Paper No. 19-3
Presentation Time: 1:30 PM-5:30 PM
SOURCES OF BLUE CARBON IN NATURAL AND RESTORED MANGROVE ECOSYSTEMS OF BISCAYNE BAY, FLORIDA, USA
ROSENBERG, Brittany1, MYERS, Braden1, KU, Timothy1, HERNANDEZ, Shay2, MARTINI, Anna2, MAIN, Roxanne2, RUDERMAN, Ethan2 and THORHAUG, Anitra3, (1)Department of Earth and Environmental Sciences, Wesleyan University, 265 Church Street, 455 Exley Science Tower, Middletown, CT 06459, (2)Geology Department, Amherst College, 11 Barrett Hill Rd, Amherst, MA 01002, (3)Greater Caribbean Energy and Environmental Foundation, 1359 SW 22 Terrace, Miami, FL 33145
Atmospheric carbon dioxide concentrations have significantly increased since the 18
th century contributing to a worsening climate crisis. Therefore, carbon removal from the atmosphere is critical in climate change mitigation strategies. Blue Carbon Environments (BCEs), such as mangrove forests and seagrass beds, are high organic carbon sequestration sites that are becoming increasingly important in climate policies. However, many factors remain poorly determined despite greater attention to natural and restored BCEs. For example, sediment carbon buried beneath mangrove stands is generally considered to originate from the above mangroves, but this carbon may be derived from multiple sources. This study aims to quantify the sediment organic carbon sources in natural and restored mangrove forests in Biscayne Bay, Florida.
In the summer of 2022, vegetation (mangrove, seagrass, and plankton) samples and sediment cores were collected in mangrove forests from a natural site (near Matheson Hammock State Park) and a site restored in the 1990s (near Bill Baggs State Park). Samples were analyzed for organic C and CaCO3 concentrations, C/N, and d13C-organic C. We developed a three-end-member mixing model to calculate the fraction of sediment organic carbon attributed to mangrove, seagrass, and plankton sources. Changes in sediment calcium carbonate concentrations from 0 to 50% demonstrate shifts in sediment sources and mark the onset of estuarine or marine conditions at the restored site. Sediment carbon geochemistries at the natural site show a general increase of seagrass and plankton sources in recent times, punctuated with increased mangrove carbon burial episodes. Overall, mangrove organic matter comprises a more significant proportion of the buried organic matter in the restored site compared to the natural location. Our results highlight the importance of different organic carbon sources to blue carbon accounting in coastal environments.
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