Valuing carbon stocks across a tropical lagoon after accounting for black and inorganic carbon: bulk density proxies for monitoring

• Main Authors: John Barry Gallagher, Swee, Theng Chew, John Madin, Anitra Thorhaug
• Format: Article
• Language: English
• Published: Coastal Education and Research Foundation, Inc. 2020
• Subjects: SH Aquaculture. Fisheries. Angling
• Online Access: https://eprints.ums.edu.my/id/eprint/26698/1/Valuing%20Carbon%20Stocks%20across%20a%20Tropical%20Lagoon%20after%20Accounting%20for%20Black%20and%20Inorganic%20Carbon.pdf; https://eprints.ums.edu.my/id/eprint/26698/; https://doi.org/10.2112/JCOASTRES-D-19-00127.1
• Institution: Universiti Malaysia Sabah

Total organic carbon (TOC) stocks of seagrass and mangroves across a Southeast Asian lagoon were measured and valued after correcting for black carbon (BC) and calcareous carbon equivalents (PICequiv) in mitigating CO2 emissions, along with sediment dry bulk densities (DBDs), as a cost-effective means of estimating carbon stock concepts. Overall, seagrass and mangrove TOC densities ranged from 15.3 ± 4.3 and 124.3 ± 21.1 Mg C ha–1, respectively, across the lower lagoon and 175.2 ± 46.9 and 103.2 ± 19.0 Mg C ha–1 for seagrass and 355.0 ± 24.8 and 350.3 ± 35.2 Mg C ha–1 for mangroves across the two upper lagoon branches. Only mangrove biomass made significant additional contributions, ranging from 178.5 ± 62.3 to 120.7 ± 94.8 Mg C ha–1 for lower and upper regions, respectively. The difference between the lagoon's seagrass and mangrove TOC total stock (5.98 ± 0.69 and 390 ± 33.22 Gg C, respectively) was further amplified by the larger mangrove area. When corrected for BC and PICequiv, the carbon stock mitigation service was reduced by a moderate 14.2%. Across the lagoon the sedimentary DBD showed strong (R2 = 0.85, p < 0.001) to moderate (R2 = 0.67, p < 0.001) linear correlations with seagrass and mangrove [TOC], respectively and moderate correlations with seagrass [PIC] (R2 = 0.6, p < 0.001). There was an invariant and relatively constant response to mangrove [PIC] (2.7 ± 0.07 kg m–3). Valuations were worth on average US$0.44 million y–1 over 20 years, and less than the total income of the indigenous custodians (US$1.8 and US$7.4 million y–1).