Cold seep systems in the South China Sea: An overview

Dong, Feng; Qiu, Jian‐Wen; Hu, Yu; Peckmann, Jörn; Guan, Huashi; Tong, Hui; Chen, Chong; Chen, Jiangxin; Gong, Shanggui; Li, Niu; Chen, Duofu

doi:10.1016/j.jseaes.2018.09.021

Cited by 206 publications

(150 citation statements)

References 141 publications

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“…Our results suggest that CWCs might record the influence of biogeochemical processes of fluid seepage on bottom water chemistry. The geochemical and isotopic signatures and mineralogy of authigenic carbonates are widely used to trace the composition of ascending fluids, seepage intensities, and associated environmental parameters [78,[82][83][84][85]. The CWCs in seep environments can record rapid changes in ocean chemistry, providing an important constraint on bottom water environmental conditions [26].…”

Section: Cwc Trace-element Contentsmentioning

confidence: 99%

Cold-Water Corals in Gas Hydrate Drilling Cores from the South China Sea: Occurrences, Geochemical Characteristics and Their Relationship to Methane Seepages

Deng

Fang

et al. 2019

Minerals

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Cold-water corals (CWCs) are frequently found at cold seep areas. However, the relationship between fluid seepage and CWC development is not clear. Here, for the first time, we report the occurrences, species identification, mineralogy, carbon and oxygen isotopes, as well as elemental compositions of fossil CWC skeletons from gas-hydrate-bearing sediment in drilling cores from the South China Sea (SCS). Three sites (GMGS-08, GMGS-09B, and GMGS-16) were investigated but CWCs were only found at one site (GMGS-09B). Interestingly, the CWCs were found in three horizons and they were all embedded with authigenic carbonates. Three genera of fossil CWCs (Crispatotrochus sp., Solenosmilia sp. and Enallopsammia sp.) were identified. The CWC fragments are predominantly aragonite. The CWCs exhibit δ13C values between −8.4‰ and −0.6‰ that are significantly higher than δ13C values of the associated seep carbonates (δ13C values with an average of −55.6‰, n = 19), which indicates a carbon source other than methane for the CWCs. It appears that authigenic carbonates provide a substratum for coral colonization. Bathymetric high points, appropriate water temperature and stronger bottom-water currents at site GMGS-09B might be crucial to keep conditions favorable for the growth of CWCs in the studied area. In addition, high trace-element concentrations of Cr, Ni, Pb, U, Ba, Th, and Sr suggest that the CWCs are influenced by strong fluid seepage that can reach the water-sediment interface, and associated microbial activity. Hence, it also becomes evident that CWCs in hydrocarbon-rich seepage areas not only provide a critical constraint on the impact of fluid emission on the bottom water chemistry, but also are likely to be very precise recorders of the end time of cold seep activity.

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Section: Cwc Trace-element Contentsmentioning

confidence: 99%

Cold-Water Corals in Gas Hydrate Drilling Cores from the South China Sea: Occurrences, Geochemical Characteristics and Their Relationship to Methane Seepages

Deng

Fang

et al. 2019

Minerals

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“…Methane seepages are widespread on the northern slope of the South China Sea (SCS) as revealed by authigenic carbonates collected at more than 30 cold seep sites [21][22][23][24][25][26]. The Haima cold seeps were recently discovered on the northwestern slope of SCS [25].…”

Section: Introductionmentioning

confidence: 99%

Methane Source and Turnover in the Shallow Sediments to the West of Haima Cold Seeps on the Northwestern Slope of the South China Sea

et al. 2019

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The Haima cold seeps are active cold seep areas that were recently discovered on the northwestern slope of the South China Sea (SCS). Three piston cores (CL30, CL44, and CL47) were collected within an area characterized by bottom simulating reflectors to the west of Haima cold seeps. Porewater profiles of the three cores exhibit typical kink-type feature, which is attributed to elevated methane flux (CL30) and bubble irrigation (CL44 and CL47). By simulating the porewater profiles of SO42-, CH4, PO43-, Ca2+, Mg2+, and dissolved inorganic carbon (DIC) in CL44 and CL47 using a steady-state reaction-transport model, we estimated that the dissolved SO42- was predominantly consumed by anaerobic oxidation of methane (AOM) at rates of 74.3 mmol m−2 yr−1 in CL44 and 85.0 mmol m−2 yr−1 in CL47. The relatively high AOM rates were sustained by free gas dissolution rather than local methanogenesis. Based on the diffusive Ba2+ fluxes and the excess barium contents in the sediments slightly above the current SMTZ, we estimated that methane fluxes at core CL44 and CL47 have persisted for ca. 3 kyr and 0.8-1.6 kyr, respectively. The non-steady-state modeling for CL30 predicted that a recent increase in upward dissolved methane flux was initiated ca. 85 yr ago. However, the required time for the formation of the barium front above the SMTZ at this core is much longer (ca. 2.2-4.2 kyr), which suggests that the depth of SMTZ possibly has fluctuated due to episodic changes in methane flux. Furthermore, using the model-derived fractions of different DIC sources and the δ13CDIC mass balance calculation, we estimated that the δ13C values of the external methane in cores CL30, CL44, and CL47 are -74.1‰, -75.4‰, and -66.7‰, respectively, indicating the microbial origin of methane. Our results suggest that methane seepage in the broader area surrounding the Haima cold seeps probably has persisted at least hundreds to thousands of years with changing methane fluxes.

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“…Transcriptomic information coupled with gene expression and positive selection analyses can provide a better understanding of the host-symbiont interactions in vesicomyid clams transmitting symbionts vertically. Therefore, in the present study, we sequenced the transcriptome of two vesicomyid clams, Phreagena okutanii (Kojima and Ohta, 1997) from a hydrothermal vent and Archivesica marissinica (Feng et al, 2018) [originally described as "Calyptogena" marissinica C. Chen et al (2018)] from a methane seep (Chen et al, 2018), and compared their transcriptomes with those of shallow-water clam species. Further analysis of the gene expression pattern and genes under positive selection enhanced our understanding of host-symbiont interactions in vesicomyid clams.…”

Section: Introductionmentioning

confidence: 99%

Host–Symbiont Interactions in Deep-Sea Chemosymbiotic Vesicomyid Clams: Insights From Transcriptome Sequencing

et al. 2019

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Cold seep systems in the South China Sea: An overview

Cited by 206 publications

References 141 publications

Cold-Water Corals in Gas Hydrate Drilling Cores from the South China Sea: Occurrences, Geochemical Characteristics and Their Relationship to Methane Seepages

Cold-Water Corals in Gas Hydrate Drilling Cores from the South China Sea: Occurrences, Geochemical Characteristics and Their Relationship to Methane Seepages

Methane Source and Turnover in the Shallow Sediments to the West of Haima Cold Seeps on the Northwestern Slope of the South China Sea

Host–Symbiont Interactions in Deep-Sea Chemosymbiotic Vesicomyid Clams: Insights From Transcriptome Sequencing

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