Ocean acidification more rapid in coastal oceans

New research under the joint NCCOS Competitive Research Program and NOAA Ocean Acidification Program finds the combined effects of anthropogenic and biological carbon dioxide (CO2) inputs may lead to more rapid acidification in Chesapeake Bay and other coastal water compared to the open ocean. The results indicate that eutrophication can exacerbate ocean acidification (OA) where animal and plant respiration contributes a far greater acidification in the coastal oceans relative to the open ocean.

The study, led by Dr. Wei-Jun Cai of the University of Delaware, is part of a NCCOS-sponsored project team studying interactions between OA and eutrophication in estuaries. “The study shows for the first time that the oxidation of hydrogen sulfide and ammonia from the bottom waters could be a major contributor to lower pH in coastal oceans and may lead to more rapid acidification in coastal waters compared to the open ocean” says Dr. Cai, in the online University of Delaware’s UDaily. Increased acidification can dissolve the calcium carbonate in the shells of valuable clams, oysters, and certain plankton and lead to poor acid buffering capacity of the water.

Coastal eutrophication occurs with increased inputs of nutrients that fuel large algal blooms. Decomposition of algal organic matter from highly productive surface waters leads to the development of seasonally low oxygen (hypoxic) or even zero oxygen (anoxic) bottom waters in many coastal water bodies, including Chesapeake Bay. Little or no oxygen generates chemical processes that decrease oxygen, release acidic hydrogen sulfide and CO2 from bottom sediments (called oxidation-reduction or “redox” chemistry) and a lowering the pH (i.e., increasing acidity). Acidic compounds in the atmosphere (e.g., sulfur and nitrogen oxides) also dissolve in surface waters leading to acidification. The coupling between redox and acid–base chemistry has not been explored extensively in seasonally anoxic and partially mixed estuaries nor in permanently anoxic deep basins.

Citation:  Cai, Wei-Jun Cai, Wei-Jen Huang, George W. Luther III, Denis Pierrot, Ming Li, Jeremy Testa, Ming Xue, Andrew Joesoef, Roger Mann, Jean Brodeur, Yuan-Yuan Xu, Baoshan Chen, Najid Hussain,George G. Waldbusser, Jeffrey Cornwell, and W. Michael Kemp. 2017. Redox reactions and weak buffering capacity lead to acidification in the Chesapeake Bay. Nature Communications 8 (369): 1-12. doi: 10.1038/s41467-017-00417-7

Media: Roberts, Karen B. Keeping an Eye on Ocean Acidification in Chesapeake Bay. UDaily, August 29, 2017.

For more information, contact Elizabeth.Turner(at)noaa.gov.

NOAA News, 21 September 2017. Article.

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