Carbon Storage in Rock Garden Seagrass Bed, Rayong Province

Abstract

Seagrass meadows are important coastal ecosystems providing many ecological services including acting as natural sinks for carbon storage and sequestration and thereby offering solutions to mitigate climate change caused by elevated atmospheric carbon dioxide concentration. However, most seagrass beds have been threatened by coastal developments and various other anthropogenic activities. This may in turn reduce the amount of carbon stored in coastal ecosystems (i.e., blue carbon). As a result, this study aims at assessing organic carbon storage in the seagrass beds at Rock Garden Village, which are the largest beds in terms of area in Rayong Province. Sediment and seagrass from 19 sediment cores as predetermined by distributed probability-based grid method were collected in November and December 2020. The organic carbon content was determined by using the elemental analyzer. Two seagrass species present in the study area were Halodule pinifolia and Halodule uninervis. They were both found in sediments made up mostly of sand. In sediments, carbon concentration inside the seagrass patch was significantly (p < 0.05) higher (0.97 ± 0.68 mg C/g) than those outside the patch (0.46 ± 0.11 mg C/g). Overall, the H. uninervis stored more organic carbon (0.09 ± 0.05 kg C/m²) than the H. pinifolia (0.06 ± 0.05 kg C/m²). Furthermore, H. uninervis preferentially stores carbon in below-ground parts (i.e., rhizomes and roots), whereas H. pinifolia preferentially stores carbon in above-ground parts (i.e., leaf blades and leaf sheaths). This study emphasizes the importance of organic carbon accumulation in seagrass, along with the relationship between organic carbon accumulation in each species of seagrass and in each part of seagrass, which will lead to development of seagrass ecosystem conservation.