Evaluating Methods for Estimating Seagrass Blue Carbon Stocks in Core Sound, North Carolina

Vegetated coastal environments (marshes, mangroves, and seagrass beds) perform a crucial ecosystem service by capturing carbon dioxide and storing it in the underlying sediment. Although there is a considerable body of literature on carbon stocks (g C m^-2) in seagrass beds, published values may misrepresent sequestration capacity. This is because the standard practice of measuring organic carbon in the top 10-30 cm of sediment and extrapolating to a meter assumes that carbon content is constant at depth. Using five sediment cores from seagrass meadows in Core Sound, North Carolina, we evaluated the assumption that carbon content is constant at depth by developing facies models for the seagrass depositional environment, characterizing organic carbon composition to the base of each seagrass unit, and comparing measured stocks of the whole seagrass unit with extrapolated stocks from surface samples. Using these methods, we found that North Carolina’s seagrass beds form three facies successions (continuous, stacked, and sand-capped), contributing to site-specific variability in down core carbon content. Where seagrass exists at the surface, our cores show extrapolating can overestimate a seagrass unit’s total carbon stock by as much as 297%. These findings are significant because they suggest that in order to perform accurate seagrass carbon budgeting, the blue carbon community must collect longer cores and analyze the entire seagrass depositional unit.

Presentation Preference: Poster

Primary Presenter: Lillian Cooper, University of North Carolina at Chapel Hill (lilymc@live.unc.edu)

Authors:

Lillian Cooper, University of North Carolina at Chapel Hill  (lilymc@live.unc.edu)

Yasamin Sharifi, University of North Carolina at Chapel Hill  (yasamin@email.unc.edu)

Antonio Rodriguez, University of North Carolina at Chapel Hill  (abrodrig@email.unc.edu)