Methane Dynamics in two South Florida Mangrove Estuaries: Water-Air Fluxes and Export to the Coastal Ocean

Mangroves and other coastal wetland ecosystems are among the most carbon-rich ecosystems in the world (Donato et al., 2011). An important uncertainty in the carbon balances of these systems is the lateral transport of methane (CH₄), an important greenhouse gas, from the pore waters of vegetated zones to the estuarine water column and subsequent flux to the atmosphere and/or transport to the coastal ocean. In this study we report longitudinal distributions of dissolved CH₄ in two rivers of a mangrove-dominated estuary in South Florida over five consecutive days, and determine air-water fluxes of CH₄, and CH₄ export to the coastal ocean.

Mean near-surface CH₄ concentrations in the Shark and Harney Rivers were 110±52 and 167±45 nM, respectively, and the CH₄ source was a combination of lateral mangrove inputs and export from upstream freshwater wetlands. Integrated air-water CH₄ fluxes from the Shark and Harney were determined to be 9.24±0.7 and 14.0±1.0 µmol m^-2 h^-1, respectively. Methane fluxes to the atmosphere and the coastal ocean will be discussed within the context of the overall carbon budget of the coastal Everglades mangrove ecosystem.

References

D.C. Donato et al., (2011). Mangroves among the most carbon-rich forests in the tropics. Nature Geoscience 4, 293-297.