Document Type

Article

Publication Date

11-8-2013

Keywords

subseafloor biosphere, contamination, IODP Expedition, Chikyu, hydrothermal field

Abstract

During the Integrated Ocean Drilling Program (IODP) Expedition 331 at the Iheya North hydrothermal system in the Mid-Okinawa Trough by the D/V Chikyu, we conducted microbiological contamination tests of the drilling and coring operations. The contamination from the drilling mud fluids was assessed using both perfluorocarbon tracers (PFT) and fluorescent microsphere beads. PFT infiltration was detected from the periphery of almost all whole round cores (WRCs). By contrast, fluorescent microspheres were not detected in hydrothermally active core samples, possibly due to thermal decomposition of the microspheres under high-temperature conditions. Microbial contamination from drilling mud fluids to the core interior subsamples was further characterized by molecular-based evaluation. The microbial 16S rRNA gene phylotype compositions in the drilling mud fluids were mainly composed of sequences of Beta- and Gammaproteobacteria, and Bacteroidetes and not archaeal sequences. The phylotypes that displayed more than 97% similarity to the sequences obtained from the drilling mud fluids were defined as possible contaminants in this study and were detected as minor components of the bacterial phylotype compositions in 13 of 37 core samples. The degree of microbiological contamination was consistent with that determined by the PFT and/or microsphere assessments. This study suggests a constructive approach for evaluation and eliminating microbial contamination during riser-less drilling and coring operations by the D/V Chikyu

Publication Title

Frontiers in Microbiology

Volume

4

First Page

327

DOI

10.3389/fmicb.2013.00327

Required Publisher's Statement

Copyright © 2013 Yanagawa, Nunoura, McAllister, Hirai, Breuker, Brandt, House, Moyer, Birrien, Aoike, Sunamura, Urabe, Mottl and Takai.

Subjects - Topical (LCSH)

Underwater drilling--Research--East China Sea; Offshore oil well drilling--East China Sea; Microbial contamination--Research East China Sea; Marine sediments

Subjects - Names (LCNAF)

Ocean-Drilling Program

Genre/Form

articles

Type

Text

Rights

Copying of this document in whole or in part is allowable only for scholarly purposes. It is understood, however, that any copying or publication of this document for commercial purposes, or for financial gain, shall not be allowed without the author’s written permission.

Creative Commons License

Creative Commons Attribution 4.0 License
This work is licensed under a Creative Commons Attribution 4.0 License.

Language

English

Format

application/pdf

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