offshore the warmer, more saline and more strongly buffered waters have relatively higher saturation states (orange and red on the map). As freshwater flows from Mid-Atlantic estuaries into nearshore regions, excess nutrients from fertilizer, wastewater treatment, and stormwater runoff lead to coastal eutrophication and exacerbate acidification.

Visit The Mid-Atlantic Ocean Data Portal for Regional Monitoring Maps

The above map depicts the aragonite saturation in the Mid-Atlantic. Low saturation state will result in the dissolution the shells or skeletal structures of many marine organisms, while high saturation states will allow shells to form.

Seasonal Changes

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

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

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