Microbial Diversity in the Deep Marine Sediments from the Qiongdongnan Basin in South China Sea

Abstract

The continental shelf and slope in the northern South China Sea is well known for its prospect of oil/gas/gas-hydrate resources. To study microbial communities and their roles in carbon cycling, a 4.9-m sediment core was collected from the Qiongdongnan Basin on the continental slope of the South China Sea during our cruise HY4-2005-5 in 2005. Geochemical, mineralogical, and molecular phylogenetic analyses were carried out. Sulfate concentration in pore water decreased with depth. Abundant authigenic carbonates and pyrite were observed in the sediments. The bacterial community was dominated by aerobic and facultative organisms. Bacterial clone sequences belonged to the Gamma-, Alpha-, Deltaproteobacteria and Firmicutes group, and they were related to Fe(III) and/or Mn(IV) reducers, sulfate reducers, aromatic hydrocarbon degraders, thiosulfate/sulfite oxidizers, and denitrifiers. Archaeal clone sequences exhibited greater overall diversity than the bacterial clones with most sequences related to Deep-Sea Archaeal Group (DSAG), Miscellaneous Crenarchaeotic Group (MCG), and Uncultured Euryarchaeotic Clusters (UECs). Archaeal sequences related to Methanosarcinales, South African Gold Mine Euryarchaeotic Group (SAGMEG), Marine Benthic Group-D (MBG-D) were also present. Most of these groups are commonly present in deep-sea sediments, particularly in methane/organicrich or putative methane hydrate-bearing sediments.

Vertical distribution of archaeal communities in cold seep sediments from the jiulong methane reef area in the south China sea

“…The microbial cellular abundance in sediments of Core CL11 was 10 7 cells/g, which was higher than both the 10 6 cells/g measured in abyssal (collected at about 3000 m water depth) cold seep sediment with 0.5% TOC of the northeastern SCS (ZHANG et al 2012). Our data is similar with the result from Qiongdongnan Basin, in which the cell number was 10 7 cells/g in sediments with 0.84 % to 1.2 % TOC (JIANG et al 2007). Downcore microbial cell abundance showed that relatively higher bacteria abundance was detected at depths of 350 cmbsf and 720 cmbsf, which is not consistent considering the TOC content.…”

“…Total cell number ranged from 10 8 to 10 9 cells/cm 3 in sediments near the surface, and declined with depth in the sediment column (D 'HONDT et al 2004), but showed variation with the different environments. The bacterial cell abundance was estimated to range from 10 5 -10 8 cells/g in sediments in continental slope or deep sea sediments from the SCS (ZHANG et al 2012;JIAO et al 2015;JIANG et al 2007). It was inferred that variations of microbial abundance in marine sediments might relate to concentrations of intact phospholipids and TOC (LIPP et al 2008).…”

Diversity of culturable bacteria in deep-sea water from the South Atlantic Ocean

“…The 17 water samples were dominated by populations of strains belonging to the class g-Proteobacteria (44.53%). The dominance of g-Proteobacteria sequences is commonly reported, and the same result has been found at many different locations, such as the Mid-Atlantic Ridge, 17 the North Atlantic, 18 the South China Sea, 19,20 the Pacific nodule province 21 and the Japan Trench. 22,23 Furthermore, their abundance was shown to increase with depth in the North Atlantic, 18 and our investigation obtained the same results at CTD 06 and CTD 10.…”

Tracing the life history of a marginal sea—On “The South China Sea Deep” Research Program

“…These pioneering works mostly devote to reporting microbial diversity in surface sediments [128][129][130][131][132], with only a few also including comparisons between microbial assemblages from different water depths [133] or discussions on a specific group of microbes such as alkane degrading bacteria [134]. Nevertheless, cold seepage studies have examined the role of chemosynthetic microbes in carbonate formation [119].…”