BIOMARKERS AND BACTERIAL PROCESSES IN THE SEDIMENTS OF GAS SEEP SITE

Methane oxidizing archea (MOA) and sulfate reducing bacteria (SRB) are abundant in cold seep and hydrate sites, where dominant anaerobic oxidation of methane played an important role in the sea carbon cycle and microbial propagation. MOA oxidizes methane into HCO₃^- and SRB reduces SO₄^2- into HS^- at gas seep site, which is anaerobic, and microbes obtain energy here for living and growth. At least MOA consists of three colonies:ANME-1, ANME-2 and ANME-3, showed in biomarkers as isoprenoids and free isoprenoid hydrocarbons. There are two colonies of SRB,that is, Desulfosarcina and Desulfococcus. The typical biomarkers produced by SRB are Dialkyl glycerol diethers (DGDs) and fatty acids. All the biomarkers of cold seep sites have very low carbon isotopic compositions which are between -41.1‰~-95.6‰, indicating that the microbes get carbon from CH₄ and that there are activities of MOA and SRB in anaerobic gas seep sites.