Regional Conditions

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.


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). Acidification works to decrease saturation state. The nearshore waters of the Mid-Atlantic exhibit relatively low aragonite saturation states (indicated by the blue regions on the map below), while further offshore the warmer, more saline and more strongly buffered waters have relatively higher saturations states (orange and red areas on the map). Freshwater input from the Mid-Atlantic estuaries carries excess nutrients (partly as a result of pollution from fertilizer, wastewater treatment, and stormwater runoff), which lead to coastal eutrophication and exacerbate acidification in the nearshore regions.

(The above map depicts the aragonite saturation in the Mid-Atlantic. Aragonite is a critical form of calcium carbonate that many marine organisms require to develop. Low saturation state will result in the dissolution of many marine organisms, while high saturations stats will result in the formation of marine organisms.)


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.  


While the focus here is on the regional conditions of saturation state in the Mid-Atlantic, 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 consumptions rates of fish species. More research is being conducted and is needed to understand the full spectrum of impacts acidification may have on marine organisms.


Wang et al., 2013. Limnol. Oceanogr. 58, 325-342, doi:10.4319/lo.2013.58.1.0325

Wanninkhof et al., 2015, Continental Shelf Res., 98, 54-71, doi:10.1016/j.csr.2015.02.008