EGU General Assembly 2020
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

Alkalinity and CO2 fluxes in a tropical seagrass meadow

Bryce Van Dam1, James Fourqurean2, and Ashley Smyth3
Bryce Van Dam et al.
  • 1Helmholtz-Zentrum Geesthacht, Institute of Coastal Research, Germany (
  • 2Biological Sciences, Institute of Environment, Florida International University
  • 3Tropical Research and Education Center, University of Florida

Total alkalinity (TA) production in vegetated coastal systems is considered a putative sink for atmospheric CO2, due to the increase in the seawater buffer capacity when TA is produced in excess of DIC. Much of the TA generated in these habitats is derived from the reduction of NO3 and Fe, but in oligotrophic tropical waters dominated by carbonate sediments, these sources of TA may be minimal. To address this uncertainty, we measured a suite of sediment-water fluxes (SO4, N2, TA, DIC, DOC, etc) in a tropical and calcifying seagrass meadow, allowing us to identify the biogeochemical processes responsible for TA generation and consumption. We placed this information into the context of water-air CO2 exchange, which was measured by atmospheric eddy covariance. Net N2 fluxes indicated that denitrification was a negligible TA source in this oligotrophic seagrass meadow, which at times was net N2-fixing. Instead, sediment-water TA fluxes were dominated by the balance between SO2 reduction, H2S oxidation, and carbonate dissolution/precipitation. Air-water CO2 exchange was small and variable, reflecting the highly-buffered seawater chemistry and oligotrophic nature of this seagrass meadow.

How to cite: Van Dam, B., Fourqurean, J., and Smyth, A.: Alkalinity and CO2 fluxes in a tropical seagrass meadow, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-2861,, 2020

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