Blue and black carbon in sabah seagrass and mangrove sediments: its importance for carbon sequestration and storage estimates

• Main Author: Chew, Swee Theng
• Format: Thesis
• Language: English
• Published: 2018
• Subjects: SH Aquaculture. Fisheries. Angling
• Online Access: https://eprints.ums.edu.my/id/eprint/25165/1/Blue%20and%20black%20carbon%20in%20sabah%20seagrass%20and%20mangrove%20sediments.pdf; https://eprints.ums.edu.my/id/eprint/25165/

Blue carbon refers to the carbon stored and sequestered by coastal vegetated ecosystems, for examples, mangroves forest, seagrass meadows and saltmarsh. Along with sequestration, the canopy and rhizome system stabilizes a legacy of hundreds year of buried sedimentary carbon (C) storage from remineralization. The current blue carbon conceptual model estimates C stocks based on the total organic carbon content (TOC) without accounting for deposited allochthonous recalcitrant carbon forms like black carbon (BC). Black carbon is produced outside coastal vegetated ecosystems through the incomplete combustion of fossil fuels and biomass, and is already stable over climatic scales. Hence, a more accurate value of blue carbon storage can only be estimated by subtracting that portion of BC from the TOC. The main objective was, for the first time, to analyze the portion of BC over TOC down the sediment columns of coastal vegetated ecosystem from the seagrass meadows and its adjacent mangrove forest within Salut-Mengkabong lagoon. Black carbon analysis was carried out using two methods, namely, Chemothermal Oxidation (CTO) and Nitric Acid Oxida tion (NAO) to isolate the soot continuum and soot to charcoal continuum, respectively. The top meter C stock for seagrass and mangrove sediment estimated ranging from 6.0 - 203.0 Mg C ha·1 and 139.4 - 425.5 Mg C ha·1 respectively. For organic carbon (OC) sequestration of Enhalus acoroides meadow, estimated ranging from 1.5 - 5.1 Mg C ha·1 yr"1 for Salut upper lagoon and Mengkabong lagoon over "'20 years. However, the results of BC{TOC isolated by CTO and NAO, suggested C stock capacity for seagrass and mangrove will diminish, 1.8 - 66.6 % and 1.4 - 19.6 % respectively. The BC sequestration on the same Enha/us acoroides meadows estimated ranging from 32.6 - 36.0 g m·2 yr"1• Moreover, comparison between temperate and tropical blue carbon ecosystems, suggested current carbon stock estimates are positively biased, particularly for sandy seagrass environs, by 18 ± 3% (±95% confidence interval) and 43 ± 21% (±95% 0) respectively. In conclusion, it is recommended accounting for BC to be included within the blue carbon conceptual model for more accurate assessments in future carbon trading schemes.