Lipid biomarker patterns reflect seepage activity and variable geochemical processes in sediments from the Haima cold seeps, South China Sea

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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Corrigendum to “Vertical shifts of particle-attached and free-living prokaryotes in the water column above the cold seeps of the South China Sea” [Mar. Pollut. Bull. Volume 156, July 2020, 111,230]

Marine Pollution Bulletin ◽

10.1016/j.marpolbul.2020.111472 ◽

2020 ◽

Vol 158 ◽

pp. 111472

Author(s):

Yue Zhang ◽

Hongmei Jing ◽

Xiaotong Peng

Keyword(s):

South China Sea ◽

Water Column ◽

South China ◽

The South China Sea ◽

Cold Seeps ◽

The South ◽

Free Living ◽

China Sea

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Gas Hydrate Accumulation and Occurrence Associated with Cold Seep Systems in the Northern South China Sea: An Overview

Geofluids ◽

10.1155/2021/5571150 ◽

2021 ◽

Vol 2021 ◽

pp. 1-24

Author(s):

Wei Zhang ◽

Jinqiang Liang ◽

Qianyong Liang ◽

Jiangong Wei ◽

Zhifeng Wan ◽

...

Keyword(s):

South China Sea ◽

South China ◽

Gas Hydrates ◽

Gas Hydrate ◽

Northern South China Sea ◽

Cold Seep ◽

Cold Seeps ◽

Associated Gas ◽

China Sea ◽

Gas Bearing

Studying deep-water cold seep systems is of great significance to gas hydrate exploration due to their close relationship. Various cold seep systems and related gas hydrate accumulations have been discovered in the northern South China Sea in the past three decades. Based on high-resolution seismic data, subbottom profiles, in situ submergence observations, deep drilling and coring, and hydrate gas geochemical analyses, the geological and geophysical characteristics of these cold seep systems and their associated gas hydrate accumulations in the Qiongdongnan Basin, the Shenhu area, the Dongsha area, and the Taixinan Basin have been investigated. Cold seep systems are present in diverse stages of evolution and exhibit various seabed microgeomorphic, geological, and geochemical features. Active cold seep systems with a large amount of gas leakage, gas plumes, and microbial communities and inactive cold seep systems with authigenic carbonate pavements are related to the variable intensity of the gas-bearing fluid, which is usually derived from the deep strata through mud diapirs, mud volcanoes, gas chimneys, and faults. Gas hydrates are usually precipitated in cold seep vents and deeper vertical fluid migration pathways, indicating that deep gas-bearing fluid activities control the formation and accumulation of gas hydrates. The hydrocarbons collected from cold seep systems and their associated gas hydrate reservoirs are generally mixtures of biogenic gas and thermogenic gas, the origin of which is generally consistent with that of deep conventional gas. We also discuss the paragenetic relationship between the gas-bearing fluid and the seafloor morphology of cold seeps and the deep-shallow coupling of gas hydrates, cold seeps, and deep petroleum reservoirs. It is reasonable to conclude that the deep petroleum systems and gas-bearing fluid activity jointly control the development of cold seep systems and the accumulation of gas hydrates in the northern South China Sea. Therefore, the favorable areas for conventional oil and gas enrichment are also prospective areas for exploring active cold seeps and gas hydrates.

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Corrigendum: Active Anaerobic Archaeal Methanotrophs in Recently Emerged Cold Seeps of Northern South China Sea

Frontiers in Microbiology ◽

10.3389/fmicb.2021.653239 ◽

2021 ◽

Vol 12 ◽

Author(s):

Tingting Zhang ◽

Xi Xiao ◽

Songze Chen ◽

Jing Zhao ◽

Zongheng Chen ◽

...

Keyword(s):

South China Sea ◽

South China ◽

Northern South China Sea ◽

Cold Seeps ◽

China Sea

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The Diversity, Composition, and Putative Functions of Gill-Associated Bacteria of Bathymodiolin Mussel and Vesicomyid Clam from Haima Cold Seep, South China Sea

Microorganisms ◽

10.3390/microorganisms8111699 ◽

2020 ◽

Vol 8 (11) ◽

pp. 1699

Author(s):

Juan Ling ◽

Hongxiang Guan ◽

Lihua Liu ◽

Jun Tao ◽

Jie Li ◽

...

Keyword(s):

South China Sea ◽

South China ◽

Phylogenetic Diversity ◽

High Throughput Sequencing ◽

Cold Seep ◽

Rrna Gene ◽

Cold Seeps ◽

Element Cycling ◽

China Sea ◽

Vesicomyid Clam

The Haima cold seep, which is one of the two active cold seeps in the South China Sea, is known for its great ecological importance. The seep bivalves are assumed to depend mainly on their bacterial symbiosis for survival and growth. However, information on the bacterial diversity, composition, and putative function of gill-associated of dominant dwelling animals in Haima cold seep remain elusive. Herein, we adopted a high-throughput sequencing of 16S rRNA gene amplicons, and function prediction methods (Functional Annotation of Prokaryotic Taxa (FAPROTAX) and Phylogenetic Investigation of Communities by Reconstruction of Unobserved States (PICURUSTs)) to purposely illustrate the taxonomic and phylogenetic diversity, composition, and putative functions of the symbionts in bathymodiolin mussel Gigantidas haimaensis (Bivalvia: Mytilidae: Gigantidas) and vesicomyid clam Archivesica marissinica (Bivalvia: Glossoidea: Vesicomyidae). The predominant microbes of both species were Proteobacteria and Gammaproteobacteria on the phylum and class level, respectively. The taxonomic and phylogenetic diversity of gill microbial communities in G. haimaensis were significantly different from those in A. marissinica (p < 0.05). Nine functional groups, including seven carbon-related biogeochemical groups, were identified through the FAPROTAX analysis. However, the most dominant groups for G. haimaensis and A. marissinica were both chemoheterotrophic. G. haimaensis and A. marissinica shared many pathways, however, 16 obtained Kyoto Encyclopedia of Genes and Genomes (KEGG) orthologous groups (42.11%) significantly differed between the two species (p < 0.05). These findings would provide insight into the functions of microbes in the element cycling and energy flow as well as the host-symbiont relationship of bivalves in the Haima cold seep environment.

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