Methanogenesis and anaerobic oxidation of methane driven by microbial activites are important for the global methane cycle.Marine gas hydrate is a huge methane reservoir on Earth

however

it remains unclear whether archaeal community structure in marine sediments can indicate marine gas hydrate.In this study

distinct archaeal communities thriving in marine sediments of core 973-3 in southwestern Taiwan Basin of the northern South China Sea were characte-rized by 16S rDNA gene analysis.Moreover

we discussed the effect of diagenetic environment factors on archaeal community distributions.Results show that Methanosaeta is the most abundant in 20~450 cm depths

with 32.9% proportion.Methanosarcinales dominates in 542-870cm depths with 28.3% proportion

while Methanomicrobiales is predominant in 1 075-1 162cm depths with 20.7% proportion.The archaeal community structure in core 973-3 is closely related to the methanogenesis and methane oxidation

indicating the presence of gas hydrate.The variations of diagenetic environment parameters are responding to the gas hydrate formation.The pH values increase with depth

contrary to E

h

salinity and grain sizes.It is obviously different of archaeal communities in core 973-3

compared to that in gas hydrate-containing and -free sediments from Japan Sea and the Shenhu area of South China Sea

owing to the significant effects of pH

E

h

and grain sizes on the distributions of archaeal community in core 973-3.Hence

it is essential to focus on the main niche for the methanogens and methanotrophs

to improve archaeal communities indicating marine gas hydrate.