Microbial community changes along the active seepage site of one cold seep in the Red Sea.

Huiluo Cao,Weipeng Zhang,Pei-Yuan Qian,Yong Wang

doi:10.3389/fmicb.2015.00739

Abstract

The active seepage of the marine cold seeps could be a critical process for the exchange of energy between the submerged geosphere and the sea floor environment through organic-rich fluids, potentially even affecting surrounding microbial habitats. However, few studies have investigated the associated microbial community changes. In the present study, 16S rRNA genes were pyrosequenced to decipher changes in the microbial communities from the Thuwal seepage point in the Red Sea to nearby marine sediments in the brine pool, normal marine sediments and water, and benthic microbial mats. An unexpected number of reads from unclassified groups were detected in these habitats; however, the ecological functions of these groups remain unresolved. Furthermore, ammonia-oxidizing archaeal community structures were investigated using the ammonia monooxygenase subunit A (amoA) gene. Analysis of amoA showed that planktonic marine habitats, including seeps and marine water, hosted archaeal ammonia oxidizers that differed from those in microbial mats and marine sediments, suggesting modifications of the ammonia oxidizing archaeal (AOA) communities along the environmental gradient from active seepage sites to peripheral areas. Changes in the microbial community structure of AOA in different habitats (water vs. sediment) potentially correlated with changes in salinity and oxygen concentrations. Overall, the present results revealed for the first time unanticipated novel microbial groups and changes in the ammonia-oxidizing archaea in response to environmental gradients near the active seepages of a cold seep.

Highlights

Cold seeps mainly occur in geologically active and passive continental margins, and they transport dissolved and gaseous phase compounds to the ocean to sustain significant chemosynthetic biomass by providing bioactive reductants, sulfides, methane and hydrogen (Levin, 2005; Suess, 2010)
The results showed that the habitat type dictated the community structure, while the environmental gradient shaped the changes in the ammonia oxidizing archaea (AOA) community from the active seepage site to peripheral areas
Sampling and Environmental Parameter Measurements Field sampling was conducted in November 2011 in the Thuwal cold Seep II (22o16’N–38o53’E) via the remotely operated vehicle (ROV) Max Rover developed by Deep Sea Systems International (DSSI), USA, during the KAUST Red Sea exploration cruise (Figure 1)

Summary

Introduction

Cold seeps mainly occur in geologically active and passive continental margins, and they transport dissolved and gaseous phase compounds to the ocean to sustain significant chemosynthetic biomass by providing bioactive reductants, sulfides, methane and hydrogen (Levin, 2005; Suess, 2010). A reduced diversity and abundance of the ammonia oxidizing archaea (AOA) thaumarchaea were found in cold seep sediments in the Okhotsk Sea (Dang et al, 2010) and northeastern Japan Sea (Nakagawa et al, 2007). All of these studies have shed some light on the possible contributions of various types of microorganisms to nitrogenous nutrient recycling; the ecological functions of the thaumarchaea in cold seeps remain largely unresolved

Methods

Results

Conclusion