Zimmerman (CMS 2023): Prototype for a Blue Carbon Observatory: Submerged Aquatic Vegetation in the Chesapeake Bay - Where's the Peat?
Richard Zimmerman, Old Dominion University, rzimmerm@odu.edu (Presenter)
Victoria Hill, Old Dominion University, vhill@odu.edu
David Burdige, Old Dominion University, dburdige@odu.edu
Richard Hale, Old Dominion University, rphale@odu.edu
We are using high-resolution satellite imagery from Planet Labs to quantify the distribution and abundance of submerged aquatic vegetation (SAV) across the Chesapeake Bay. These data are being linked to spatial patterns of SAV productivity and Blue Carbon accumulation along the Bay’s strong salinity gradient—from the freshwater wild celery meadows of the Susquehanna Flats to the dense eelgrass beds in the oceanic coastal lagoons of the Delmarva Peninsula. Organic carbon preservation is expected to be highest in freshwater sediments and to decline with increasing salinity, as microbial dissimilatory sulfate reduction becomes more active. However, pyrite formation and carbon trapping via the shallow water alkalinity pump are likely to increase in importance downstream since sulfate is ~250 times more abundant in seawater than in freshwater. Satellite data reveal pronounced seasonal cycles in tidal freshwater SAV biomass and carbon, with strong summer growth and winter die-back. In contrast, SAV in polyhaline and marine zones shows more temporal stability, despite frequent leaf turnover. Annual above-ground carbon productivity is estimated at ~100 g C per m^2 per yr for both systems, but the fate of this biomass remains uncertain. Porewater alkalinity correlates positively with salinity and increases in concentration up to threefold within the top 10 cm of sediment, with the benthic flux of this alkalinity representing a previously underappreciated mechanism for transferring atmospheric CO2 into stable dissolved inorganic carbon in the ocean, comparable in scale to SAV productivity. Analyses of sediment cores are ongoing; we expect pyrite levels to track alkalinity trends, while particulate organic carbon (POC) may show the opposite pattern. Although permanent POC burial may decline in marine sediments, the shallow water alkalinity pump appears to significantly enhance the carbon sequestration capacity of SAV, especially in high-salinity environments.
Associated Project(s):
Poster Location ID: 2
Presentation Type: Poster
Theme: Aquatic Biomass