{"id":10094,"date":"2016-11-15T20:45:22","date_gmt":"2016-11-15T20:45:22","guid":{"rendered":"https:\/\/www.darkenergybiosphere.org\/?post_type=publication&#038;p=10094"},"modified":"2016-11-15T20:45:22","modified_gmt":"2016-11-15T20:45:22","slug":"evidence-for-microbial-mediation-of-subseafloor-nitrogen-redox-processes-at-loihi-seamount-hawaii","status":"publish","type":"publication","link":"https:\/\/www.darkenergybiosphere.org\/publication\/evidence-for-microbial-mediation-of-subseafloor-nitrogen-redox-processes-at-loihi-seamount-hawaii\/","title":{"rendered":"Evidence for microbial mediation of subseafloor nitrogen redox processes at Loihi Seamount, Hawaii"},"content":{"rendered":"<p>The role of nitrogen cycling in submarine hydrothermal systems is far less studied than that of other biologically reactive elements such as sulfur and iron. In order to address this knowledge gap, we investigated nitrogen redox processes at Loihi Seamount, Hawaii, using a combination of biogeochemical and isotopic measurements, bioenergetic calculations and analysis of the prokaryotic community composition in venting fluids sampled during four cruises in 2006, 2008, 2009 and 2013. Concentrations of NH<sub>4<\/sub><sup>+<\/sup> were positively correlated to dissolved Si and negatively correlated to NO<sub>3<\/sub><sup>&#8211;<\/sup>+NO<sub>2<\/sub><sup>&#8211;<\/sup>, while NO<sub>2<\/sub><sup>&#8211;<\/sup> was not correlated to NO<sub>3<\/sub><sup>&#8211;<\/sup>+NO<sub>2<\/sub><sup>&#8211;<\/sup>, dissolved Si or NH<sub>4<\/sub><sup>+<\/sup>. This is indicative of hydrothermal input of NH<sub>4<\/sub><sup>+<\/sup> and biological mediation influencing NO<sub>2<\/sub><sup>&#8211;<\/sup>concentrations. The stable isotope ratios of NO<sub>3<\/sub><sup>&#8211;<\/sup> (\u03b4<sup>15<\/sup>N and \u03b4<sup>18<\/sup>O) was elevated with respect to background seawater, with \u03b4<sup>18<\/sup>O values exhibiting larger changes than corresponding \u03b4<sup>15<\/sup>N values, reflecting the occurrence of both production and reduction of NO<sub>3<\/sub><sup>&#8211;<\/sup> by an active microbial community. \u03b4<sup>15<\/sup>N-NH<sub>4<\/sub><sup>+<\/sup> values ranged from 0\u2030 to +16.7\u2030, suggesting fractionation during consumption and potentially N-fixation as well. Bioenergetic calculations reveal that several catabolic strategies involving the reduction of NO<sub>3<\/sub><sup>&#8211;<\/sup> and NO<sub>2<\/sub><sup>&#8211;<\/sup> coupled to sulfide and iron oxidation could provide energy to microbes in Loihi fluids, while 16S rRNA gene sequencing of Archaea and Bacteria in the fluids reveals groups known to participate in denitrification and N-fixation. Taken together, our data support the hypothesis that microbes are mediating N-based redox processes in venting hydrothermal fluids at Loihi Seamount.<\/p>\n","protected":false},"template":"","tags":[],"publication_type":[19],"_links":{"self":[{"href":"https:\/\/www.darkenergybiosphere.org\/wp-json\/wp\/v2\/publication\/10094"}],"collection":[{"href":"https:\/\/www.darkenergybiosphere.org\/wp-json\/wp\/v2\/publication"}],"about":[{"href":"https:\/\/www.darkenergybiosphere.org\/wp-json\/wp\/v2\/types\/publication"}],"wp:attachment":[{"href":"https:\/\/www.darkenergybiosphere.org\/wp-json\/wp\/v2\/media?parent=10094"}],"wp:term":[{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.darkenergybiosphere.org\/wp-json\/wp\/v2\/tags?post=10094"},{"taxonomy":"publication_type","embeddable":true,"href":"https:\/\/www.darkenergybiosphere.org\/wp-json\/wp\/v2\/publication_type?post=10094"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}