Organic Carbon and Trace Element Cycling in a River-Dominated Tidal Coastal Wetland System (Tampa Bay, FL, USA)

Ryan P Moyer, Florida FWC, St Petersburg, FL, United States, Joseph M Smoak, University of South Florida Saint Petersburg, Saint Petersburg, FL, United States, Simon E Engelhart, University of Rhode Island, Department of Geosciences, Narragansett, RI, United States, Christina Powell, FL Fish & Wildlife Conservation Commission, Amanda R Chappel, FL Fish and Wildlife Conservation Commission, Fish and Wildlife Research Institute, St. Petersburg, FL, United States, Matthew J Gerlach, University of Rhode Island, Geosciences, Kingston, RI, United States, Andrew Kemp, Tufts University, Department of Earth and Ocean Sciences, Medford, United States and Joshua L Breithaupt, University of South Florida, College of Marine Science, St. Petersburg, FL, United States
Abstract:
Tampa Bay is the largest open water, river-fed estuary in Florida (USA), and is characterized by the presence of both mangrove and salt marsh ecosystems. Both coastal wetland systems, and small rivers such as the ones draining into Tampa Bay have historically been underestimated in terms of their role in the global carbon and elemental cycles. Climate change and sea-level rise (SLR) are major threats in Tampa Bay and stand to disrupt hydrologic cycles, compromising sediment accumulation and the rate of organic carbon (OC) burial. This study evaluates organic carbon content, sediment accumulation, and carbon burial rates in salt marsh and mangrove ecosystems, along with measurements of fluxes of dissolved OC (DOC) and trace elements in the water column of the Little Manatee River (LMR) in Tampa Bay. The characterization of OC and trace elements in tidal rivers and estuaries is critical for quantitatively constraining these systems in local-to-regional scale biogeochemical budgets, and provide insight into biogeochemical processes occurring with the estuary and adjacent tidal wetlands. Material fluxes of DOC and trace elements were tied to discharge irrespective of season, and the estuarine habitats removed 15-65% of DOC prior to export to Tampa Bay and the Gulf of Mexico. Thus, material is available for cycling and burial within marsh and mangrove peats, however, LMR mangrove peats have higher OC content and burial rates than adjacent salt marsh peats. Sedimentary accretion rates in LMR marshes are not currently keeping pace with SLR, thus furthering the rapid marsh-to-mangrove conversions that have been seen in Tampa Bay over the past half-century. Additionally, wetlands in Tampa Bay tend to have a lower rate of carbon burial than other Florida tidal wetlands, demonstrating their high sensitivity to climate change and SLR.
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