Nature Geoscience contents: September 2013 Volume 6 Number 9 pp673-800

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Some background on our reasons for providing the option for authors to remain anonymous can be found in a Nature Geoscience Editorial. We also offer a checklist to help authors with anonymising their papers.   Insight Top Nature Geoscience Insight – Marine cycles in flux Insight issue: September 2013 Volume 6 No 9 Table of Contents Microbes regulate the cycling of elements throughout the global ocean, from the icy surface waters that circulate at high latitudes, to the deep vents that dot the continental sea floor. Human activities are starting to modify the way in which microbes mediate these cycles, at least in the relatively well-characterized waters of the upper ocean. The deeper layers of the ocean are probably less affected, at least at present, and are definitely less well explored. However, technological advances are starting to shed light on the cycling of elements at depth, revealing microbial systems that are quite different from those at the surface. In this Nature Geoscience Insight we highlight some of the most intriguing advances in the microbial biogeochemistry of the oceans, a field that is very much in flux. Editorials Top Landscape of the lost giants   p673 doi:10.1038/ngeo1945 The Pleistocene megafauna extinction erased a group of remarkable animals. Whether humans had a prominent role in the extinction remains controversial, but it is emerging that the disappearance of the giants has markedly affected the environment. Nature Geoscience Insight – Marine cycles in flux Marine cycles in flux   p687 Anna Armstrong doi:10.1038/ngeo1946 Correspondence Top Permafrost-carbon complexities   pp675 - 676 Jorien E. Vonk & Örjan Gustafsson doi:10.1038/ngeo1937 Commentary Top Nature Geoscience Insight – Marine cycles in flux Where the genes flow   pp688 - 690 Frank J. Stewart doi:10.1038/ngeo1939 Particles of organic matter in the ocean host diverse communities of microorganisms. These particles may serve as hotspots of bacterial gene exchange, creating opportunities for microbial evolution. In the press Top A river ran through it   p677 Emily Lakdawalla doi:10.1038/ngeo1935 Research Highlights Top Planetary science: Titan's evaporites | Volcanology: Glacial magma | Palaeoclimate: Snowball synchroneity | Atmospheric climate: Ozone-induced extremes News and Views Top Palaeoecology: Megafauna as a nutrient pump   pp679 - 680 Tanguy Daufresne doi:10.1038/ngeo1932 The end of the Pleistocene epoch saw the extinction of large-bodied herbivores around the world. Numerical modelling suggests that continental-scale effects of this extinction on nutrient transport are ongoing. See also: Letter by Doughty et al. Palaeoclimate: East Antarctica's Achilles' heel   pp680 - 681 Claus-Dieter Hillenbrand doi:10.1038/ngeo1897 The East Antarctic ice sheet is believed to be Earth's most stable ice sheet. Changes in geochemical composition of offshore sediments suggest that its margin repeatedly retreated by at least 350–550 kilometres inland between 5.3 and 3.3 million years ago. See also: Letter by Cook et al. Rivers: Building bacterial bridges   pp682 - 683 Aaron Packman doi:10.1038/ngeo1938 The classical view of fluvial sediment transport considers only physical interactions between the river flow and riverbed particles. Experiments and theory suggest that microbial biofilms reduce sediment mobility by binding many grains together. See also: Letter by Vignaga et al. Solid Earth: Heating glaciers from below   pp683 - 684 Boris J. P. Kaus doi:10.1038/ngeo1919 Climate change is affecting the cryosphere from above. Geothermal heat flux from below is also contributing to conditions at the base of Greenland's ice sheet, which sits atop a lithosphere of variable thickness. See also: Letter by Petrunin et al. Geoscience JOBS of the week Full Professor in "Organic Geochemistry", Tenured The Institute for Chemistry and Biology of the Marine Environment (ICBM) Assistant Professor (Tenure Track) of Experimental Geochemistry / Mineral Physics ETH Chair in Environmental Radiochemistry University of Southampton More Science jobs from Reviews Top Nature Geoscience Insight – Marine cycles in flux Impact of Arctic meltdown on the microbial cycling of sulphur   pp691 - 700 M. Levasseur doi:10.1038/ngeo1910 The Arctic is warming faster than any other region in the world. The resultant large-scale shift in sea ice cover could increase oceanic emissions of dimethylsulphide, a climate-relevant trace gas generated by ice algae and phytoplankton. Nature Geoscience Insight – Marine cycles in flux Processes and patterns of oceanic nutrient limitation   pp701 - 710 C. M. Moore, M. M. Mills, K. R. Arrigo, I. Berman-Frank, L. Bopp et al. doi:10.1038/ngeo1765 Photosynthetic microbes, collectively termed phytoplankton, are responsible for the vast majority of primary production in marine waters. A synthesis of the latest research suggests that two broad nutrient limitation regimes — characterized by nitrogen and iron limitation, respectively — dictate phytoplankton abundance and activity in the global ocean. Nature Geoscience Insight – Marine cycles in flux Microbial biogeochemistry of coastal upwelling regimes in a changing ocean   pp711 - 717 Douglas G. Capone & David A. Hutchins doi:10.1038/ngeo1916 Coastal upwelling regimes associated with eastern boundary currents are the most biologically productive ecosystems in the ocean. A suite of human-induced changes, including ocean acidification and warming, an intensification of hypoxia, stratification-driven changes in nutrient and light supplies, and changes in atmospheric iron and nitrogen deposition, could peturb primary production and nutrient dynamics in these systems. Nature Geoscience Insight – Marine cycles in flux Microbial control of the dark end of the biological pump   pp718 - 724 Gerhard J. Herndl & Thomas Reinthaler doi:10.1038/ngeo1921 The flux of carbon out of the ocean surface is not sufficient to meet the energy demands of microbes in the dark ocean. A review of the literature suggests that non-sinking particles and microbes that convert inorganic carbon into organic matter could help to meet this deep-ocean energy demand. Nature Geoscience Insight – Marine cycles in flux Seafloor oxygen consumption fuelled by methane from cold seeps   pp725 - 734 Antje Boetius & Frank Wenzhöfer doi:10.1038/ngeo1926 The leakage of cold, methane-rich fluids from subsurface reservoirs to the sea floor sustains some of the richest ecosystems on the sea bed. These cold-seep communities consume around two orders of magnitude more oxygen than the surrounding sea floor, as a result of the microbial consumption of seep methane. Letters Top Remote detection of magmatic water in Bullialdus Crater on the Moon   pp737 - 741 R. Klima, J. Cahill, J. Hagerty & D. Lawrence doi:10.1038/ngeo1909 The remote detection of surface water indigenous to the Moon has proved difficult because of alternative sources, such as the solar wind. Spectroscopic observations of hydroxyl-bearing materials in Bullialdus Crater by the Chandrayaan-1 spacecraft are consistent with indigenous magmatic water that was excavated by impact from the lunar interior. Rising river flows throughout the twenty-first century in two Himalayan glacierized watersheds   pp742 - 745 W. W. Immerzeel, F. Pellicciotti & M. F. P. Bierkens doi:10.1038/ngeo1896 Greater Himalayan glaciers are retreating and losing mass. A combination of the latest ensemble of climate models combined with a glacio-hydrological model suggests that in two contrasting watersheds in the Greater Himalaya, glaciers will recede but net glacier melt runoff is on a rising limb until at least 2050. Heat flux variations beneath central Greenland's ice due to anomalously thin lithosphere   pp746 - 750 A. G. Petrunin, I. Rogozhina, A. P. M. Vaughan, I. T. Kukkonen, M. K. Kaban et al. doi:10.1038/ngeo1898 The thermal state of the Earth's surface is usually influenced more by climate than by heating from the Earth's interior. Numerical models show that in the oldest and thickest part of the Greenland Ice Sheet, geothermal heat flux through an anomalously thin lithosphere leads to strong regional variations in basal melting. See also: News and Views by Kaus Oxidation and methylation of dissolved elemental mercury by anaerobic bacteria   pp751 - 754 Haiyan Hu, Hui Lin, Wang Zheng, Stephen J. Tomanicek, Alexander Johs et al. doi:10.1038/ngeo1894 Methylmercury is a neurotoxin that poses significant health risks to humans. Laboratory experiments suggest that the activity of methylating and non-methylating bacteria may together enhance the formation of methylmercury in anaerobic environments. Formation of carbonate chimneys in the Mediterranean Sea linked to deep-water oxygen depletion   pp755 - 760 Germain Bayon, Stéphanie Dupré, Emmanuel Ponzevera, Jöel Etoubleau, Sandrine Chéron et al. doi:10.1038/ngeo1888 Submarine seeps release substantial amounts of methane into the overlying water column at continental margins, leading to the formation of calcium carbonate deposits. Analyses of methane-derived carbonate build-ups on the Nile Delta suggest that their formation coincided with the development of deep-water anoxic or suboxic conditions. The legacy of the Pleistocene megafauna extinctions on nutrient availability in Amazonia   pp761 - 764 Christopher E. Doughty, Adam Wolf & Yadvinder Malhi doi:10.1038/ngeo1895 Between about 50 and 10 thousand years ago, almost 100 genera of large animals went extinct. Mathematical analyses suggest that the extinctions in Amazonia have led to a reduction in the lateral flux of the limiting nutrient phosphorus—by transport of dung and bodies—by 98%. See also: News and Views by Daufresne Dynamic behaviour of the East Antarctic ice sheet during Pliocene warmth   pp765 - 769 Carys P. Cook, Tina van de Flierdt, Trevor Williams, Sidney R. Hemming, Masao Iwai et al. doi:10.1038/ngeo1889 The East Antarctic ice sheet is considered to be largely insensitive to temperature changes in the Southern Ocean. Marine sediment records indicate the East Antarctic ice sheet repeatedly retreated by several hundred kilometres during intervals of Pliocene warmth. See also: News and Views by Hillenbrand Erosion of biofilm-bound fluvial sediments   pp770 - 774 Elisa Vignaga, David M. Sloan, Xiaoyu Luo, Heather Haynes, Vernon R. Phoenix et al. doi:10.1038/ngeo1891 Sediment grains in rivers are often bound together and stabilized by bacterial films. Experiments and mathematical models show that sediments bound by biofilms behave like a single elastic membrane that can rip catastrophically if the river flows fast enough. See also: News and Views by Packman Slow-spreading submarine ridges in the South Atlantic as a significant oceanic iron source   pp775 - 779 Mak A. Saito, Abigail E. Noble, Alessandro Tagliabue, Tyler J. Goepfert, Carl H. Lamborg et al. doi:10.1038/ngeo1893 Low levels of the micronutrient iron limit primary production and nitrogen fixation in large areas of the global ocean. Measurements in the South Atlantic suggest that slow-spreading submarine ridges serve as a significant oceanic iron source in these waters. The proportionality between relative plate velocity and seismicity in subduction zones   pp780 - 784 Satoshi Ide doi:10.1038/ngeo1901 The magnitude and rate of seismicity differ between subduction zones. Calculations of background seismicity rates, based on a global model of subduction zone seismicity, reveal a positive correlation between relative plate velocity and background seismicity, yet only the seismically quieter zones seem capable of generating magnitude 9 earthquakes. Structure of orogenic belts controlled by lithosphere age   pp785 - 789 Frédéric Mouthereau, Anthony B. Watts & Evgueni Burov doi:10.1038/ngeo1902 The influence of inherited tectonic-plate strength on the structure of mountain belts is debated. Analysis of geological data collected from mountain belts worldwide shows that the style and amount of deformation in a mountain range are strongly influenced by the age and strength of the colliding plates. Articles Top Taxon-specific response of marine nitrogen fixers to elevated carbon dioxide concentrations   pp790 - 795 David A. Hutchins, Fei-Xue Fu, Eric A. Webb, Nathan Walworth & Alessandro Tagliabue doi:10.1038/ngeo1858 Marine cyanobacteria supply much of the nitrogen that supports open ocean food webs and biogeochemical cycles. An experimental study suggests that the relationship between nitrogen fixation and carbon dioxide concentration varies significantly between cyanobacterial strains. Ice sheet collapse following a prolonged period of stable sea level during the last interglacial   pp796 - 800 Michael J. O'Leary, Paul J. Hearty, William G. Thompson, Maureen E. Raymo, Jerry X. Mitrovica et al. doi:10.1038/ngeo1890 Sea level during the last interglacial period reached a peak of between 5 and 9 m above the present-day level. A detailed reconstruction of sea level and isostatic rebound from Western Australia indicates a prolonged period of sea-level stability at 3–4 m above present, followed by an abrupt sea-level rise of 5–6 m. Top Advertisement The NatureJournals app  Download the NatureJournals app for iPhone, iPad and iPod touch. Tap in and subscribe to Nature Geoscience via the app for just $49.99*  *Apple exchange rates apply iPhone, iPad and iPad touch are trademarks of Apple Inc   Natureevents is a fully searchable, multi-disciplinary database designed to maximise exposure for events organisers. The contents of the Natureevents Directory are now live. The digital version is available here. Find the latest scientific conferences, courses, meetings and symposia on natureevents.com. For event advertising opportunities across the Nature Publishing Group portfolio please contact natureevents@nature.com More Nature Events

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