Long-Term Carbon Burial in Marshes of the Mississippi River Delta

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Wetlands along the Gulf of Mexico coast play an important role in the global carbon cycle, but as they  rapidly convert to open water, their potential for carbon storage is declining. USGS is working to provide accurate, long-term marsh soil carbon sequestration rates. 

Coastal marsh, Mississippi River Delta Plain
Coastal marsh, Mississippi River Delta Plain

The Science Issue and Relevance: Wetlands play an important role in the global carbon cycle. These productive landscapes are highly efficient at accumulating soil organic matter and can function as important carbon sinks. Wetlands have been estimated to account for over thirty percent of the world’s soil organic carbon stock even though they account for less than 10% of the earth’s land surface area.  Although over half of all coastal wetlands in the United States are located along the northern Gulf of Mexico, these wetlands are converting to open water at an alarming rate and, as such, the potential for carbon storage is declining. In recent years, interest in carbon sequestration as an ecosystem service has increased substantially as regulatory agencies examine the feasibility of integrating carbon credits into their ecosystem restoration and management plans. This study aims to provide accurate, long-term marsh soil carbon sequestration rates based on 210 Pb analysis and direct measurement of carbon content across the Mississippi River delta plain.

Methodology for Addressing the Issue: In 2008 and 2013, a total of 27 marsh cores were collected across Breton Sound basin. In early 2016, 25 additional cores will be collected in Barataria basin. Each core, 10 cm in diameter and 50 cm in length, will be sectioned into 2-cm sections. Core sections will be analyzed for 210 Pb activity, bulk density, loss-on-ignition, and total carbon. Carbon inventories will be determined for each core, and carbon sequestration rates will be determined by dividing the mass of the carbon inventory by the age of the bottom core section.  

Map of Location of Study: Mississippi River Delta Plain
Map of Location of Study: Mississippi River Delta Plain

Future Steps: After carbon sequestration rates are quantified for the Mississippi River delta plain, collaborators across the Gulf of Mexico will be solicited and a paper synthesizing long-term burial rates across the Gulf will be initiated. 

Location of Study:  Mississippi River Delta Plain (29.5804°N, 89.8343°W)