A preliminary study of carbon dioxide and methane emissions from patchy tropical seagrass meadows in Thailand

Seagrass meadows are a significant blue carbon sink due to their ability to store large amounts of carbon within sediment. However, the knowledge of global greenhouse gas (GHG) emissions from seagrass meadows is limited, especially from meadows in the tropical region. Therefore, in this study, CO₂ and CH₄ emissions and carbon metabolism were studied at a tropical seagrass meadow under various conditions.

CO₂ and CH₄ emissions and carbon metabolism were measured using benthic chambers deployed for 18 h at Koh Mook, off the southwest coast of Thailand. The samples were collected from areas of patchy Enhalus acoroides, Thalassia hemprichii, and bare sand three times within 18 h periods of incubation: at low tide at 6 pm (t0), at low tide at 6 am (t1), and at high tide at noon (t2).

Seagrass meadows at Koh Mook exhibited varying CO₂ and CH₄ emissions across different sampling areas. CO₂ emissions were higher in patchy E. acoroides compared to patchy T. hemprichii and bare sand areas. CH₄ emissions were only detected in vegetated areas (patchy E. acoroides and T. hemprichii) and were absent in bare sand. Furthermore, there were no significant differences in net community production across sampling areas, although seagrass meadows were generally considered autotrophic. Koh Mook seagrass meadows contribute only slightly to GHG emissions. The results suggested that the low GHG emissions from Koh Mook seagrass meadows do not outweigh their role as significant carbon sinks, with a value 320 t CO_{2 -eq}. This study provided baseline information for estimating GHG emissions in seagrass meadows in Thailand.