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NCCOS Project

Modeling Ocean Acidification in the Coastal Zone

This project began in January 2013 and is Ongoing

Adding carbon dioxide (CO2) to seawater raises the acidity of seawater, which can adversely affect marine life and fisheries. Coastal waters receive both atmospheric CO2 and CO2 from water pollution, and their combination can disproportionately accelerate acidification. This interaction is highly dependent on salinity and temperature. We created a model that evaluates all of these parameters and reports the expected acidification, allowing coastal managers to predict outcomes in their regions.

Why We Care
Ocean acidification is an emerging global problem that threatens fisheries and related food webs. Studies have shown that a more acidic environment can interfere with the shell and skeleton development of calcifying species such as oysters, clams, sea urchins, corals, and calcareous plankton. When shelled organisms are at risk, food webs and fishery-dependent economies may also be at risk. With the pace of ocean acidification accelerating, there is a need to strengthen our understanding of acidification processes to better inform decision making and action.

What We Are Doing 
Ocean acidification research is largely concentrated on the open ocean, despite the fact that most of the ocean’s productivity responsible for supporting key fisheries is found in the coastal zone. In response to this data gap, we focused our attention on acidification in coastal and near-shore waters. Specifically, we examined how water acidification is affected by increases in atmospheric CO2 and CO2 released from the breakdown of organic matter, over a range of salinities and temperatures. We used acidity data from the northern Gulf of Mexico and the Baltic Sea to verify our model predictions.

The project team included partners from NOAA/NCCOS and the University of Georgia.

What We Found and Benefits of our Work 
Our model showed that the two CO2 acidification processes often interact synergistically—such that the resulting effect on pH (a measure of acidification) is more than additive—and that these interactions are highly dependent on seawater salinity and temperature. The model could be converted to an operational forecast to help coastal managers predict and plan for ocean acidification in their regions.

This study showed that ocean acidification research and mitigation efforts should also address biological inputs of CO2 linked to coastal eutrophication and nutrient pollution, in addition to the current focus on increasing atmospheric CO2 linked to the burning of fossil fuels.

Additional Resources

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Peer-Reviewed Publications

  • Sunda, W.G. and W. Cai. 2012. Eutrophication induced CO2-acidification of subsurface coastal waters: interactive effects of temperature, salinity, and atmospheric PCO2. Environmental Science and Technology. 46(19):10651–10659.

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