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

2019 ◽  
Author(s):  
Chuan Chee Hoe ◽  
John Barry Gallagher ◽  
Chew Swee Theng ◽  
Norlaila Binti Mohd. Zanuri
Keyword(s):  
Carbon Sequestration ◽  
Organic Carbon ◽  
Loss Rate ◽  
Blue Carbon ◽  
Tight Coupling ◽  
Before And After ◽  
Reactivity Continuum ◽  
Particulate Inorganic Carbon

AbstractDetermination of blue carbon sequestration in seagrass sediments over climatic time scales relies on several assumptions, such as no loss of particulate organic carbon (POC) after one or two years, tight coupling between POC loss and CO2emissions, no dissolution of carbonates and removal of the stable 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 and 20–22 cm horizons, respectively. However, the loss rate of POC was far greater than the release rate of CO2, both before and after accounting for CO2from anoxic particulate inorganic carbon (PIC) production, possibly as siderite. The deficit could not be attributed to dissolved organic carbon or dark CO2fixation. 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.

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

2020 ◽  
Vol 71 (8) ◽  
pp. 892 ◽  
Author(s):  
Chee Hoe Chuan ◽  
John Barry Gallagher ◽  
Swee Theng Chew ◽  
M. Zanuri Norlaila Binti
Keyword(s):  
Carbon Sequestration ◽  
Organic Carbon ◽  
Co2 Fixation ◽  
Blue Carbon ◽  
Tight Coupling ◽  
Reactivity Continuum ◽  
Dark Co2 Fixation ◽  
Particulate Inorganic Carbon

Determination of blue carbon sequestration in seagrass sediments over climatic time scales (>100 years) relies on several assumptions, including 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 and 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 20–22-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 sulfate reduction suggested methanogenesis. The results indicated the importance of centennial losses of POC and PIC precipitation and possibly methanogenesis in estimating carbon sequestration rates.

scholarly journals Calcification-driven CO2 emissions exceed “Blue Carbon” sequestration in a carbonate seagrass meadow

2021 ◽  
Author(s):  
Bryce Van Dam ◽  
Mary Zeller ◽  
Christian Lopes ◽  
Ashley Smyth ◽  
Michael Böttcher ◽  
...  
Keyword(s):  
Carbon Dioxide ◽  
Carbon Sequestration ◽  
Organic Carbon ◽  
Seagrass Meadow ◽  
Blue Carbon ◽  
Carbonate Sediments ◽  
Seagrass Meadows ◽  
Carbon Burial ◽  
Organic Carbon Burial

Abstract Long-term “blue carbon” burial in seagrass meadows is complicated by other carbon and alkalinity exchanges that shape net carbon sequestration. We measured a suite of such processes, including denitrification, sulfur, and inorganic carbon cycling, and assessed their impact on air-water carbon dioxide exchange in a typical seagrass meadow underlain by carbonate sediments. Contrary to the prevailing concept of seagrass meadows acting as carbon sinks, eddy covariance measurements reveal this ecosystem as a consistent source of carbon dioxide to the atmosphere, at an average rate of 610 ± 990 µmol m-2 hr-1 during our study and 700 ± 660 µmol m-2 hr-1 over an annual cycle. A robust mass-balance shows that net alkalinity consumption by ecosystem calcification explains >95% of the observed carbon dioxide emissions, far exceeding alkalinity generated by net reduced sulfur, iron and organic carbon burial. Isotope geochemistry of porewaters suggests substantial dissolution and re-crystallization of more stable carbonates mediated by sulfide oxidation-induced acidification, enhancing long-term carbonate burial and ultimate carbon dioxide production. We show that the “blue carbon” sequestration potential of calcifying seagrass meadows has been over-estimated, and that in-situ organic carbon burial only offsets a small fraction (<5%) of calcification-induced CO2 emissions. Ocean-based climate change mitigation activities in such calcifying regions should be approached with caution and an understanding that net carbon sequestration may not be possible.

Ten-year long-term organic fertilization enhances carbon sequestration and calcium-mediated stabilization of aggregate-associated organic carbon in a reclaimed Cambisol

Geoderma ◽  
2019 ◽  
Vol 355 ◽  
pp. 113880 ◽  
Author(s):  
Xiaolei Huang ◽  
Zhixin Jia ◽  
Junjie Guo ◽  
Tingliang Li ◽  
Dasheng Sun ◽  
...  
Keyword(s):  
Carbon Sequestration ◽  
Organic Carbon ◽  
Organic Fertilization

scholarly journals Beyond burial: lateral exchange is a significant atmospheric carbon sink in mangrove forests

2018 ◽  
Vol 14 (7) ◽  
pp. 20180200 ◽  
Author(s):  
Damien T. Maher ◽  
Mitchell Call ◽  
Isaac R. Santos ◽  
Christian J. Sanders
Keyword(s):  
Organic Carbon ◽  
Dissolved Inorganic Carbon ◽  
Carbon Sink ◽  
Blue Carbon ◽  
Mangrove Forests ◽  
Carbon Framework ◽  
Sequestration Potential ◽  
Seagrass Ecosystems ◽  
Atmospheric Carbon

The blue carbon paradigm has evolved in recognition of the high carbon storage and sequestration potential of mangrove, saltmarsh and seagrass ecosystems. However, fluxes of the potent greenhouse gases CH 4 and N 2 O, and lateral export of carbon are often overlooked within the blue carbon framework. Here, we show that the export of dissolved inorganic carbon (DIC) and alkalinity is approximately 1.7 times higher than burial as a long-term carbon sink in a subtropical mangrove system. Fluxes of methane offset burial by approximately 6%, while the nitrous oxide sink was approximately 0.5% of burial. Export of dissolved organic carbon and particulate organic carbon to the coastal zone is also significant and combined may account for an atmospheric carbon sink similar to burial. Our results indicate that the export of DIC and alkalinity results in a long-term atmospheric carbon sink and should be incorporated into the blue carbon paradigm when assessing the role of these habitats in sequestering carbon and mitigating climate change.

scholarly journals Impact of Clay Mineralogy on Stabilization of Soil Organic Carbon for Long-Term Carbon Sequestration

2017 ◽  
Vol 6 (5) ◽  
pp. 2157-2167 ◽  
Author(s):  
Ravi Kumar Meena ◽  
Anil Kumar Verma ◽  
Chiranjeev Kumawat ◽  
Brijesh Yadav ◽  
Atul B. Pawar ◽  
...  
Keyword(s):  
Carbon Sequestration ◽  
Organic Carbon ◽  
Soil Organic Carbon ◽  
Clay Mineralogy

scholarly journals Inorganic and black carbon hotspots constrain blue carbon mitigation services across tropical seagrass and temperate tidal marshes

2021 ◽  
Author(s):  
John Barry Gallagher ◽  
Vishnu Prahalad ◽  
John Aalders
Keyword(s):  
Salt Marsh ◽  
Organic Carbon ◽  
Salt Marshes ◽  
Inorganic Carbon ◽  
Blue Carbon ◽  
Tidal Marshes ◽  
Carbon Mitigation ◽  
Seagrass Meadows ◽  
First Time ◽  
Particulate Inorganic Carbon

Abstract Total organic carbon (TOC) sediment stocks as a CO2 mitigation service require exclusion of allochthonous black (BC) and particulate inorganic carbon corrected for water–atmospheric equilibrium (PICeq). For the first time, we address this bias for a temperate salt marsh and a coastal tropical seagrass in BC hotspots that represent two different blue carbon ecosystems of Malaysia and Australia. Seagrass TOC stocks were similar to the salt marshes with soil depths < 1 m (59.3 ± 11.3 and 74.9 ± 18.9 MgC ha− 1, CI 95% respectively). Both ecosystems showed larger BC constraints than their pristine counterparts did. However, the seagrass meadows’ mitigation services were largely constrained by both higher BC/TOC and PICeq/TOC fractions (38.0% ± 6.6% and 43.4% ± 5.9%, CI 95%) and salt marshes around a third (22% ± 10.2% and 6.0% ± 3.1% CI 95%). The results provide useful data from underrepresented regions, and, reiterates the need to consider both BC and PIC for more reliable blue carbon mitigation assessments.

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