scholarly journals Distinct Bottom-Water Bacterial Communities at Methane Seeps With Various Seepage Intensities in Haima, South China Sea

2021 ◽  
Vol 8 ◽  
Author(s):  
Xiaopeng Li ◽  
Zehan Dai ◽  
Pengfei Di ◽  
Junxi Feng ◽  
Jun Tao ◽  
...  
Keyword(s):  
South China Sea ◽  
Bacterial Community ◽  
Water Column ◽  
South China ◽  
Bottom Water ◽  
Methane Content ◽  
Cold Seeps ◽  
Community Structures ◽  
Methane Seeps ◽  
China Sea

Methane seeps are chemosynthetic ecosystems in the deep-sea environment. Microbial community structures have been extensively studied in the seepage-affected sediments and investigation in the water column above the seeping sites is still lacking. In this study, prokaryotic communities in the bottom water about 50 cm from the seabed at methane seeps with various seepage intensities in Haima, South China Sea were comparatively studied by using 16S ribosomal RNA gene sequencing. These sites were assigned based on their distinct methane content levels and seafloor landscapes as the non-seepage (NS) site, low-intensity seepage (LIS) site, and high-intensity seepage (HIS) site. The abundances of the dominant phyla Proteobacteria, Bacteroidetes, and Actinobacteria differed significantly between NS and the two seepage sites (p < 0.05). Alpha diversity differed among the three sites with the HIS site showing the lowest community diversity. Principal component analysis revealed highly divergent bacterial community structures at three sites. Many environmental variables including temperature, alkalinity, pH, methane, dissolved organic carbon (DOC), and inorganic nutrients were measured. Redundancy analysis indicated that methane content is the key environmental factor driving bacterial community variation (p = 0.001). Linear discriminant analysis effect size analysis identified various differentially enriched genera at the LIS and HIS sites. Phylogenetic analysis revealed close phylogenetic relationship among the operational taxonomic units of these genera with known oil-degrading species, indicating oil seepage may occur at the Haima cold seeps. Co-occurrence networks indicated that the strength of microbial interactions was weakest at the HIS site. This study represents a comprehensive comparison of microbial profiles in the water column of cold seeps in the SCS, revealing that the seepage intensity has a strong impact on bacterial community dynamics.

scholarly journals A Quantitative Assessment of Methane-Derived Carbon Cycling at the Cold Seeps in the Northwestern South China Sea

Minerals ◽  
2020 ◽  
Vol 10 (3) ◽  
pp. 256 ◽  
Author(s):  
Junxi Feng ◽  
Niu Li ◽  
Min Luo ◽  
Jinqiang Liang ◽  
Shengxiong Yang ◽  
...  
Keyword(s):  
South China Sea ◽  
South China ◽  
Bottom Water ◽  
Cold Seep ◽  
Anaerobic Oxidation Of Methane ◽  
Cold Seeps ◽  
Dissolved Carbon ◽  
China Sea ◽  
Seafloor Observation ◽  
Gas Hydrate Formation

Widespread cold seeps along continental margins are significant sources of dissolved carbon to the ocean water. However, little is known about the methane turnovers and possible impact of seepage on the bottom seawater at the cold seeps in the South China Sea (SCS). We present seafloor observation and porewater data of six push cores, one piston core and three boreholes as well as fifteen bottom-water samples collected from four cold seep areas in the northwestern SCS. The depths of the sulfate–methane transition zone (SMTZ) are generally shallow, ranging from ~7 to <0.5 mbsf (meters below seafloor). Reaction-transport modelling results show that methane dynamics were highly variable due to the transport and dissolution of ascending gas. Dissolved methane is predominantly consumed by anaerobic oxidation of methane (AOM) at the SMTZ and trapped by gas hydrate formation below it, with depth-integrated AOM rates ranging from 59.0 and 591 mmol m−2 yr−1. The δ13C and Δ14C values of bottom-water dissolved inorganic carbon (DIC) suggest discharge of 13C- and 14C-depleted fossil carbon to the bottom water at the cold seep areas. Based on a two-endmember estimate, cold seeps fluids likely contribute 16–26% of the bottom seawater DIC and may have an impact on the long-term deep-sea carbon cycle. Our results reveal the methane-related carbon inventories are highly heterogeneous in the cold seep systems, which are probably dependent on the distances of the sampling sites to the seepage center. To our knowledge, this is the first quantitative study on the contribution of cold seep fluids to the bottom-water carbon reservoir of the SCS, and might help to understand the dynamics and the environmental impact of hydrocarbon seep in the SCS.

Bacterial community variations in the South China Sea driven by different chemical conditions

Ecotoxicology ◽  
2021 ◽  
Author(s):  
Fu-lin Sun ◽  
You-Shao Wang ◽  
Mei-Lin Wu ◽  
Cui-Ci Sun ◽  
Zhao-Yu Jiang ◽  
...  
Keyword(s):  
South China Sea ◽  
Bacterial Community ◽  
South China ◽  
The South China Sea ◽  
The South ◽  
China Sea ◽  
Chemical Conditions

scholarly journals Impact of the Kuroshio intrusion on the nutrient inventory in the upper northern South China Sea: insights from an isopycnal mixing model

2013 ◽  
Vol 10 (10) ◽  
pp. 6419-6432 ◽  
Author(s):  
C. Du ◽  
Z. Liu ◽  
M. Dai ◽  
S.-J. Kao ◽  
Z. Cao ◽  
...  
Keyword(s):  
South China Sea ◽  
Water Column ◽  
South China ◽  
Water Mass ◽  
Northern South China Sea ◽  
Mixing Model ◽  
Nutrient Concentrations ◽  
Kuroshio Intrusion ◽  
China Sea ◽  
The Kuroshio

Abstract. Based on four cruises covering a seasonal cycle in 2009–2011, we examined the impact of the Kuroshio intrusion, featured by extremely oligotrophic waters, on the nutrient inventory in the central northern South China Sea (NSCS). The nutrient inventory in the upper 100 m of the water column in the study area ranged from ∼200 to ∼290 mmol m−2 for N + N (nitrate plus nitrite), from ∼13 to ∼24 mmol m−2 for soluble reactive phosphate and from ∼210 to ∼430 mmol m−2 for silicic acid. The nutrient inventory showed a clear seasonal pattern with the highest value appearing in summer, while the N + N inventory in spring and winter had a reduction of ∼13 and ∼30%, respectively, relative to that in summer. To quantify the extent of the Kuroshio intrusion, an isopycnal mixing model was adopted to derive the proportional contribution of water masses from the SCS proper and the Kuroshio along individual isopycnal surfaces. The derived mixing ratio along the isopycnal plane was then employed to predict the genuine gradients of nutrients under the assumption of no biogeochemical alteration. These predicted nutrient concentrations, denoted as Nm, are solely determined by water mass mixing. Results showed that the nutrient inventory in the upper 100 m of the NSCS was overall negatively correlated to the Kuroshio water fraction, suggesting that the Kuroshio intrusion significantly influenced the nutrient distribution in the SCS and its seasonal variation. The difference between the observed nutrient concentrations and their corresponding Nm allowed us to further quantify the nutrient removal/addition associated with the biogeochemical processes on top of the water mass mixing. We revealed that the nutrients in the upper 100 m of the water column had a net consumption in both winter and spring but a net addition in fall.

Constraining barium isotope fractionation in the upper water column of the South China Sea

2020 ◽  
Vol 288 ◽  
pp. 120-137
Author(s):  
Zhimian Cao ◽  
Yating Li ◽  
Xinting Rao ◽  
Yang Yu ◽  
Ed C. Hathorne ◽  
...  
Keyword(s):  
South China Sea ◽  
Water Column ◽  
South China ◽  
Isotope Fractionation ◽  
The South China Sea ◽  
The South ◽  
China Sea ◽  
Barium Isotope

6. Ecosystems of cold seeps in the South China Sea

2017 ◽  
Author(s):  
Mingyang Niu ◽  
Qianyong Liang ◽  
Dong Feng ◽  
Fengping Wang
Keyword(s):  
South China Sea ◽  
South China ◽  
The South China Sea ◽  
Cold Seeps ◽  
The South ◽  
China Sea

Multi-beam and seismic investigations of the active Haima cold seeps, northwestern South China Sea

2021 ◽  
Vol 40 (7) ◽  
pp. 183-197
Author(s):  
Bin Liu ◽  
Jiangxin Chen ◽  
Li Yang ◽  
Minliang Duan ◽  
Shengxuan Liu ◽  
...  
Keyword(s):  
South China Sea ◽  
South China ◽  
Cold Seeps ◽  
China Sea

scholarly journals Seasonal distributions and fluxes of <sup>210</sup>Pb and <sup>210</sup>Po in the northern South China Sea

2014 ◽  
Vol 11 (23) ◽  
pp. 6813-6826 ◽  
Author(s):  
C.-L. Wei ◽  
M.-C. Yi ◽  
S.-Y. Lin ◽  
L.-S. Wen ◽  
W.-H. Lee
Keyword(s):  
Time Series ◽  
South China Sea ◽  
Water Column ◽  
South China ◽  
Time Series Data ◽  
Northern South China Sea ◽  
Sediment Traps ◽  
Series Data ◽  
Secular Equilibrium ◽  
China Sea

Abstract. Vertical distributions of dissolved and particulate 210Pb and 210Po in the water column at the SouthEast Asian Time-series Study (SEATS, 18°00´ N and 116°00´ E) station in the northern South China Sea were determined from four cruises between January 2007 and June 2008. A large deficiency of 210Pb, 379 ± 43 × 103 dpm m−2, from the secular equilibrium was found within the 3500 m water column. On the other hand, a smaller deficiency of 210Po, 100 ± 21 × 103 dpm m−2, relative to 210Pb was found in the water column. Time-series data showed insignificant temporal variability of the 210Pb and 210Po profiles. To balance these deficiencies, the removal fluxes for 210Pb and 210Po via particle settling ranging from 45 to 51 dpm m−2d−1 and from 481 to 567 dpm m−2d−1, respectively, are expected at 3500 m. The 210Pb removal flux is comparable with, whereas the 210Po removal flux is much higher than, the flux directly measured by moored sediment traps. The discrepancy between the modeled 210Po flux and the measured flux suggests that sporadic events that enhance 210Po removal via sinking ballast may occur in the water column at the site.

Sign in / Sign up

Export Citation Format

Share Document