Importance of Groundwater to Dissolved Organic Carbon Export from a Florida Salt Marsh to the Gulf of Mexico

Dissolved organic carbon (DOC) export from salt marshes via groundwater represents an important source to the coastal ocean. Coastal aquifers and salt marshes are especially vulnerable to rising sea levels due to their low elevation and proximity to the ocean. Carbon sequestration in marshes will become overwhelmed by inundation and increase carbon release from these organic-rich ecosystems. Groundwater flushing through sediments mixes with tidal recharge, and the resulting submarine discharge enhances DOC export in this Florida salt marsh study, where the groundwater DOC export is derived from a regional water balance and total surface water DOC export. Fresh groundwater discharge from the Econfina-Aucilla salt marsh is 0.072-0.14 cm/day. The seasonal groundwater DOC export to the Gulf of Mexico is 150-180 gC/m2/year, or 2.2 to 34% of the total carbon exported from the marsh. Clearly, groundwater discharge from salt marshes is an important source to the global ocean carbon cycle.