Changes of carbon to nitrogen ratio in particulate organic matter in the marine mesopelagic zone: A case from the South China Sea

Fe and Mn oxides and (oxy)-hydroxides are the most abundant solid-phase electron acceptors in marine sediments, and dissimilatory Fe/Mn reduction usually links with the anaerobic oxidation of methane (AOM) and organic matter oxidation (OMO) in sediments. In this study, we report the results from subsurface marine sediments in the Dongsha hydrate-bearing area in the South China Sea. The petrological and geochemical signatures show that the Fe/Mn reduction mediated by AOM and OMO might occur in sediments above the sulfate-methane transition zone. X-ray diffraction and scanning electron microscopy analyses of sediments indicate that Fe(III)/Mn(IV)-oxides and authigenic carbonate minerals coexisted in the Fe/Mn reduction zone. The lower δ13C values of dissolved inorganic carbon, coupled with an evident increase in total inorganic carbon contents and a decrease in Ca2+ and Mg2+ concentrations indicate the onset of AOM in this zone, and the greater variation of PO43− and NH4+ concentrations in pore water suggests the higher OMO rates in subsurface sediments. Geochemical and mineralogical analyses suggest that the previously buried Fe(III)/Mn(IV) oxides might be activated and lead to the onset of Fe/Mn reduction induced by AOM and OMO. These findings may extend our understanding of the biogeochemical processes involved in Fe/Mn reduction in continental shelves with abundant methane, organic matter, and terrigenous metal oxides.

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Composition of the organic matter of the water, suspended matter, and bottom sediments in Nha Trang Bay in Vietnam in the South China Sea

Oceanology ◽

10.1134/s0001437011060130 ◽

2011 ◽

Vol 51 (6) ◽

pp. 959-968 ◽

Cited By ~ 2

Author(s):

V. I. Peresypkin ◽

A. V. Smurov ◽

N. A. Shulga ◽

E. S. Safonova ◽

T. G. Smurova ◽

...

Keyword(s):

Organic Matter ◽

South China Sea ◽

Bottom Sediments ◽

South China ◽

Suspended Matter ◽

The South China Sea ◽

The South ◽

China Sea ◽

Nha Trang Bay

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Unchanged nitrogen isotopic composition of organic matter in the South China Sea during the last climatic cycle: Global implications

Paleoceanography ◽

10.1029/1999pa000407 ◽

2000 ◽

Vol 15 (2) ◽

pp. 244-253 ◽

Cited By ~ 83

Author(s):

Markus Kienast

Keyword(s):

Organic Matter ◽

South China Sea ◽

Isotopic Composition ◽

South China ◽

The South China Sea ◽

The South ◽

China Sea ◽

Climatic Cycle ◽

Nitrogen Isotopic Composition

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Metaproteomic characterization of dissolved organic matter in the water column of the South China Sea

Limnology and Oceanography ◽

10.4319/lo.2011.56.5.1641 ◽

2011 ◽

Vol 56 (5) ◽

pp. 1641-1652 ◽

Cited By ~ 17

Author(s):

Da-Zhi Wang ◽

Hong-Po Dong ◽

Zhang-Xian Xie ◽

Min-Han Dai ◽

Hua-Sheng Hong

Keyword(s):

Organic Matter ◽

South China Sea ◽

Dissolved Organic Matter ◽

Water Column ◽

South China ◽

The South China Sea ◽

The South ◽

China Sea

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Climatic or tectonic control on organic matter deposition in the South China Sea? A lesson learned from a comprehensive Neogene palynological study of IODP Site U1433

International Journal of Coal Geology ◽

10.1016/j.coal.2017.10.003 ◽

2018 ◽

Vol 190 ◽

pp. 166-177 ◽

Cited By ~ 2

Author(s):

Yunfa Miao ◽

Sophie Warny ◽

Peter D. Clift ◽

Mitch Gregory ◽

Chang Liu

Keyword(s):

Organic Matter ◽

South China Sea ◽

South China ◽

The South China Sea ◽

The South ◽

Tectonic Control ◽

China Sea ◽

Palynological Study

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Source Indication and Geochemical Significance of Sedimentary Organic Matters from the Xisha Area, the South China Sea

Molecules ◽

10.3390/molecules26226808 ◽

2021 ◽

Vol 26 (22) ◽

pp. 6808

Author(s):

Yan Li ◽

Qian-Zhi Zhou ◽

Xiang-Po Xu ◽

Yun-Xin Fang ◽

Jin-Zhong Liu ◽

...

Keyword(s):

Organic Matter ◽

South China Sea ◽

South China ◽

Complex Mixture ◽

Petroleum Reservoirs ◽

The South China Sea ◽

Molecular Evidence ◽

The South ◽

Δ13c And Δ15n ◽

China Sea

Although various geochemical and geophysical investigations have already indicated a great resource potential in the Xisha area of the South China Sea, the origin of organic matter and molecular evidence for tracing the migration of hydrocarbons from deep petroleum reservoirs are still lacking. In this study, systematic organic geochemical analyses, including bulk organic matter parameters and lipid biomarkers were performed for deep sediments from two cores. The C/N ratios and δ13C and δ15N values of organic matter in most of the samples, together with the maxima of short-chain n-alkanoic acids and mid-chain n-alkanols, high abundances of monounsaturated fatty acids C18:1ω9 and C22:1ω13, jointly indicate the dominance of marine organic matter. n-Alkanes in sediments from core GMGS4-XH-W06B are characterized by small unresolved complex mixture (UCMs) humps, high odd/even predominance (OEP) and carbon preference index (CPI) values, clearly exhibiting characteristics of modern sediments. However, the sediments for core GMGS4-XH-W03B are featured with big UCMs, associated with OEP and CPI values around 1.0, showing signatures of petroleum hydrocarbons from high maturity sources. Considering the geologic background, the biomarker signatures are solid evidence for indicating the existence of underlying petroleum reservoirs, and may provide the valuable information for assessing the hydrocarbon resources in the Xisha area.

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