Vegetated coastal ecosystems, including seagrass meadows, were proposed as globally significant sites for carbon (C) sequestration, because of their potential to accumulate organic carbon (OC)-rich sediments. However, many seagrass meadows are found in tropical to subtropical latitudes, where sediment formation can be dominated by carbonates (IC). The CO₂ production resulting from IC formation (dissolution) within seagrass meadows may offset (enhance) their potential as C sinks. Here, we examine OC and IC burial fluxes of South Florida seagrass meadows using 18 ²¹⁰Pb-dated sediment cores spanning a range of geomorphic settings from estuarine to backreef environments. We find considerable variability in sediment C stocks across the seascape, with spatial decoupling of C stocks and C burial rate hotspots. Through analysis of C stable isotopes and other auxiliary data, we estimate the proportion of autochthonous OC and IC production and derive first-order estimates of net benthic C fluxes. We find that particularly meadows in Florida Bay are likely net C sources to the atmosphere, supporting recent findings from eddy covariance measurements. We go on to evaluate the relative importance of seagrass condition versus seascape configuration for benthic OC, IC, and net C burial fluxes, adding to the conceptual framework for blue carbon potential in carbonate-dominated seagrass meadows.

Primary Presenter: Johannes Krause, Florida International University (jkrause@fiu.edu)

Authors:

Johannes Krause, Florida International University  (jkrause@fiu.edu)

Ariane Arias Ortiz, Autonomous University of Barcelona  (ariane.arias@uab.cat)

James Fourqurean, Florida International University  (fourqure@fiu.edu)