Research On The Anammox Bacteria Retrieved From The Deep-sea Sediments Of The Northern South China Sea And Okhotsk Sea

The South China Sea and the Okhotsk Sea are both marginal sea located in the Western Pacific Ocean, harbors one of the largest reservoirs of methane hydrates and prospect area in the world, respectively. Marginal sea methane seep sediments, are hotspots for rapid biogeochemical cycling and sustain highly productive chemosynthetic ecosystems. The anaerobic ammonium oxidation (anammox, NH4++NO2-â†'N2+2H2O) process removes fixed nitrogen and produces N2in anoxic environments. In some regions of the world’s oceans, more than50%of N2production in marine sediments and oxygen-depleted zones of seawater may be attributed to anammox, thus, it is an important process in marine biogeochemical nitrogen cycle. Moreover, it is anticipated that Anammox process might also affect the concentration of CO2in the atmosphere, influence the global climate change and and provide a much more effective biotechnological process. To test the hypothesis that these hypoxic sediments sustain diverse and abundant anaerobic ammonium oxidation (anammox) bacteria in the South China Sea and Okhotsk Sea, we employed detection of both16S rRNA and hzo (encoding hydrazine oxidoreductase) genes to investigate the structure, abundance and distribution of the anammox bacterial community.Diverse complements of Candidates Scalindua-related16S rRNA and hzo gene sequences were obtained and most of the sites harbored abundant anammox bacterial hzo gene copies with copy numbers as high as107g-1sediment. In general, anammox bacterial signatures were significantly more abundant in the deep-water sediments. Sediment porewater NO2-, NO3-, NOx-(NO3-plus NO2-), OrgN, OrgP, temperature and sediment silt content correlated with in situ anammox bacterial distribution patterns, likely because they determine anammox substrate availability and sediment geochemistry, respectively. Besides sediment silt content, some other sedimentological parameters were also found to correlate with anammox bacterial marker abundance in the two marginal seas which may be related to sediment silt content. Diversity, abundance and distribution of anammox bacterial markers indicate the potentially significant contribution of anammox bacteria to the marine N cycle in the South China Sea and the Okhotsk Sea.