An Areal Assessment of Subseafloor Carbon Cycling in Cold Seeps and Hydrate-Bearing Areas in the Northern South China Sea

Zhang, Yanping; Luo, Min; Hu, Yu; Wang, Hongbin; Chen, Duofu

doi:10.1155/2019/2573937

Cited by 12 publications

(21 citation statements)

References 75 publications

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“…As a result of MSiW, methanogenic DIC contributes as alkalinity, and silicate-bond cations are released (Wallmann et al, 2008;Solomon et al, 2014;Pierre et al, 2016), resulting in deep-DIC sequestration via carbonate precipitation within methanogenic zones (Torres et al, 2020). Additional deep-DIC sinks coupled to Fe/Mn reduction in the methanogenic zones was proposed by Solomon et al (2014) and available literature reports also show a lower deep-DIC flux rate (Dickens and Snyder, 2009;Chatterjee et al, 2011;Wehrmann et al, 2011;Komada et al, 2016;Hu et al, 2017;Zhang et al, 2019). Hence, we assume a conservative estimate of 50% of CH 4 flux to our budget as the average F (DIC−deep) .…”

Section: Estimations Of Parameter Valuesmentioning

confidence: 99%

“…Reported average DIC uptake by authigenic carbonates from the total DIC pool at the SMTZ varies from 7-36% (Luff and Wallmann, 2003;Snyder et al, 2007;Wallmann et al, 2008;Hong et al, 2013;Coffin et al, 2014;Komada et al, 2016;Chuang et al, 2019;Zhang et al, 2019), with upper estimates ranging up to 50% (Smith and Coffin, 2014). However, it is important to note that authigenic carbonates may not precipitate at all methane flux settings.…”

Section: F Carbmentioning

confidence: 99%

“…This approach also considers the still-limited global perspective of these parameters. 50% 20-75% Luff and Wallmann, 2003;Snyder et al, 2007;Wallmann et al, 2008;Hong et al, 2013;Coffin et al, 2014;Komada et al, 2016;Hu et al, 2017;Chuang et al, 2019;Zhang et al, 2019 F carb 20% 10-35% Luff and Wallmann, 2003;Wallmann et al, 2006;Snyder et al, 2007;Karaca et al, 2010;Hong et al, 2013;Coffin et al, 2014;Komada et al, 2016;Hu et al, 2017;Chuang et al, 2019;Zhang et al, 2019 F SOM 5% 1-10% Nauhaus et al, 2007;Sivan et al, 2007;Treude et al, 2007;Ussler and Paull, 2008;Contreras et al, 2013;Coffin et al, 2014;Jørgensen et al, 2019a F (DIC−out) 75% 50-90% Aloisi et al, 2004;Wallmann et al, 2008;Dickens and Snyder, 2009;Chatterjee et al, 2011;Wehrmann et al, 2011;Scholz et al, 2013;Solomon et al, 2014;Zhang et al, 2019 DIC Production via AOM and OSR…”

Section: F Socmentioning

confidence: 99%

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Dissolved Inorganic Carbon Pump in Methane-Charged Shallow Marine Sediments: State of the Art and New Model Perspectives

et al. 2020

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Methane transport from subsurface reservoirs to shallow marine sediment is characterized by unique biogeochemical interactions significant for ocean chemistry. Sulfate-Methane Transition Zone (SMTZ) is an important diagenetic front in the sediment column that quantitatively consumes the diffusive methane fluxes from deep methanogenic sources toward shallow marine sediments via sulfate-driven anaerobic oxidation of methane (AOM). Recent global compilation from diffusion-controlled marine settings suggests methane from below and sulfate from above fluxing into the SMTZ at an estimated rate of 3.8 and 5.3 Tmol year −1 , respectively, and wider estimate for methane flux ranges from 1 to 19 Tmol year −1. AOM converts the methane carbon to dissolved inorganic carbon (DIC) at the SMTZ. Organoclastic sulfate reduction (OSR) and deep-DIC fluxes from methanogenic zones contribute additional DIC to the shallow sediments. Here, we provide a quantification of 8.7 Tmol year −1 DIC entering the methane-charged shallow sediments due to AOM, OSR, and the deep-DIC flux (range 6.4-10.2 Tmol year −1). Of this total DIC pool, an estimated 6.5 Tmol year −1 flows toward the water column (range: 3.2-9.2 Tmol year −1), and 1.7 Tmol year −1 enters the authigenic carbonate phases (range: 0.6-3.6 Tmol year −1). This summary highlights that carbonate authigenesis in settings dominated by diffusive methane fluxes is a significant component of marine carbon burial, comparable to ∼15% of carbonate accumulation on continental shelves and in the abyssal ocean, respectively. Further, the DIC outflux through the SMTZ is comparable to ∼20% of global riverine DIC flux to oceans. This DIC outflux will contribute alkalinity or CO 2 in different proportions to the water column, depending on the rates of authigenic carbonate precipitation and sulfide oxidation and will significantly impact ocean chemistry and potentially atmospheric CO 2. Settings with substantial carbonate precipitation and sulfide oxidation at present are contributing CO 2 and thus to ocean acidification. Our synthesis emphasizes the importance of SMTZ as not only a methane sink but also an important diagenetic front for global DIC cycling. We further underscore the need to incorporate a DIC pump in methane-charged shallow marine sediments to models for coastal and geologic carbon cycling.

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Section: Estimations Of Parameter Valuesmentioning

confidence: 99%

Section: F Carbmentioning

confidence: 99%

Section: F Socmentioning

confidence: 99%

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Dissolved Inorganic Carbon Pump in Methane-Charged Shallow Marine Sediments: State of the Art and New Model Perspectives

et al. 2020

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“…Seabed Methane Seepage. Seabed methane seepage represents the transfer of methane from the geosphere to hydrosphere, biosphere, or even atmosphere, which is regarded as a process of the Earth's carbon recycling [25,26]. Seabed methane seepage features can occur globally at different geological settings including active margins (e.g., convergent margin, accretionary margin, erosive margins, and transform margins) and passive margins [25,27].…”

Section: Geological Conditionsmentioning

confidence: 99%

“…Seabed methane seepage features can occur globally at different geological settings including active margins (e.g., convergent margin, accretionary margin, erosive margins, and transform margins) and passive margins [25,27]. Seepage fluid composition often includes water, free gas (especially methane), and some sediments, and they transfer from different sources upwards to the seafloor by different forcing mechanisms such as sediment compaction, methane overpressure caused by gas hydrate dissociation, biogeochemical reactions, biological activities, overpressure, and facies changes [25,26,28]. Apart from seabed seepage manifestations (e.g., pockmarks, deep-water corals, and authigenic carbonate crusts on mounds or pavements), fluid conduit features (such as slope failures, faults, mud volcanoes, scars, scarps, and bulges) also play a big role in facilitating fluid escape and seabed methane seepage formation [29,30].…”

Section: Geological Conditionsmentioning

confidence: 99%

A Geophysical Review of the Seabed Methane Seepage Features and Their Relationship with Gas Hydrate Systems

Yang

Zheng

et al. 2021

Geofluids

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Seabed methane seepage has gained attention from all over the world in recent years as an important source of greenhouse gas emission, and gas hydrates are also regarded as a key factor affecting climate change or even global warming due to their shallow burial and poor stability. However, the relationship between seabed methane seepage and gas hydrate systems is not clear although they often coexist in continental margins. It is of significance to clarify their relationship and better understand the contribution of gas hydrate systems or the deeper hydrocarbon reservoirs for methane flux leaking to the seawater or even the atmosphere by natural seepages at the seabed. In this paper, a geophysical examination of the global seabed methane seepage events has been conducted, and nearby gas hydrate stability zone and relevant fluid migration pathways have been interpreted or modelled using seismic data, multibeam data, or underwater photos. Results show that seabed methane seepage sites are often manifested as methane flares, pockmarks, deep-water corals, authigenic carbonates, and gas hydrate pingoes at the seabed, most of which are closely related to vertical fluid migration structures like faults, gas chimneys, mud volcanoes, and unconformity surfaces or are located in the landward limit of gas hydrate stability zone (LLGHSZ) where hydrate dissociation may have released a great volume of methane. Based on a comprehensive analysis of these features, three major types of seabed methane seepage are classified according to their spatial relationship with the location of LLGHSZ, deeper than the LLGHSZ (A), around the LLGHSZ (B), and shallower than LLGHSZ (C). These three seabed methane seepage types can be further divided into five subtypes considering whether the gas source of seabed methane seepage is from the gas hydrate systems or not. We propose subtype B2 represents the most important seabed methane seepage type due to the high density of seepage sites and large volume of released methane from massive focused vigorous methane seepage sites around the LLGHSZ. Based on the classification result of this research, more measures should be taken for subtype B2 seabed methane seepage to predict or even prevent ocean warming or climate change.

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An Epifaunal Community Succession Sequence Driven by the Biogeochemical Footprint With Different Methane Seepage Intensity of the Deep Seafloor

Zhang,

Feng,

Shen

et al. 2023

Earth's Future

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Methane seepage, generated from natural processes or gas hydrate dissociation, drives the development of cold seep ecosystems and leads to atmosphere methane emission, thereby influencing climate change. Uncovering the intrinsic interactions among methane seepage intensities, biogeochemical processes in the sediment, and benthic community characteristics at the seafloor is essential to clarify and predict the ultimate fate of methane leakage from the deep sea. Here, we conducted a systematic investigation of methane intensity, pore fluid migration characteristics, sediment mineral fraction features, and the evolution of biological communities in areas with different methane intensities. Furthermore, analyses of high‐resolution images, pore fluid geochemical feature, and lithologic characteristics of the sediment in the Haima cold seep were also carried out in this study. The results showed that, in areas with different methane intensities, organic matter sulfate reduction and anaerobic oxidation of methane were heterogeneous. The heterogeneity led to the methane transformation zones at different depths, which changed the mineral composition of the sediment and biological communities in the seabed. In addition, a hypothesis of successional sequence of biomes in cold seep was established. This study revealed that the methane seepage intensity was a key factor in determining the biogeochemical process in the sediment of cold seep. The coupling effects of biogeochemical processes and methane seepage intensities dominated the community succession of cold seep. These findings could provide important implications for understanding the dynamic deep marine methane cycle mechanism and the contribution of deep‐sea methane released to climate change.

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An Areal Assessment of Subseafloor Carbon Cycling in Cold Seeps and Hydrate-Bearing Areas in the Northern South China Sea

Cited by 12 publications

References 75 publications

Dissolved Inorganic Carbon Pump in Methane-Charged Shallow Marine Sediments: State of the Art and New Model Perspectives

Dissolved Inorganic Carbon Pump in Methane-Charged Shallow Marine Sediments: State of the Art and New Model Perspectives

A Geophysical Review of the Seabed Methane Seepage Features and Their Relationship with Gas Hydrate Systems

An Epifaunal Community Succession Sequence Driven by the Biogeochemical Footprint With Different Methane Seepage Intensity of the Deep Seafloor

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