Glud, Ronnie N.7; Wenzhoefer, Frank3; Middelboe, Mathias4; Oguri, Kazumasa5; Turnewitsch, Robert6; Canfield, Donald Eugene8; Kitazato, Hiroshi5
1 Department of Biology, Faculty of Science, SDU2 Nordic Center for Earth Evolution (NordCEE), Department of Biology, Faculty of Science, SDU3 Max Planck Inst Marine Microbiol, D-28359 Bremen4 Univ Copenhagen, Marine Biol Sect, DK-3000 Helsingor5 Japan Agcy Marine Earth Sci & Technol, Inst Biogeosci, Yokosuka, Kanagawa 23700616 Scottish Assoc Marine Sci, Scottish Marine Inst, Oban PA37 1QA, Argyll7 Department of Biology, Faculty of Science, SDU8 Nordic Center for Earth Evolution (NordCEE), Department of Biology, Faculty of Science, SDU
Microbes control the decomposition of organic matter in marine sediments. Decomposition, in turn, contributes to oceanic nutrient regeneration and influences the preservation of organic carbon(1). Generally, rates of benthic decomposition decline with increasing water depth, although given the vast extent of the abyss, deep-sea sediments are quantitatively important for the global carbon cycle(2,3). However, the deepest regions of the ocean have remained virtually unexplored(4). Here, we present observations of microbial activity in sediments at Challenger Deep in the Mariana Trench in the central west Pacific, which at almost 11,000 m depth represents the deepest oceanic site on Earth. We used an autonomous micro-profiling system to assess benthic oxygen consumption rates. We show that although the presence of macrofauna is restricted at Challenger Deep, rates of biological consumption of oxygen are high, exceeding rates at a nearby 6,000-m-deep site by a factor of two. Consistently, analyses of sediments collected from the two sites reveal higher concentrations of microbial cells at Challenger Deep. Furthermore, analyses of sediment Pb-210 profiles reveal relatively high sediment deposition in the trench. We conclude that the elevated deposition of organic matter at Challenger Deep maintains intensified microbial activity at the extreme pressures that characterize this environment.
Nature Geoscience, 2013, Vol 6, Issue 4, p. 284-288