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Volume 2016 (2016), Article ID 2690329, 12 pages
Research Article

Marine Subsurface Microbial Community Shifts Across a Hydrothermal Gradient in Okinawa Trough Sediments

Department of Geosciences, The Pennsylvania State University, 220 Deike Building, University Park, PA 16802, USA

Received 9 June 2016; Revised 12 October 2016; Accepted 23 October 2016

Academic Editor: André Antunes

Copyright © 2016 Leah D. Brandt and Christopher H. House. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


Sediments within the Okinawa back-arc basin overlay a subsurface hydrothermal network, creating intense temperature gradients with sediment depth and potential limits for microbial diversity. We investigated taxonomic changes across 45 m of recovered core with a temperature gradient of 3°C/m from the dynamic Iheya North Hydrothermal System. The interval transitions sharply from low-temperature marine mud to hydrothermally altered clay at 10 meters below seafloor (mbsf). Here, we present taxonomic results from an analysis of the 16S rRNA gene that support a conceptual model in which common marine subsurface taxa persist into the subsurface, while high temperature adapted archaeal taxa show localized peaks in abundances in the hydrothermal clay horizons. Specifically, the bacterial phylum Chloroflexi accounts for a major proportion of the total microbial community within the upper 10 mbsf, whereas high temperature archaea (Terrestrial Hot Spring Crenarchaeotic Group and methanotrophic archaea) appear in varying local abundances in deeper, hydrothermal clay horizons with higher in situ temperatures (up to 55°C, 15 mbsf). In addition, geochemical evidence suggests that methanotrophy may be occurring in various horizons. There is also relict DNA (i.e., DNA preserved after cell death) that persists in horizons where the conditions suitable for microbial communities have ceased.