Black to Blue: Quantifying Recalcitrant and Labile Carbon Stocks in a DE Tidal Wetland

Calyn Crawford, National Oceanic and Atmospheric Administration, Simpsonville, South Carolina, United States and Kari A St.Laurent, Delaware National Estuarine Research Reserve, Delaware Department of Natural Resources and Environmental Control, Dover, United States
Coastal wetlands play an important role in the global carbon budget due to their ability to sequester and store carbon as sediment organic matter. This sequestered carbon is termed “blue carbon” and helps maintain and mitigate input of anthropogenic inorganic carbon into the atmosphere. However, carbon pools are complex and past research has not quantified the percentage of blue carbon that is more recalcitrant, termed black carbon, an incompletely combusted form of organic matter. When deposited within sediments, black carbon can be more stable than other labile organic matter, pull organic pollutants from the surrounding soil and have a longer storage potential. Thus, this project investigated the ratio of black to blue carbon existing in the St. Jones Reserve tidal marsh in Dover, DE. This study is the first of its kind to include quantitative black carbon and blue carbon measurements for a Delaware wetland. The ratio of carbon was analyzed in addition to dry bulk density, carbonate, and an elemental analysis. Data were collected using sediment cores within the root zone (~30 cm) and analyzed for organic matter using loss on ignition (blue carbon) and chemothermal oxidation (black organic matter) analyses. Preliminary results suggest black organic matter makes up between 0.00-17.84% of the organic matter while labile organic matter composes between 8.47-42.09% of the sediment. Additionally, percent organic matter values fall between 8.33-49.14%. A subset of samples will additionally be analyzed for organic and black carbon using CHNS elemental analysis. This data has not been received in full and will be analyzed once all data has been submitted for data processing. This study will provide a better understanding of carbon sequestration and spatial patterns of blue and black carbon concentrations in a tidal marsh.