Sedimentary seagrass carbon stock and sources of organic carbon in small islands of Indonesia
Yusmiana P. Rahayu*1,2, Mariska A. Kusumaningtyas2, August Daulat2, Agustin Rustam2, Devi D. Suryono2, Hadiwijaya L. Salim2, Restu N. A. Ati2, Nasir Sudirman2, Terry L. Kepel3, Andreas A. Hutahaean4, Novi S. Adi5

1School of Biological Sciences, and Ocean Institute, the University of Western Australia, 35 Stirling Highway, Crawley, WA 6009, Australia
2Research Center for Conservation of Marine and Inland Water Resources, the National Research and Innovation Agency, the Republic of Indonesia, Soekarno Science and Technology Area, Jl. Raya Bogor Km 46, Cibinong, Bogor 16911, Indonesia
3Research Center for Oceanography, the National Research and Innovation Agency, the Republic of Indonesia, Ancol Science Area, Jl. Pasir Putih I, Ancol, Jakarta 14430, Indonesia
4Coordinating Ministry for Maritime Affairs and Investment Republic of Indonesia, Jl. M.H. Thamrin No. 8, Jakarta Pusat 10340, Indonesia
5Ministry of Marine Affairs and Fisheries, the Republic of Indonesia, Gedung Mina Bahari III, Lt.11, Jl. Medan Merdeka Timur No. 16, Jakarta Pusat 10340, Indonesia

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 their services. Thus, this study aimed to quantify and compare sedimentary carbon stocks and sources of organic carbon from 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 from this study ranged from 19.81 to 117.49 Mg C/ha, with the highest stock measured inside MPA (77.15 Mg C/ha), followed by undisturbed outside MPA (36.08 Mg C/ha), and the lowest stock at disturbed outside MPA (21.86 Mg C/ha). The predominant source of organic carbon in disturbed meadows was from coastal POM (particulate organic matter, 36%), while in MPA and undisturbed sites the main source was from seagrass, with 38% and 60% contributions, respectively. The results of this study highlight the potential of MPAs for conserving carbon stock in seagrass ecosystems and provide important information on the importance of MPAs in avoiding emissions caused by remineralisation of sediment organic carbon following seagrass degradation.

Keywords: blue carbon, isotopes, organic carbon, climate change, MPA, conservation

Topic: Marine Resources, and Conservation