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Blue carbon sequestration dynamics within tropical seagrass sediments: long-term incubations for changes over climatic scales


Chuan, CH and Gallagher, JB and Chew, ST and Binti, MZN, Blue carbon sequestration dynamics within tropical seagrass sediments: long-term incubations for changes over climatic scales, Marine and Freshwater Research, 71, (8) pp. 892-904. ISSN 1323-1650 (2020) [Refereed Article]

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Copyright 2020 CSIRO

DOI: doi:10.1071/MF19119


Determination of blue carbon sequestration in seagrass sediments over climatic time scales (>100 years) relies on several assumptions: no loss of particulate organic carbon (POC) after 1-2 years; tight coupling between POC loss and CO2 emissions; no dissolution of carbonates; and removal of the recalcitrant black carbon (BC) contribution. We tested these assumptions via 500-day anoxic decomposition/mineralisation experiments to capture centennial parameter decay dynamics from two sediment horizons robustly dated as 2 and 18 years old. No loss of BC was detected, and decay of POC was best described for both horizons by near-identical reactivity continuum models. The models predicted average losses of 49% and 51% after 100 years of burial for the surface and 2022 cm horizons respectively. However, the loss rate of POC was far greater than the release rate of CO2, even after accounting for CO2 from particulate inorganic carbon (PIC) production, possibly as siderite. The deficit could not be attributed to dissolved organic carbon or dark CO2 fixation. Instead, evidence based on δ13CO2, acidity and lack of sulphate reduction suggested methanogenesis. The results indicate the importance of centennial losses of POC and PIC precipitation and possibly methanogenesis in estimating carbon sequestration rates.

Item Details

Item Type:Refereed Article
Keywords:carbonate, diagenesis, methane, pyrogenic carbon, sediment geochemistry, sediment isotope tomography
Research Division:Environmental Sciences
Research Group:Climate change impacts and adaptation
Research Field:Carbon sequestration science
Objective Division:Environmental Management
Objective Group:Management of Antarctic and Southern Ocean environments
Objective Field:Assessment and management of Antarctic and Southern Ocean ecosystems
UTAS Author:Gallagher, JB (Dr John Barry Gallagher)
ID Code:137941
Year Published:2020
Web of Science® Times Cited:5
Deposited By:Oceans and Cryosphere
Deposited On:2020-03-16
Last Modified:2020-12-07
Downloads:4 View Download Statistics

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