The depth of oxygen penetration into marine sediments differs considerably from one region to another. In areas with high rates of microbial respiration, O 2 penetrates only millimetres to centimetres into the sediments, but active anaerobic microbial communities are present in sediments hundreds of metres or more below the sea floor. In areas with low sedimentary respiration, O 2 penetrates much deeper but the depth to which microbial communities persist was previously unknown. The sediments underlying the South Pacific Gyre exhibit extremely low areal rates of respiration. Here we show that, in this region, microbial cells and aerobic respiration persist through the entire sediment sequence to depths of at least 75 metres below sea floor. Based on the Redfield stoichiometry of dissolved O 2 and nitrate, we suggest that net aerobic respiration in these sediments is coupled to oxidation of marine organic matter. We identify a relationship of O 2 penetration depth to sedimentation rate and sediment thickness. Extrapolating this relationship, we suggest that oxygen and aerobic communities may occur throughout the entire sediment sequence in 15-44% of the Pacific and 9-37% of the global sea floor. Subduction of the sediment and basalt from these regions is a source of oxidized material to the mantle.
Bibliographical noteFunding Information:
This research would not have been possible without the dedicated effort of the drilling crew, ship’s crew and scientific staff of the Drillship JOIDES Resolution. We thank the shipboard scientific party, coring crew and ship’s crew of piston-coring expedition KN223 for dedicated effort that allowed us to test our global O2 model in the North Atlantic. We thank V. M. Fulfer and M. J. Hayden for assistance with data compilation. The project was undertaken as part of Integrated Ocean Drilling Program (IODP) Expedition 329. The expedition was funded by the US National Science Foundation (NSF); the Ministry of Education, Culture, Sports, Science and Technology, Japan (MEXT); the European Consortium for Ocean Research Drilling; the Ministry of Science and Technology (People’s Republic of China); the Korea Institute of Geoscience and Mineral Resources; the Australian Research Council and the New Zealand Institute for Geological and Nuclear Sciences; and the Ministry of Earth Sciences (India). Post-expedition analyses were funded by the NSF Division of Ocean Sciences (grant 0939564 to S.D’H. and grant 1130735 to S.D’H. and A.J.S.), the Japan Society for the Promotion of Science (JSPS) Grants-in-Aid for Science Research (no. 26251041, 24651018, 24687004, and GR102 in the NEXT Program: to F.I. and Y.M.) through the MEXT, and the Deutsche Forschungsgemeinschaft (grant to J.Kallmeyer). Expedition KN223 was funded by the NSF Division of Ocean Sciences (grant 1433150 to A.J.S., S.D’H. and R.P.). This is a contribution to the Deep Carbon Observatory (DCO). It is Center for Dark Energy Biosphere Investigations (C-DEBI) publication 254.
All Science Journal Classification (ASJC) codes
- Earth and Planetary Sciences(all)