9:00 AM - 9:15 AM
[MIS21-01] Geochemical and molecular biological characterization of nitrogen dynamics in (hado)pelagic sediments
Great progress has been made in understanding the nitrogen cycle in oceanic waters by the recent identification of ammonia-oxidizing archaea and anaerobic ammonia oxidizer (anammox), and by the following comprehensive approaches to clarify the abundance and activity of each component in the nitrogen cycle. However, nitrogen dynamics in marine sedimentary habitats is still uncertain. To further characterize nitrogen dynamics in the deep-sea sediments, we have quantified i) gene abundance of putative nitrifers, denitrifers and anammox, and ii) potential rate of denitrification in the hadopelagic sediment cores taken from the Ogasawara Trench (water depth of 9760m). We have also determined nitrogen and oxygen stable isotopic compositions of nitrate in the interstitial water in the hadopelagic sediments. Abundance of potential proteobacterial denitrifers correlated with that of nitrifers through the depth, and anammox also likely co-occurred with nitrifers. Further, nitrate isotope compositions suggest the enrichment of 18O by nitrification process and co-occurrence of nitrification and denitrification in nitrate reduction zone. The data suggest that aerobic and anaerobic processes of the nitrogen cycle coupled in the nitrate reduction zone in the hadopelagic sediments.