Alkalinity Flux

This project will determine how marine sediments exposed to large riverine discharge affect ocean acidification from the increasing uptake of atmospheric carbon dioxide (CO2) in coastal waters. Although ocean acidification in coastal oceans affects marine life and commercial fisheries, little is known on the feedback from the underlying sediment on water column acidification processes. The role of large deposits from rivers in these processes has also never been investigated. The Mississippi River will be used as example of a river that plays an important economic role along the southern coast of the United States and provides a high sediment load to the nearby continental shelf in the Gulf of Mexico. The geochemical and microbiological processes responsible for the transformation of particles deposited on the seafloor will be characterized near the Mississippi River mouth and along the nearby continental slope. The release of acids (CO2) and bases (alkalinity) from the sediment will be quantified using autonomous instruments deployed on the seafloor to determine whether sediments contribute to the acidity of the surrounding water column or instead provide bases to buffer the water column from atmospheric CO2 inputs. As the Mississippi River discharge during the later Winter and Spring provides much more sediment to the coastal zone compared to the rest of the year, research cruises will be taken twice a year to determine how seasonal variations in riverine discharge affect the release of acids and bases into the water column.