Pore‐water exchange flushes blue carbon from intertidal saltmarsh sediments into the sea

Chen, Xiaogang; Santos, Isaac R.; Hu, Duofei; Zhan, Lucheng; Zhang, Yan; Zhao, Ze; Hu, Shengjie; Li, Ling

doi:10.1002/lol2.10236

Cited by 34 publications

(11 citation statements)

References 44 publications

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“…Part of the sediment organic carbon is decomposed into dissolved inorganic carbon (DIC) and dissolved organic carbon (DOC). Both DIC and DOC are exported to the coastal ocean through tidally derived pore‐water exchange (Correa et al 2021; Tamborski et al 2021; Chen et al 2022).…”

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confidence: 99%

Alkalinity export to the ocean is a major carbon sequestration mechanism in a macrotidal saltmarsh

Yau

Xin

Chen

et al. 2022

Limnology & Oceanography

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Saltmarshes are a blue carbon ecosystem accumulating large quantities of organic carbon in sediments. Some of this carbon can be transformed into dissolved inorganic carbon (DIC) and methane (CH 4 ) that may eventually be exported to the ocean or atmosphere. Although extensive studies have quantified specific components of the carbon budget such as carbon burial, limited attention has been given to pore-water-derived carbon and total alkalinity (TA) exports to the ocean. Here, we quantified lateral exports to the ocean (outwelling) of 202 AE 160 and 78 AE 75 mmol m À2 d À1 of DIC and TA, respectively. The TA : DIC concentration ratio in the creek waters was $ 1, implying TA production from anaerobic mineralization in sediments. The lateral TA exports were comparable to the local (94 AE 48 mmol m À2 d À1 ) and national ($ 50 mmol m À2 d À1 ) organic carbon burial. High TA exports could locally increase the ocean buffering capacity and contribute bicarbonate to the coastal ocean, acting as a long-term carbon storage. Pore water traced by radon contributed 28-37% and 58-69% of DIC and TA exports. Separating the two major DIC components (i.e., CO 2 emissions and alkalinity exports) is essential to resolve the carbon sequestration potential from saltmarshes. Here, dissolved CO 2 emissions to the atmosphere accounted for 3-5% of total DIC outwelling. CH 4 emissions played a minor role offsetting around 0.3 to 6% of the carbon sequestration. Overall, we demonstrate that alkalinity export into the ocean can be an overlooked carbon sequestration pathway in saltmarshes at rates comparable to carbon burial.

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confidence: 99%

Alkalinity export to the ocean is a major carbon sequestration mechanism in a macrotidal saltmarsh

Yau

Xin

Chen

et al. 2022

Limnology & Oceanography

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“…The low‐DO events could be caused by the increased heterotrophic respiration driven by the DOC fluxes from the marshes or oxygen demand from the sediment of the tidal marshes (e.g., diffused sulfide). The material that is exported from the tidal marshes has been observed to be dominated by organic carbon or inorganic carbon at different times or locations (Chen et al., 2022; Czapla et al., 2020; Feijtel et al., 1985; Jordan et al., 1983; Knobloch et al., 2021; Koch & Gobler, 2009; Tzortziou et al., 2011). Currently, the marsh model in this study allows both exports of organic carbon and low sediment redox potential that consumes oxygen demand to fit the observations.…”

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confidence: 99%

The Roles of Tidal Marshes in the Estuarine Biochemical Processes: A Numerical Modeling Study

Cai

Shen²,

Zhang³

et al. 2023

JGR Biogeosciences

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Highly productive tidal marshes play a key role in the estuarine ecosystem by affecting the dynamics of carbon, nitrogen, phosphorus, and oxygen (Bridgham et al., 2006;Chmura et al., 2003). Sedimentation is greatly enhanced in the tidal marshes due to enhanced flow impedance locally and the tidal marshes tend to be traps of particulate material, therefore retaining a significant amount of carbon and other nutrients (

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“…Radon ( 222 Rn, t 1/2 = 3.8 d) is a powerful tracer for studying geophysical processes including submarine groundwater discharge (SGD) (Burnett and Dulaiova, 2006;Lopez et al, 2020), air-sea gas exchange (Rutgers van der Loeff et al, 2014), sediment-water diffusion (Corbett et al, 1998), and earthquake prediction (Kuo et al, 2010). Recent climate studies combine radon data with biogenic gases (e.g., CH 4 and CO 2 ) to evaluate the SGD's contribution to atmospheric greenhouse gas budgets (Santos et al, 2019;Chen et al, 2022). Radon-in-water measurements are commonly performed either by discrete grab sampling followed by laboratory analyses (gas extraction, Lucas cells) or by continuous on-site measurements (RAD AQUA-RAD7).…”

Section: Introductionmentioning

confidence: 99%

In-situ radon-in-water detection for high resolution submarine groundwater discharge assessment

Zhao

Burnett

et al. 2022

Front. Mar. Sci.

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Submarine groundwater discharge (SGD), including both land-based fresh groundwater that enters the ocean from coastal aquifers as well as recirculated seawater that is continuously recharged and discharged on the seabed, has been considered as an important component of the global water and biogenic element (e.g., nitrogen, phosphorus, silicon and carbon) sources and a significant pathway for material exchange at the land-sea interface of coastal ecosystems. Some researchers reported that SGD associated nutrient additions to coastal waters have caused unwanted ecological issues, including red tides, coastal acidification and hypoxia. Natural radon isotope (222Rn, t1/2 = 3.8 d) is an excellent tracer for studying SGD and other oceanographic processes including air-sea gas exchange, sediment-water diffusion, and earthquake prediction. However, the conventional radon measurement methods suffer many technical disadvantages. We consequently developed a convenient submersible radon determination approach (“OUC-Rn”) using a commercial pulsed ionization chamber (PIC) radon sensor and gas extraction membrane module to produce high precision and high resolution observations. We demonstrate the radon degassing efficiency of the membrane contactor is comparable to the shower-head type air-water exchanger but is independent of operating position. The radon measurement efficiency of the PIC is 2-fold higher than the RAD7 detector and is far less influenced by moisture. We successfully deployed the system in 2.5 meters water depth over a 100 hours period in an anthropogenic influenced bay. Based on our high temporal resolution observations, the SGD flux was estimated to be 0-43.0 cm/d (mean: 25.4 ± 14.5 cm/d). The SGD fluxes pattern plotted together with the tidal variations revealed that tidal pumping may be the main force driving seawater recirculation into aquifers and thus affecting nutrient, carbon and other dissolved matters dynamics in coastal regions.

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Pore‐water exchange flushes blue carbon from intertidal saltmarsh sediments into the sea

Cited by 34 publications

References 44 publications

Alkalinity export to the ocean is a major carbon sequestration mechanism in a macrotidal saltmarsh

Alkalinity export to the ocean is a major carbon sequestration mechanism in a macrotidal saltmarsh

The Roles of Tidal Marshes in the Estuarine Biochemical Processes: A Numerical Modeling Study

In-situ radon-in-water detection for high resolution submarine groundwater discharge assessment

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