Preprints
https://doi.org/10.5194/egusphere-2022-525
https://doi.org/10.5194/egusphere-2022-525
 
13 Jul 2022
13 Jul 2022
Status: this preprint is open for discussion.

Air-sea gas exchange in a seagrass ecosystem

Ryo Dobashi and David T. Ho Ryo Dobashi and David T. Ho
  • Department of Oceanography, University of Hawai‘i at Mānoa, 1000 Pope Road, Honolulu, Hawaii 96822, USA

Abstract. Seagrass meadows are one of the most productive ecosystems in the world and could play a role in mitigating the increase of atmospheric CO2 from human activities. Understanding their role in the global carbon cycle requires knowledge of air-sea CO2 fluxes and hence knowledge of the gas transfer velocity. In this study, gas transfer velocity and its controlling processes were examined in a seagrass ecosystem in south Florida. Gas transfer velocity was determined using the 3He and SF6 dual tracer technique in Florida Bay near Bob Allen Keys (25.02663° N, 80.68137° W) between 3 and 8 April 2015. The observed gas transfer velocity normalized for CO2 in freshwater at 20 °C, k(600), was 4.8 ± 1.8 cm h-1. The result gas transfer velocities were lower than previous experiments in the coastal and open oceans at the same wind speeds. Therefore, using published wind speed/gas exchange parameterizations would overpredict gas transfer velocities and CO2 fluxes in this area. The deviation in k(600) from other settings was weakly correlated to tidal motion and air-sea temperature difference, implying that wind is the dominant factor driving gas exchange. The lower gas transfer velocity was most likely due to wave attenuation by seagrass and limited wind fetch in this area. A new wind speed/gas exchange parameterization is proposed (k(600)=0.125u102), which might be applicable to other seagrass ecosystems and wind fetch limited environments.

Ryo Dobashi and David T. Ho

Status: open (until 08 Sep 2022)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on egusphere-2022-525', Anonymous Referee #1, 15 Aug 2022 reply

Ryo Dobashi and David T. Ho

Data sets

Tracer_release_experiment_Florida_bay Ryo Dobashi https://doi.org/10.5281/zenodo.6730934

Ryo Dobashi and David T. Ho

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Short summary
Seagrass meadows are productive ecosystems and bury much carbon. Understanding their role in the global carbon cycle requires knowledge of air-sea CO2 fluxes and hence the knowledge of gas transfer velocity (k). In this study, k was determined from the dual tracer technique in Florida Bay. The observed gas transfer velocity was lower than previous studies in the coastal and open oceans at the same wind speeds, most likely due to wave attenuation by seagrass and limited wind fetch in this area.