Determining effect of seagrass-mediated CO flux on the atmospheric cooling potential of a subtropical intertidal seagrass meadow.

Atmospheric greenhouse gas (GHG) emissions from seagrass meadows that determine the ecosystem atmospheric cooling effect have rarely been quantified. This study measured the simultaneous fluxes direct to the atmosphere of three GHGs (CO, CH and NO) within a Halophila beccarii seagrass meadow and an adjacent unvegetated bare intertidal flat, and their relationships to seagrass abundance and relevant soil parameters. The results showed that seasonal variation in seagrass abundance was strongly linked with the CO exchange rate. The CH and NO fluxes were similarly low at both sites and comparable between winter and summer. The global warming potential of CH and NO reduced the ecosystem CO uptake by only 5 % at the seagrass site. The results indicated that the H. beccarii meadow had a stronger atmospheric cooling effect than the bare flat and that the seagrass-mediated CO flux in this oligotrophic seagrass meadow primarily determined the atmospheric cooling effect.