Sedimentary seagrass carbon stock and sources of organic carbon in small islands of Indonesia: comparing meadows inside and outside Marine Protected Areas

Abstract

Abstract Seagrass meadows are an important component of coastal ecosystems globally, and they capture and store organic carbon in living biomass and sediments. Geographical estimates of blue carbon in seagrass habitats are regionally biased, with limited information from the Indo-Pacific region, including Indonesia. Seagrass extent in Indonesia is declining rapidly, and it has been suggested that Marine Protected Areas (MPAs) are an important instrument to support protection of seagrass ecosystems and its services. Thus, our study aimed to quantify and to compare sedimentary carbon stocks and sources of organic carbon in seagrass meadows located in undisturbed areas outside MPA, disturbed areas outside MPA, and within MPA in three small islands in Indonesia. The sediment carbon stocks ranged from 19.81 to 117.49 Mg C ha− 1, with the highest stock measured inside MPA (77.15 ± 1.38 Mg C ha− 1), followed by undisturbed outside MPA (36.08 Mg C ha− 1), and lowest stock at disturbed outside MPA (21.86 ± 0.31 Mg C ha− 1). The predominant source of organic carbon in disturbed meadows was from coastal POM (~ 36%), while in MPA and undisturbed site the main source was seagrass, with ~ 38% and ~ 60%, respectively. The results of this study highlight the influence of MPAs on conserving carbon stock in seagrass ecosystems and provide important information on the importance of MPA’s in avoiding emissions caused by remineralisation of sediment organic carbon following seagrass degradation.