The JOIDES Resolution Assessment Report, representing the results of a multi-phase, year-long community review, is now available on the USSSP website. Thanks to everyone who participated in the community survey and the September ‘17 JR Assessment Workshop, both of which provided crucial input to this report!
Authors: Akira Ijiri, Fumio Inagaki, Yusuke Kubo, Rishi R. Adhikari, Shohei Hattori, Tatsuhiko Hoshino, Hiroyuki Imachi, Shinsuke Kawagucci, Yuki Morono, Yoko Ohtomo, Shuhei Ono, Sanae Sakai, Ken Takai, Tomohiro Toki, David T. Wang, Marcos Y. Yoshinaga, Gail L. Arnold, Juichiro Ashi, David H. Case, Tomas Feseker, Kai-Uwe Hinrichs, Yojiro Ikegawa, Minoru Ikehara, Jens Kallmeyer, Hidenori Kumagai, Mark A. Lever, Sumito Morita, Ko-ichi Nakamura, Yuki Nakamura, Manabu Nishizawa, Victoria J. Orphan, Hans Røy, Frauke Schmidt, Atsushi Tani, Wataru Tanikawa, Takeshi Terada, Hitoshi Tomaru, Takeshi Tsuji, Urumu Tsunogai, Yasuhiko T. Yamaguchi, Naohiro Yoshida
Microbial life inhabiting subseafloor sediments plays an important role in Earth’s carbon cycle. However, the impact of geodynamic processes on the distributions and carbon-cycling activities of subseafloor life remains poorly constrained. We explore a submarine mud volcano of the Nankai accretionary complex by drilling down to 200 m below the summit. Stable isotopic compositions of water and carbon compounds, including clumped methane isotopologues, suggest that ~90% of methane is microbially produced at 16° to 30°C and 300 to 900 m below seafloor, corresponding to the basin bottom, where fluids in the accretionary prism are supplied via megasplay faults. Radiotracer experiments showed that relatively small microbial populations in deep mud volcano sediments (102 to 103 cells cm−3) include highly active hydrogenotrophic methanogens and acetogens. Our findings indicate that subduction-associated fluid migration has stimulated microbial activity in the mud reservoir and that mud volcanoes may contribute more substantially to the methane budget than previously estimated.
Authors: Jesse McNichol, Hryhoriy Stryhanyuk, Sean P. Sylva, François Thomas, Niculina Musat, Jeffrey S. Seewald, and Stefan M. Sievert
Below the seafloor at deep-sea hot springs, mixing of geothermal fluids with seawater supports a potentially vast microbial ecosystem. Although the identity of subseafloor microorganisms is largely known, their effect on deep-ocean biogeochemical cycles cannot be predicted without quantitative measurements of their metabolic rates and growth efficiency. Here, we report on incubations of subseafloor fluids under in situ conditions that quantitatively constrain subseafloor primary productivity, biomass standing stock, and turnover time. Single-cell-based activity measurements and 16S rRNA-gene analysis showed that Campylobacteria dominated carbon fixation and that oxygen concentration and temperature drove niche partitioning of closely related phylotypes. Our data reveal a very active subseafloor biosphere that fixes carbon at a rate of up to 321 μg C⋅L−1⋅d−1, turns over rapidly within tens of hours, rivals the productivity of chemosynthetic symbioses above the seafloor, and significantly influences deep-ocean biogeochemical cycling.
Authors: Tiantian Yu, Weichao Wu, Wenyue Liang, Mark Alexander Lever, Kai-Uwe Hinrichs, and Fengping Wang
Members of the archaeal phylum Bathyarchaeota are among the most abundant microorganisms on Earth. Although versatile metabolic capabilities such as acetogenesis, methanogenesis, and fermentation have been suggested for bathyarchaeotal members, no direct confirmation of these metabolic functions has been achieved through growth of Bathyarchaeota in the laboratory. Here we demonstrate, on the basis of gene-copy numbers and probing of archaeal lipids, the growth of Bathyarchaeota subgroup Bathy-8 in enrichments of estuarine sediments with the biopolymer lignin. Other organic substrates (casein, oleic acid, cellulose, and phenol) did not significantly stimulate growth of Bathyarchaeota. Meanwhile, putative bathyarchaeotal tetraether lipids incorporated 13C from 13C-bicarbonate only when added in concert with lignin. Our results are consistent with organoautotrophic growth of a bathyarchaeotal group with lignin as an energy source and bicarbonate as a carbon source and shed light into the cycling of one of Earth’s most abundant biopolymers in anoxic marine sediment.
Axial Seamount is the most magmatically active submarine volcano in the northeast Pacific and has been the focus of inter-disciplinary studies for over two decades. The range of scientific interests includes volcanology, geophysical characterization and monitoring, hydrothermal vent formation and geochemistry, quantification of heat and chemical fluxes, hydrogeology, and the diversity and evolution of microbiological and animal communities. Axial Seamount erupted in January 1998, April 2011, and April 2015, and is likely to erupt again in the coming years. The site, therefore, presents a unique opportunity to study the interaction between volcanic, hydrothermal, and biological responses to magmatic and volcanic events. Primarily for these reasons, Axial Seamount was chosen as one of the key sites on the National Science Foundations’ (NSF) Ocean Observatories Initiative’s (OOI) cabled observatory network, the Cabled Array (CA). The Axial workshop was held to explore how ocean drilling and related studies can complement seafloor-based investigations by gaining access to the subseafloor to expand our understanding of microbiological, geophysical, hydrologic, and geochemical processes, now that the CA is fully operational with data streaming live to shore from a diverse suite of cabled instruments.
We are pleased to announce the release of the JOIDES Resolution Assessment Report, and the accompanying JOIDES Resolution Community Survey Data Report, in support of the National Science Foundation’s request to the National Science Board for the renewal of funding for the JR facility for the next five years. The community overwhelmingly supports the JR and its ability to address high priority objectives of the IODP Science Plan. The Community Survey Data Report documents the responses of 876 of our colleagues, both national and international, and provides significant insights into the IODP community. The Workshop Report reflects the outstanding effort of the 81 attendees of the September 2017 workshop, “Assessment of the JOIDES Resolution in Meeting the Challenges of the IODP Science Plan”. Their tasks included developing expedition results reports in preparation for the workshop, reviewing comments from the Community Survey, and synthesizing the two datasets. The report includes the results of plenary sessions from the workshop that focused on future scientific opportunities that can be addressed in the next five years, as well as discussion surrounding the relationship of the JR to the National Science Foundation’s Sea Change report from 2015, in addition to a list of recommendations and updates for the next five years of JR operations.
Authors: P. Fryer, C.G. Wheat, T. Williams, E. Albers, B. Bekins, B.P.R. Debret, J. Deng, Y. Dong, P. Eickenbusch, E.A. Frery, Y. Ichiyama, K. Johnson, R.M. Johnston, R.T. Kevorkian, W. Kurz, V. Magalhaes, S.S. Mantovanelli, W. Menapace, C.D. Menzies, K. Michibayashi, C.L. Moyer, K.K. Mullane, J.-W. Park, R.E. Price, J.G. Ryan, J.W. Shervais, O.J. Sissmann, S. Suzuki, K. Takai, B. Walter, and R. Zhang
Abstract: Geologic processes at convergent plate margins control geochemical cycling, seismicity, and deep biosphere activity in subduction zones and suprasubduction zone lithosphere. International Ocean Discovery Program Expedition 366 was designed to address the nature of these processes in the shallow to intermediate depth of the Mariana subduction channel. Although no technology is available to permit direct sampling of the subduction channel of an intraoceanic convergent margin at depths up to 19 km, the Mariana forearc region (between the trench and the active volcanic arc) provides a means to access materials from this zone.
Authors: Susan Q. Lang, Gretchen L. Früh-Green, Stefano M. Bernasconi, William J. Brazelton, Matthew O. Schrenk & Julia M. McGonigle
Abstract: Hydrogen produced during water-rock serpentinization reactions can drive the synthesis of organic compounds both biotically and abiotically. We investigated abiotic carbon production and microbial metabolic pathways at the high energy but low diversity serpentinite-hosted Lost City hydrothermal field. Compound-specific 14C data demonstrates that formate is mantle-derived and abiotic in some locations and has an additional, seawater-derived component in others. Lipids produced by the dominant member of the archaeal community, the Lost City Methanosarcinales, largely lack 14C, but metagenomic evidence suggests they cannot use formate for methanogenesis. Instead, sulfate-reducing bacteria may be the primary consumers of formate in Lost City chimneys. Paradoxically, the archaeal phylotype that numerically dominates the chimney microbial communities appears ill suited to live in pure hydrothermal fluids without the co-occurrence of organisms that can liberate CO2. Considering the lack of dissolved inorganic carbon in such systems, the ability to utilize formate may be a key trait for survival in pristine serpentinite-hosted environments.
Whether this is your first or 100th time, planning for a cruise takes a lot of time, good communication and attention to details. Thorough planning is essential to a cruise’s success. To assist cruise participants, the UNOLS Office is pleased to announce the Cruise Planning Page on the UNOLS website. This information covers what you need to know to plan a successful cruise, beginning with the proposal writing phase through post-cruise documentation. The webpage includes a Cruise Planning timeline plus important information
regarding: Vessel-specific cruise planning websites; Working in foreign ports and obtaining Marine Science Research Clearances; Available equipment and services; Conducting isotope work – Radioisotopes, Natural Isotopes and Stable Isotopes. Whether you are a seasoned PI preparing for your next cruise or someone who
is contemplating requesting ship time, this information will help your project get off to the right start. If you have any questions about cruise planning or suggestions for the webpage, please contact the UNOLS office.
Authors: Heuer, V.B., Inagaki, F., Morono, Y., Kubo, Y., Maeda, L., and the Expedition 370 Scientists
Abstract: International Ocean Discovery Program (IODP) Expedition 370 explored the limits of the biosphere in the deep subseafloor where temperature exceeds the known temperature maximum of microbial life (~120°C) at the sediment/basement interface ~1.2 km below the seafloor. Site C0023 is located in the protothrust zone in the Nankai Trough off Cape Muroto at a water depth of 4776 m, in the vicinity of Ocean Drilling Program (ODP) Sites 808 and 1174. In 2000, ODP Leg 190 revealed the presence of microbial cells at Site 1174 to a depth of ~600 meters below seafloor (mbsf), which corresponds to an estimated temperature of ~70°C, and reliably identified a single zone of elevated cell concentrations just above the décollement at around 800 mbsf, where temperature presumably reached 90°C; no cell count data was reported for other sediment layers in the 70°–120°C range because the detection limit of manual cell counting for low-biomass samples was not low enough. With the establishment of Site C0023, we aimed to detect and investigate the presence or absence of life and biological processes at the biotic–abiotic transition utilizing unprecedented analytical sensitivity and precision. Expedition 370 was the first expedition dedicated to subseafloor microbiology that achieved time-critical processing and analyses of deep biosphere samples, conducting simultaneous shipboard and shore-based investigations.
When Lamont-Doherty assumed management of the U.S. Science Support Program (USSSP) in early 2015, one of our main goals was to make the IODP expedition staffing process as transparent as possible. As we approach our fourth year of management, we would like to provide some statistics on U.S. shipboard participation in IODP over the past three years, as well as advice for those aspiring to sail.
Authors: Patricia Fryer, Geoffrey Wheat, Trevor Williams, and the Expedition 366 Scientists
Abstract: Geologic processes at convergent plate margins control geochemical cycling, seismicity, and deep biosphere activity in subduction zones and suprasubduction zone lithosphere. International Ocean Discovery Program (IODP) Expedition 366 was designed to address the nature of these processes in the shallow to intermediate depth of the Mariana subduction channel. Although no technology is available to permit direct sampling of the subduction channel of an intraoceanic convergent margin at depths up to 18 km, the Mariana forearc region (between the trench and the active volcanic arc) provides a means to access this zone.
Authors: Rosalia Trias, Bénédicte Ménez, Paul le Campion, Yvan Zivanovic, Léna Lecourt, Aurélien Lecoeuvre, Philippe Schmitt-Kopplin, Jenny Uhl, Sigurður R. Gislason, Helgi A. Alfreðsson, Kiflom G. Mesfin, Sandra Ó. Snæbjörnsdóttir, Edda S. Aradóttir, Ingvi Gunnarsson, Juerg M. Matter, Martin Stute, Eric H. Oelkers & Emmanuelle Gérard
Abstract: Basalts are recognized as one of the major habitats on Earth, harboring diverse and active microbial populations. Inconsistently, this living component is rarely considered in engineering operations carried out in these environments. This includes carbon capture and storage (CCS) technologies that seek to offset anthropogenic CO2 emissions into the atmosphere by burying this greenhouse gas in the subsurface. Here, we show that deep ecosystems respond quickly to field operations associated with CO2 injections based on a microbiological survey of a basaltic CCS site. Acidic CO2-charged groundwater results in a marked decrease (by ~ 2.5–4) in microbial richness despite observable blooms of lithoautotrophic iron-oxidizing Betaproteobacteria and degraders of aromatic compounds, which hence impact the aquifer redox state and the carbon fate. Host-basalt dissolution releases nutrients and energy sources, which sustain the growth of autotrophic and heterotrophic species whose activities may have consequences on mineral storage.
After recent difficulties working in foreign ports, the funding agencies felt it important for scientists and operators within the U.S. Academic Research Fleet (ARF) to work together to take a closer look at these complex operations. The UNOLS Logistics Working Group, comprised of scientists, operators and funding agency representatives, reviewed current policies and sticking points around working in foreign ports and obtaining marine research clearances (MRC). The summary of their findings and their recommendations can be found in the UNOLS White Paper on Proposing, Planning, and Executing Logistics involved in Oceanographic Field Operations in Foreign Waters and Ports along with its Appendix 1-Detailed Recommendations and Considerations for Working in Foreign Ports and Obtaining Marine Science Research Clearances. These are must-reads for anyone planning to work in a foreign port or apply for an MRC. This includes seasoned PIs, new PIs, future PIs, lab technicians, vessel technicians, schedulers and operators alike. The documents help to outline the issues, responsibilities and key topics to consider when planning these complicated cruises. Please pass this email along. It is important that this information is disseminated throughout the community!
Authors: Roger D. Flood , Roberto A. Violante , Thomas Gorgas , Ernesto Schwarz , Jens Grützner , Gabriele Uenzelmann-Neben , F. Javier Hernández-Molina , Jennifer Biddle, Guillaume St-Onge, and APVCM workshop participants
Abstract. The Argentine margin contains important sedimentological, paleontological and chemical records of regional and local tectonic evolution, sea level, climate evolution and ocean circulation since the opening of the South Atlantic in the Late Jurassic–Early Cretaceous as well as the present-day results of post-depositional chemical and biological alteration. Despite its important location, which underlies the exchange of southern- and northern-sourced water masses, the Argentine margin has not been investigated in detail using scientific drilling techniques, perhaps because the margin has the reputation of being erosional. However, a number of papers published since 2009 have reported new high-resolution and/or multichannel seismic surveys, often combined with multi-beam bathymetric data, which show the common occurrence of layered sediments and prominent sediment drifts on the Argentine and adjacent Uruguayan margins. There has also been significant progress in studying the climatic records in surficial and near-surface sediments recovered in sediment cores from the Argentine margin. Encouraged by these recent results, our 3.5-day IODP (International Ocean Discovery Program) workshop in Buenos Aires (8–11 September 2015) focused on opportunities for scientific drilling on the Atlantic margin of Argentina, which lies beneath a key portion of the global ocean conveyor belt of thermohaline circulation. Significant opportunities exist to study the tectonic evolution, paleoceanography and stratigraphy, sedimentology, and biosphere and geochemistry of this margin.
Authors: Tiantian Yu, Qianyong Liang, Mingyang Niu, Fengping Wang
The archaeal phylum Bathyarchaeota, which is composed of a large number of diverse lineages, is widespread and abundant in marine sediments. Environmental factors that control the distribution, abundance and evolution of this largely diversified archaeal phylum are currently unclear. In this study, a new pair of specific primers that target the major marine subgroups of bathyarchaeotal 16S rRNA genes was designed and evaluated to investigate the distribution and abundance of Bathyarchaeota in marine sediments. The abundance of Bathyarchaeota along two sediment cores from the deep-sea sediments of South China Sea (SCS, each from the Dongsha and Shenhu area) was determined. A strong correlation was found between the bathyarchaeotal abundance and the content of total organic carbon (TOC), suggesting an important role of Bathyarchaeota in organic matter remineralisation in the sediments of SCS. Furthermore, diversity analysis revealed that subgroups Bathy-2, Bathy-8 and Bathy-10 were dominant bathyarchaeotal members of the deep-sea sediments in the SCS. Bathy-8 was found predominantly within the reducing and deeper sediment layers, while Bathy-10 occurred preferentially in the oxidizing and shallower sediment layers. Our study lays a foundation for the further understanding of the ecological functions and niche differentiation of the important but not well-understood sedimentary archaeal group.
Authors: Martin Krüger and Axel Schippers
Integrated Ocean Drilling Program (IODP) Expedition 347 to the Baltic Sea in 2013 was in line with the IODP Science Plan main research theme “Deep biosphere responses to glacial–interglacial cycles,” addressing questions such as deep biosphere evolution, its biogeochemical processes, and how the postglacial diffusive penetration of conservative seawater ions may alter the chemical composition and microbial physiology in the subseafloor biosphere. Consequently, we tried to enrich indigenous microorganisms at in situ conditions using a broad range of electron acceptors (for fermenters; Fe, Mn, and sulfate reducers; and methanogens), simple and complex carbon substrates (in mixtures or as single compounds), and a wide range of culture conditions (temperature and salinity) to cover varying environmental conditions and metabolic requirements. The most successful were enrichment cultures with a mix of polymeric substrates, which proved to be successful for all samples investigated. Also, iron- and manganese-reducing organisms could be enriched from all sites, whereas nitrate as an electron acceptor did not work well. Methanogenic enrichments were only successful for a few of the samples investigated. In these cases, different monomeric as well as complex substrates were converted to methane, indicating a metabolically versatile indigenous microbial community in the sediments.
Authors: Katrina I. Twing, William J. Brazelton, Michael D. Y. Kubo, Alex J. Hyer, Dawn Cardace, Tori M. Hoehler, Tom M. McCollom and Matthew O. Schrenk
Serpentinization is a widespread geochemical process associated with aqueous alteration of ultramafic rocks that produces abundant reductants (H2 and CH4) for life to exploit, but also potentially challenging conditions, including high pH, limited availability of terminal electron acceptors, and low concentrations of inorganic carbon. As a consequence, past studies of serpentinites have reported low cellular abundances and limited microbial diversity. Establishment of the Coast Range Ophiolite Microbial Observatory (California, U.S.A.) allowed a comparison of microbial communities and physicochemical parameters directly within serpentinization-influenced subsurface aquifers. Samples collected from seven wells were subjected to a range of analyses, including solute and gas chemistry, microbial diversity by 16S rRNA gene sequencing, and metabolic potential by shotgun metagenomics, in an attempt to elucidate what factors drive microbial activities in serpentinite habitats. This study describes the first comprehensive interdisciplinary analysis of microbial communities in hyperalkaline groundwater directly accessed by boreholes into serpentinite rocks. Several environmental factors, including pH, methane, and carbon monoxide, were strongly associated with the predominant subsurface microbial communities. A single operational taxonomic unit (OTU) of Betaproteobacteria and a few OTUs of Clostridia were the almost exclusive inhabitants of fluids exhibiting the most serpentinized character. Metagenomes from these extreme samples contained abundant sequences encoding proteins associated with hydrogen metabolism, carbon monoxide oxidation, carbon fixation, and acetogenesis. Metabolic pathways encoded by Clostridia and Betaproteobacteria, in particular, are likely to play important roles in the ecosystems of serpentinizing groundwater. These data provide a basis for further biogeochemical studies of key processes in serpentinite subsurface environments.
Topic Editors: Anke Marianne Herrman, Doug LaRowe, Alain F. Plante. Energy is continuously transformed in the environment through the metabolic activities of organisms. These transformations of energy, i.e. bioenergetics, underpin most biogeochemical cycles on Earth and allow the delivery of a wide range of life-supporting ecosystem services. The aim of this Research Topic is to gather contributions from scientists working in diverse disciplines who have a common interest in evaluating bioenergetics at various spatial and temporal scales in a variety of different environments. The spatial scales range from the process and organismal level up to ecosystems, the temporal scales range from the near-instantaneous to the millennial, and the scientific disciplines involved include: soil scientists, biogeochemists, organic geochemists, microbial and ecosystem ecologists etc. Articles can be original research, techniques, reviews or synthesis papers. We encourage manuscripts focusing on interdisciplinary interactions addressing both basic and applied research as well as associated theoretical work. The overarching goal of this Research Topic is to demonstrate the environmental breadth of bioenergetics, and foster understanding between different scientific communities who may not always be aware of one another’s work. Abstract submission deadline: June 30, 2017.
Authors: Céline Pisapia, Emmanuelle Gérard, Martine Gérard, Léna Lecourt, Susan Q. Lang, Bernard Pelletier, Claude E. Payri, Christophe Monnin, Linda Guentas, Anne Postec, Marianne Quéméneur, Gaël Erauso and Bénédicte Ménez
Despite their potential importance as analogs of primitive microbial metabolisms, the knowledge of the structure and functioning of the deep ecosystems associated with serpentinizing environments is hampered by the lack of accessibility to relevant systems. These hyperalkaline environments are depleted in dissolved inorganic carbon (DIC), making the carbon sources and assimilation pathways in the associated ecosystems highly enigmatic. The Prony Bay Hydrothermal Field (PHF) is an active serpentinization site where, similar to Lost City (Mid-Atlantic Ridge), high-pH fluids rich in H2 and CH4 are discharged from carbonate chimneys at the seafloor, but in a shallower lagoonal environment. This study aimed to characterize the subsurface microbial ecology of this environment by focusing on the earliest stages of chimney construction, dominated by the discharge of hydrothermal fluids of subseafloor origin. By jointly examining the mineralogy and the microbial diversity of the conduits of juvenile edifices at the micrometric scale, we find a central role of uncultivated bacteria belonging to the Firmicutes in the ecology of the PHF. These bacteria, along with members of the phyla Acetothermia and Omnitrophica, are identified as the first chimneys inhabitants before archaeal Methanosarcinales. They are involved in the construction and early consolidation of the carbonate structures via organomineralization processes. Their predominance in the most juvenile and nascent hydrothermal chimneys, and their affiliation with environmental subsurface microorganisms, indicate that they are likely discharged with hydrothermal fluids from the subseafloor. They may thus be representative of endolithic serpentinization-based ecosystems, in an environment where DIC is limited. In contrast, heterotrophic and fermentative microorganisms may consume organic compounds from the abiotic by-products of serpentinization processes and/or from life in the deeper subsurface. We thus propose that the Firmicutes identified at PHF may have a versatile metabolism with the capability to use diverse organic compounds from biological or abiotic origin. From that perspective, this study sheds new light on the structure of deep microbial communities living at the energetic edge in serpentinites and may provide an alternative model of the earliest metabolisms.
Authors: Janelle J. Sikorski and Brandon R. Briggs
Microbial processes in the deep biosphere affect marine sediments, such as the formation of gas hydrate deposits. Gas hydrate deposits offer a large source of natural gas with the potential to augment energy reserves and affect climate and seafloor stability. Despite the significant interdependence between life and geology in the ocean, coverage of the deep biosphere is generally missing in most introductory oceanography textbooks, so there is a need for instructional materials on this important topic. In response to this need, a course module on the deep biosphere with a focus on gas hydrate deposits was created. The module uses Google Earth (Google, Mountain View, CA) to support inquiry-based activities that demonstrate the interaction of the deep biosphere with geology. The module was tried as both a series of in-class exercises and as an out-of-class assignment in an introductory, undergraduate oceanography course. The students took short, preactivity and postactivity quizzes to determine the effectiveness of the module in improving student knowledge about gas hydrates. The module was effective at increasing student knowledge about the basic environmental and biological controls on the formation of gas hydrates on the seafloor. Students showed a consistently low initial comprehension of the content related to gas hydrates, but most (>80%) of the students increased their quiz scores for all module activities. This module on gas hydrate deposits increases the available teaching resources focused on the deep biosphere for geoscience educators.
Authors: André Friese, Jens Kallmeyer, Jan Axel Kitte, Ivan Montaño Martínez, Satria Bijaksana, Dirk Wagner, the ICDP Lake Chalco Drilling Science Team and the ICDP Towuti Drilling Science Team
Subsurface exploration relies on drilling. Normally drilling requires a drilling fluid that will infiltrate into the drill core. Drilling fluid contains non-indigenous materials and microbes from the surface, so its presence renders a sample unsuitable for microbiological and many other analyses. Because infiltration cannot be avoided, it is of paramount importance to assess the degree of contamination to identify uncontaminated samples for geomicrobiological investigations. To do this, usually a tracer is mixed into the drilling fluid. In past drilling operations a variety of tracers have been used, each has specific strengths and weaknesses. For microspheres the main problem was the high price, which limited their use to spot checks or drilling operations that require only small amounts of drilling fluid. Here, we present a modified microsphere tracer approach that uses an aqueous fluorescent pigment dispersion with a similar concentration of fluorescent particles as previously used microsphere tracers. However, it costs four orders of magnitude less, allowing for a more liberal use even in large operations. Its applicability for deep drilling campaigns was successfully tested during two drilling campaigns of the International Continental Drilling Program (ICDP) at Lake Towuti, Sulawesi, Indonesia, and Lake Chalco, Mexico. Quantification of the tracer requires only a fluorescence microscope or a flow cytometer. The latter allowing for high-resolution data to be obtained directly on-site within minutes and with minimal effort, decreasing sample processing times substantially relative to traditional tracer methods. This approach offers an inexpensive, rapid, but powerful alternative technique for contamination assessment during drilling campaigns.
International Ocean Discovery Program (IODP) Expedition 357 successfully cored an east–west transect across the southern wall of Atlantis Massif on the western flank of the Mid-Atlantic Ridge (MAR) to study the links between serpentinization processes and microbial activity in the shallow subsurface of highly altered ultramafic and mafic sequences that have been uplifted to the seafloor along a major detachment fault zone. The primary goals of this expedition were to (1) examine the role of serpentinization in driving hydrothermal systems, sustaining microbial communities, and sequestering carbon; (2) characterize the tectonomagmatic processes that lead to lithospheric heterogeneities and detachment faulting; and (3) assess how abiotic and biotic processes change with variations in rock type and progressive exposure on the seafloor. To accomplish these objectives, we developed a coring and sampling strategy centered on the use of seabed drills—the first time that such systems have been used in the scientific ocean drilling programs. This technology was chosen in the hope of achieving high recovery of the carbonate cap sequences and intact contact and deformation relationships. The expedition plans also included several engineering developments to assess geochemical parameters during drilling; sample bottom water before, during, and after drilling; supply synthetic tracers during drilling for contamination assessment; acquire in situ electrical resistivity and magnetic susceptibility measurements for assessing fractures, fluid flow, and extent of serpentinization; and seal boreholes to provide opportunities for future experiments.
The Integrated Ocean Drilling Program (IODP) Expedition 337 was the first expedition dedicated to subseafloor microbiology that used riser-drilling technology with the drilling vessel Chikyu. The drilling Site
C0020 is located in a forearc basin formed by the subduction of the Pacific Plate off the Shimokita Peninsula,
Japan, at a water depth of 1180 m. Primary scientific objectives during Expedition 337 were to study the relationship between the deep microbial biosphere and a series of ∼ 2 km deep subseafloor coalbeds and to explore the limits of life in the deepest horizons ever probed by scientific ocean drilling. To address these scientific objectives, we penetrated a 2.466 km deep sedimentary sequence with a series of lignite layers buried around 2 km below the seafloor. The cored sediments, as well as cuttings and logging data, showed a record of dynamically changing depositional environments in the former forearc basin off the Shimokita Peninsula during the late Oligocene and Miocene, ranging from warm-temperate coastal backswamps to a cool water continental shelf. The occurrence of small microbial populations and their methanogenic activity were confirmed down to the bottom of the hole by microbiological and biogeochemical analyses. The factors controlling the size and viability of ultra-deep microbial communities in those warm sedimentary habitats could be the increase in demand of energy and water expended on the enzymatic repair of biomolecules as a function of the burial depth. Expedition 337 provided a test ground for the use of riser-drilling technology to address geobiological and biogeochemical objectives and was therefore a crucial step toward the next phase of deep scientific ocean drilling.