B056-04
Long term fate of carbon stock soil profiles in rapidly eroding coastal wetlands

Thursday, 10 December 2020: 17:42
Virtual
Yadav Sapkota, Louisiana State University, Baton Rouge, LA, United States, John R White, Louisiana State University, Oceanography & Coastal Sciences, Baton Rouge, LA, United States, Z. George Xue, Louisiana State University, Oceanography and Coastal Sciences, Baton Rouge, LA, United States, Robert L Cook, Louisiana State University, Chemistry, Baton Rouge, LA, United States and Lisa G Chambers, University of Central Florida, Orlando, FL, United States
Recorded Presentation
Abstract:
Marsh edge erosion is one of the major causes of land loss in wetland dominated coastlines. The edge erosion transports the previously-stored organic carbon and associated nutrients into the adjacent estuary. Upon exposure to the oxygenated water of the estuary, the mineralization of exported organic matter may increase. Assessing soil carbon stocks and understanding the fate of eroding carbon is an essential component of the wetland carbon budget. The objective of this study was to measure the marsh edge erosion rate and understand the fate of the eroding carbon through biogeochemical analyses. The erosion rate was monitored along 33 transects for up to four years in Barataria Basin, Louisiana. Eleven soil cores (~2m deep) were collected from four highly eroding sites. Cores were sectioned in to 10 cm intervals and analyzed for total, labile and refractory carbon, carbon density, select enzyme and microbial activities, and organic and inorganic phosphorus forms. Marshes in Barataria Basin are experiencing edge erosion at the rate of 1.42 ± 0.2 m yr-1. The total C, labile C, and carbon density increased with depth at all sites. The carbon density at 1-1.5 m deep (0.04 ±0.003 g cm-3) was significantly higher (p<0.001) than the top 1 m soil (0.032±0.002 g cm-3), indicating the need for considering deeper carbon profile for blue carbon stock assessment. The age of the intact peat exposed on the surface of the adjacent estuarine bottom was 458±84 yBP indicating recently eroded wetland carbon is not buried in the estuary. Significant anaerobic microbial activity was present at all the soil depths suggesting a high potential of mineralization of eroded carbon in the aerobic estuarine water which may contribute to the atmospheric CO2 pool. These findings help to inform coastlines experiencing high relative sea level rise at present or coastlines that are projecting high sea level rise in the near future that they are susceptible to losing an enormous amount of previously sequestered carbon over a relatively short period. Efforts should be made to preserve these vast carbon stocks from erosion, preventing release to the atmosphere.
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