In situ Raman Quantitative Detection of the Cold Seep Vents and Fluids in the Chemosynthetic Communities in the South China Sea

Abstract

Based on the previously developed deep-sea hybrid Raman insertion probe for cold seeps, the in situ detection of a cold seep vent and geochemistry analysis of fluids in chemosynthetic communities were conducted at the Formosa Ridge in the northern South China Sea. Three different methods were used to measure the components of the fluids erupting from the cold seep vent. The in situ Raman spectra of the cold seep fluids indicated the presence of gaseous CH 4 , C 3 H 8 , and H 2 S. The results indicate that the gases at this site are of biogenic origin; however, the presence of C 3 H 8 suggests that thermogenic methane should not be excluded. The conclusion is also supported by the results of gas chromatography and stable carbon isotope analysis. More significantly, we found that the concentration of SO 4 2À decreases with increasing depth, while the concentrations of CH 4 and S 8 increase in fluids in chemosynthetic communities, but without H 2 S. This finding indicates that the methane is oxidized by sulfate and that elemental sulfur is formed. This process usually occurs in marine sediments as the anaerobic oxidation of methane. Overall, the findings in this work provide a new insight into the geochemical analysis of cold seep fluids and in situ evidence of the oxidation of methane in the chemosynthetic communities near cold seeps.

Metabolic diversification of anaerobic methanotrophic archaea in a deep-sea cold seep

“…The Jiaolong cold seep was active and the concentration of methane in sediments had been documented (0 cm: 0 mmol/L, 20 cm: 6.36 ± 0.11 mmol/L, 30 cm: 6.87 ± 0.33 mmol/L, 40 cm: 16.88 ± 0.33 mmol/L) in a previous study (Du et al 2018b). The δ 13 C values of CH 4 dissolved in seawater has also been measured (the δ 13 C values of two water samples: − 58.7‰ and − 61.1‰) (Feng Fig.…”

“…The Jiaolong cold seep, which was discovered in 2013, had developed a typical cold-seep ecosystem. In this area, the overflow of methane could be clearly detected by geochemical surveys and an in situ Raman spectrometry measurements (Du et al 2018b;Feng et al 2015). In a recent study, we reported on the structure of microbial communities and the distribution of functional genes of the core players in four subsurface sediment layers of the Jiaolong cold seep (Wu et al 2018).…”

A glimpse of deep‐sea adaptation in chemosynthetic holobionts: Depressurization causes DNA fragmentation and cell death of methanotrophic endosymbionts rather than their deep‐sea Bathymodiolinae host

“…The employment of these devices has provided unique opportunities to comprehensively reveal the biological processes of deep‐sea organisms. Very recently, an isobaric sampling device was manufactured by our laboratory and employed in the recovery of gas hydrates (Du et al, 2018). With some modifications, the sampler was used to capture and transfer Gigantidas mussels (Figure 1c).…”

Hydrothermal Vapor‐Phase Fluids on the Seafloor: Evidence From In Situ Observations

“…In this study, in situ Raman measurements were conducted using the Raman insertion probe (RiP) system (Movies S2) (Zhang, Du, Luan, et al, 2017; Zhang, Du, Zheng, et al, 2017), which has been successfully applied in the Manus Basin hydrothermal fields and cold seeps in the South China Sea (Du, Zhang, Luan, et al, 2018; Du, Zhang, Xi, et al, 2018; Li et al, 2018a; Xi et al, 2018; Zhang, Du, Luan, et al, 2017). The RiP system was developed on the basis of the Deep Ocean Raman In Situ Spectrometer (DORISS) (Brewer et al, 2004), and it inherits the main hardware components and spectral parameters of DORISS (Brewer et al, 2004; Zhang et al, 2010, 2012).…”