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Estuaries play an outsized role in the global carbon budget

The sources and sinks of carbon in the coastal ocean are important, but little understood, components of the global carbon budget (Cai 2011). Hopkinson et al. (2012) reviewed available information on the amount of C stored in coastal vegetated wetlands (marshes, mangroves, and sea grass beds). Areal rates of C burial in these systems are extremely high and they are important C sinks on a global scale. They warn that sea level rise and coastal armoring coupled with a rise in global temperature will all result in decreased C storage in these systems. Jiang et al. (2013) evaluated C export to the South Atlantic Bight. They found that terrestrially-derived CO2 from both rivers and intertidal marshes was exported to the continental shelf, with highest inputs closest to shore (Fig.). This past year, GCE investigators published a major review paper on the coastal ocean in Nature (Bauer et al. 2013) that attests to the extremely high level of metabolism of wetland-dominated estuarine systems in the global ocean and the overall importance of organic C burial in wetland sediments. This blue carbon burial represents a significant portion of the net air-sea flux of CO2 to the coastal ocean. Although there is still much uncertainty in global estimates, they suggest that intertidal wetlands also act as a net source of C to estuaries, which then export both organic and inorganic C to continental shelves. They point out that changes in river discharge, the loss of coastal wetlands, and increasing atmospheric levels of CO2 will all alter shelf-atmosphere-open ocean C exchange in the future.

Plant-Herbivore interactions

Spatial distributions of ΔpCO2 inputs (referenced to 23.11C) from rivers (left), marshes (middle) and shelf (right) during January (top) and May (bottom). From Jiang et al. (2013).

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This material is based upon work supported by the National Science Foundation under grants OCE-9982133, OCE-0620959, OCE-1237140 and OCE-1832178. Any opinions, findings, conclusions, or recommendations expressed in the material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation.