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

Hongpeng Cui,Xin Su,Jinlian Wang,Shiping Wei,Sihai Chen,Fang Chen

doi:10.14393/bj-v32n4a2016-33994

Abstract

Jiulong methane reef, a large cold seep area on the continental slope of the South China Sea (SCS), was characterized by chemosynthetic fauna, bacterial mats, methane-derived carbonate structures, and a shallow depth of sulfate-methane transition zone (SMTZ) in gravity cores. To characterize the microbial diversity and variation in correlation to methane venting in the cold seep area, the archaeal community in sediments of the gravity Core CL11 was analyzed, using the Illumina MiSeq sequencing system. A total of 96,917 valid sequences were obtained and classified into 275 OTUs. Taxonomic analysis showed that all the archaeal sequences belonged to the phyla of Crenarchaeota (69.41%) and Eurarchaeota (25.26%). Vertical distribution of the archaeal communities showed that the Marine Benthic Group B (MBG-B) was the predominant group (58.92%) in the topmost sediment of the core, while percentages of the South African Gold Mine Euryarchaeotal Group (SAGMEG) sequences increased with depth. Our findings indicate that the archaeal community in the cold seep of Jiulong Methane Reef is unique and provides us new insights into the archaeal community composition of the cold seep area.

Highlights

Cold seeps represent one of the most extreme marine conditions and are characterized by fluids seepage into surface sediments, causing elevated methane and/or sulfide concentrations over those of ambient seawater, forming oases of elevated microbial biomass and various faunal assemblages on the seafloor
Phylogenetic analysis of archaeal community revealed that anaerobic methane oxidation group (ANMEs) and MBG-D were detected at Hydrate Ridge (KNITTEL et al 2005), whereas the archaeal phylotypes were mainly composed of Marine Group I (MGI), Miscellaneous Crenarchaeotic Group (MCG) and MBG-B in the tropical Timor Sea methane seep (WASMUND et al 2009)
This result agrees with Patrick et al (2007), which found that sediment porosity for shallow and unconsolidated sediments is mainly correlated to abundances of sand and coarser silt, and to fractional-packing type of these coarse grains

Summary

Introduction

Cold seeps represent one of the most extreme marine conditions and are characterized by fluids seepage into surface sediments, causing elevated methane and/or sulfide concentrations over those of ambient seawater, forming oases of elevated microbial biomass and various faunal assemblages on the seafloor. Considerable research of archaeal communities has been conducted in different typological cold seep areas around the world, such as Hydrate Ridge (KNITTEL et al 2005), Nankai Trough (ARAKAWA et al 2006), Tropical Timor Sea (WASMUND et al 2009), Northern South China Sea (Northern SCS) (ZHANG et al 2012), and Sonora Margin (VIGNERON et al 2013). These studies showed that different cold seep areas harbored different archaeal communities. Even though high concentrations of methane and sulfate are available, the methanotrophic microbial activity and biomass

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Discussion

Conclusion