Tatsuhiro Fukuba

Japan Agency for Marine-Earth Science Technology, Kawasaki Si, Kanagawa, Japan

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Publications (43)32.11 Total impact

  • K. Hanatani · T. Fujii · T. Fukuba
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    ABSTRACT: Integrated and miniaturized in situ analyzers to estimate microbial biomass has been developed so far. The analyzer has the capability to perform the luciferin-luciferase bioluminescence reaction to determine the concentration of microbial adenosine-5′-triphosphate (ATP). The latest analyzer had been mounted on an ROV and evaluated at deep-sea environments. In this study, the method for in situ calibration that utilizes caged ATP as an internal standard is proposed to improve reliability of the in situ analyzer. Experiments confirmed that caged ATP was photolyzed with appropriate reproducibility by using a simple microfluidic device with the UV-LED light source.
    No preview · Article · May 2015
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    ABSTRACT: We present a novel underwater atomic force microscope system (underwater AFM system), which is mountable on underwater vehicles or submersible seafloor platforms. The mission of the system is to observe microorganisms and microparticulates in situ, which are suspended and dispersed in deepwater, with high spatial resolution down to nanometer scale. The system is composed of three major technological elements: a main unit of the underwater AFM, fluidic devices for the sample collection from deepwater (for example, pumps and a filtration unit using membrane filters), and robust mounting mechanisms for the underwater vehicles or the submersible seafloor platforms. Since we use a commercially available self-sensitive cantilever as the AFM probe, the deflection of the cantilever is measured by the integrated piezoresistive gauges. For insulation of the self-sensitive cantilever from the seawater under high pressure in the deep sea, we applied a thin layer coating of poly(p-xylylene) polymers (Parylene) onto the cantilever. We have successfully balanced the imaging quality and the insulation performance by optimizing the conditions of the layer formation, for example dimmer types of Parylene and the final layer thickness. We also have invented a novel sample stage for the underwater AFM equipped with a sample filtration mechanism using membrane filters. As a test result of the sample stage with the membrane filters in the deep sea exploration, the microorganisms suspended and dispersed in the deepwater have been successfully collected and fixed on the membrane filter. The present underwater AFM system would be a useful tool for in situ observation of the living microorganisms and microparticulates with nanoscale spatial resolution leading to future new findings in the deep sea.
    No preview · Article · May 2015
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    ABSTRACT: Spawning-condition Japanese eels Anguilla japonica, fertilized eggs, and newly-hatched preleptocephali have been captured, and studies for observing spawning eels with underwater camera systems have begun. This study describes a new, less invasive, free-drifting underwater camera observation system that was deployed from the research vessel (R/V) Natsushima in June 2013. Three drifting buoy camera systems (Una-Cam) with lights-on/lights-off programmed sequencing during daytime and nighttime hours were deployed over a period of seven days at 20 locations south of a salinity front along the southern West Mariana Ridge. Live artificially matured A. japonica eels held in transparent chambers were used as an attractant source through the release of reproductive pheromones and other odors. Each system was suspended from a buoy array at a depth of 174–200 m, with four cameras and three lights pointed downward at different angles towards the eel chamber. The Una-Cam systems were stable and were effective at recording images of fish, crustaceans, and gelatinous zooplankton. Olfactory cues may have attracted male and female Derichthys serpentinus eels, which showed what seemed to be reproductive behavior and attraction to the Japanese eels in the chamber. Una-Cam systems are capable of recording images of anguillid eels, if they approach, and may be useful for observing spawning eels in their offshore spawning areas.
    Full-text · Article · Jan 2015 · Fisheries Science
  • Tatsuhiro Fukuba · Takuroh Noguchi · Teruo Fujii
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    ABSTRACT: During NT10-16 cruise with R/V NATSUSHIMA and ROV HYPER-DOLPHIN in 2010, a new hydrothermal vent community was discovered at the Yoron Hole, where is the shallowest hydrothermal system in the known hydrothermal site found in the Okinawa Trough. The maximum temperature of clear smoker fluid was 247 °C, which was slightly lower than the boiling temperature (275 °C) of the seawater at the water pressure of 560-m water depth (5.6 MPa). Hydrothermal chimneys are composed of barite, sphalerite, galena, pyrite, chalcopyrite, and tetrahedrite. Although crustaceans and polychaetes were found around the hydrothermal vent, the diversity and population density were lower than that of the Iheya North Knoll and the Izena Hole hydrothermal sites.
    No preview · Article · Jan 2015
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    ABSTRACT: In 2010, we conducted seven surveys for the deep-sea hydrothermal plume through conductivity-temperature-depth profiler (CTD) “tow-yo” cast in the area of the Kairei field. We observed a turbidity anomaly with amaximumthickness of 120m, the upper limit of which was at 2,150m water depth, approximately 300 m above the Kairei field hydrothermal vents (~2,440 m). The depth of upper limit of turbidity anomaly around Kairei field was the same height as in previous reports. Because the maximum height of hydrothermal plumes are regulated by the density (temperature and salinity) of the end-member hydrothermal fluid and dilution by the ambient seawater, the height of the plume suggested that the hydrothermal activity of the Kairei field was also the same as 17 years ago. Deep sequencing of microbial 16S rRNA genes showed that the SUP05 phylotypes and Epsilonproteobacteria, which are known as the potential sulfur oxidizer and/or possibly hydrogen oxidizer, were propagated in the early stage of the hydrothermal plume and in the hydrothermal fluid–seawater mixing zone near the Kairei hydrothermal vents. Our exploration found a hydrothermal plume at 14 km north of the Kairei field, which had different H2/CH4 ratio expected fromthe end-member hydrothermal fluid of Kairei field and the ambient seawater mixing. The north plume had a lower H2, higher CH4 concentration, and higher microbial cell density than those in the hydrothermal plume around Kairei field. The north hydrothermal plume represented too oxic condition to harbor methane production by anaerobic methanogens. In addition, our microbial community structure analysis based on deep sequencing of 16S rRNA genes more than 10,000-amplicon reads per one sample showed no signal of methanogenic archaea. This suggests little in situ methanogenesis from H2 in the plume. It seems likely that high concentration of methane in the north plume is derived from another hydrothermal plume source rather than the Kairei hydrothermal fluids. Further studies will be needed to understand the cause of high methane concentration in the north plume.
    No preview · Article · Jan 2015
  • Kei Okamura · Taku Sugiyama · Takuroh Noguchi · Tatsuhiro Fukuba · Kyoko Okino
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    ABSTRACT: A deep-sea hydrogen sulfide ion (HS–) sensor was developed using electrochemical techniques for the direct measurement of hydrogen sulfide ion. In the sensor, linear sweep voltammetry is applied using three simple electrodes, Ag working electrode, Pt counter electrode and Ag/AgCl reference electrode. The measurement times are very small approximately 20 s. The sensor does not require an ion-selective membrane or chemical modification of the electrodes and are suitable for use in the deep-sea environment. In addition, the sensor is encased in a pressure-resistant container, and the electrodes have pressure adjustment functions. As a result, the sensor can withstand the temperature and pressure that exist up to 45°C and at water depths of 5000 m, respectively. With this sensor, it was possible to measure hydrogen sulfide ion levels with a detection limit of 2.2 μmol/L and a quantification range of 2.2–700 μmol/L. Field applications of the hydrothermal plume observations in the Mariana Trough and Okinawa Trough clarified the spatial distribution of hydrogen sulfide ion around the hydrothermal vents.
    No preview · Article · Jan 2015 · Geochemical journal GJ
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    Tatsuhiro Fukuba · Takuroh Noguchi · Teruo Fujii
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    ABSTRACT: The Irabu Knoll hydrothermal vents were first discovered in 2000 during YK00-06 cruise using R/V YOKOSUKA and manned submersible SHINKAI 6500. The Irabu Knoll consists of three seamounts from 1,680 to 1,970-m in water depth. The Irabu Knoll is located in the Southern Okinawa Trough and is constructed from basalt as the host rock. Two hydrothermal venting sites have been found at East and West seamount. Sulfide deposit of the Irabu Knoll hydrothermal system consists of barite, sphalerite, pyrite, and chalcopyrite. Major taxa in the vent ecosystem are Shinkaia crosnieri, Munidopsis sp., and Ashinkailepsas sp.
    Preview · Article · Jan 2015
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    ABSTRACT: Increasing anthropogenic CO2 in the atmosphere causes global warming and subsequent environmental changes, which may lead to an increase in natural disasters jeopardizing human society. Prompt technological development for CO2 capture and sequestration is required in the international community. In this study, we performed CO2 emission and shallow-type methane hydrate decomposition experiments at the Joetsu Knoll, offshore Joetsu, Niigata, Japan, as pilot studies to test feasibility of CO2 sequestration and methane recovery using methane-CO2 replacement in shallow-type methane hydrates. An isobaric cylinder pump and probe with a built-in heater (“Heat sonde”) were developed to inject CO2 in deep-sea, high-pressure conditions. Before injecting CO2 into a methane hydrate located in deep-sea sediments, we attempted CO2 emission directly into deep-seafloor. In the experiment, liquid CO2 was emitted at the head of Heat sonde, however, the isobaric cylinder pump became clogged during operation. The result reveals that precipitates of CO2 hydrate, which are generated during mixing of inflow seawater and outflow liquid CO2, blocked flow lines of the isobaric cylinder pump and Heat sonde. This suggests that our developed instruments must be improved for future work. We also observed the collapse of an exposed methane hydrate layer at the seafloor upon contact with the Heat sonde in our experiment.
    Full-text · Technical Report · Dec 2014
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    ABSTRACT: Pelagic cephalopods such as squid change coloration for camouflage or release ink as a defensive mechanism while being attacked by predators, which may block the view of the predator, have noxious chemical effects, or act as a warning signal for other squid (Bush and Robison 2007; Derby 2007; Wood et al. 2010). Pulsed releases of ink can also create “pseudomorphs” in the shape of squid that may serve as decoys to confuse predators about the location of the actual squid (Bush and Robison 2007; Wood et al. 2010). Some aspects of deep-sea squid behavior, including releases of their ink, have been observed using remote operated vehicles (ROV) (Hunt et al. 2000; Bush and Robison 2007), but most species have not been studied.During Hyper-Dolphin ROV (JAMSTEC) deployments over the West Mariana Ridge, observations were made of an unidentified species of pelagic squid (
    Full-text · Article · Jun 2014 · Marine Biodiversity
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    ABSTRACT: We developed a new multi-water-sampling system, ANEMONE-11, for autonomous underwater vehicle and remotely operated underwater vehicle exploration. Water samples are continuously collected by the ANEMONE-11 sampler by an in situ water pump at 40 mL/min and are sent to a selection valve unit that consists of 128 valves connected to 40 mL sampling bottles (50 cm in length). Each valve in the unit is selected and opened at preprogrammed intervals. We also discuss the results of observations at a hydrothermal area in the Okinawa Trough.
    Preview · Article · Jan 2014 · Methods in Oceanography
  • Christophe Provin · Tatsuhiro Fukuba · Kei Okamura · Teruo Fujii
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    ABSTRACT: Underwater hydrothermal vents draw a lot of interest as they are the shelter for unique ecosystems, besides being a possible new opportunity for ore mining. Manganese (Mn) is found at a high concentration in hydrothermal vents, which make it possible to use this metal ion as a tracer to detect and evaluate new hydrothermal sources. Here we present a miniaturized and integrated microfluidic system for the detection of Mn in deep-sea environment, called the integrated in situ analyzer for Mn2+ (IISA-Mn). The detection system is based on the chemiluminescence reaction of Mn contained in the seawater sample with a luminol-based reagent, which offers a high sensitivity. This system is composed of a microdevice for mixing and reaction, a pumping unit, several valving units, and a photomultiplier (PMT) detector. The system is able to detect Mn concentration above 280 nM in seawater, and gives a quite linear response until 500 nM. It is also proven to be able to work continuously during the 8 h of an actual remotely operated vehicle (ROV) dive. This system has led to the discovery of a previously unknown hydrothermal site in the Okinawa Trough.
    No preview · Article · Jan 2013 · IEEE Journal of Oceanic Engineering
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    ABSTRACT: Pressure and temperature characteristics of in-situ sensors have a big influence on measurements. A pH sensor using ISFET (Ion Sensitive Field Effect Transistor) is regarded as a suitable sensor for measurement pH at deep sea, however, its pressure and temperature characteristics were seldom studied. So, in this paper, we study the pressure and temperature characteristics of ISFET-pH sensor by the structural analysis and by the laboratory experiments, and then consider a new structure which can decrease the pressure effects on ISFET-pH sensor, and investigate these effects on the actual measurement in deep sea. From experimental and actual measurement results, we estimate the applications and efficiency of ISFET-pH sensor. By the results of structural analysis, if the structure of the sensor has sufficient strength for practical use, pressure effects occur. The experimental results shows the pressure and temperature characteristics have large individual difference. But by the results of structural improvement analysis, the pressure effects can be reduced by the change in construction material of the sensor. The actual measurement in deep sea indicates that the temperature characteristics depends on pressure, and show a problem of the present way of calibration that is to calibrate the effects of pressure and temperature, respectively.At the same time, it is also shown that the sensor has high sensitivity, good responsibility, wide application and good efficiency.
    No preview · Article · Jan 2012
  • T. Fukuba · C. Provin · K. Mogi · H. Kinoshita · K. Okamura · M. Kyo · T. Fujii
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    ABSTRACT: Microfluidic devices have been applied to realize functionally integrated and compact in situ chemical and biochemical analyzers that can be operated in deep-sea environments. PDMS-based microfluidic devices are connected with miniature pumps, valves, and flow-rate sensors to enable in situ detection of biomolecules or trace elements. The in situ analyzers can be mounted on a variety of underwater platforms such as remotely operated vehicles, autonomous underwater vehicles, and manned submersibles. Development, evaluation, and in situ operation processes of the in situ analyzers will be introduced together with practical operation results.
    No preview · Article · Jan 2012
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    ABSTRACT: This paper presents a simple method to change the hydrophilic nature of the glass surface in a poly(dimethylsiloxane) (PDMS)-glass hybrid microfluidic device to hydrophobic by an extra-heating step during the fabrication process. Glass substrates bonded to a native or oxygen plasma-treated PDMS chip having microchambers (12.5 mm diameter, 110 µm height) were heated at 200°C for 3 h, and then the hydrophobicity of the glass surfaces on the substrate was evaluated by measuring the contact angle of water. By the extra-heating process, the glass surfaces became hydrophobic, and its contact angle was around 109°, which is nearly the same as native PDMS surfaces. To demonstrate the usefulness of this surface modification method, a PDMS-glass hybrid microfluidic device equipped with microcapillary vent structures for pneumatic manipulation of droplets was fabricated. The feasibility of the microcapillary vent structures on the device with the hydrophobic glass surfaces are confirmed in practical use through leakage tests of the vent structures and liquid handling for the electrophoretic separation of DNA molecules.
    Full-text · Article · Jan 2012 · Analytical Sciences
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    ABSTRACT: In this paper, a rapid and simple method to determine the optimal temperature conditions for denaturant electrophoresis using a temperature-controlled on-chip capillary electrophoresis (CE) device is presented. Since on-chip CE operations including sample loading, injection and separation are carried out just by switching the electric field, we can repeat consecutive run-to-run CE operations on a single on-chip CE device by programming the voltage sequences. By utilizing the high-speed separation and the repeatability of the on-chip CE, a series of electrophoretic operations with different running temperatures can be implemented. Using separations of reaction products of single-stranded DNA (ssDNA) with a peptide nucleic acid (PNA) oligomer, the effectiveness of the presented method to determine the optimal temperature conditions required to discriminate a single-base substitution (SBS) between two different ssDNAs is demonstrated. It is shown that a single run for one temperature condition can be executed within 4 min, and the optimal temperature to discriminate the SBS could be successfully found using the present method.
    Full-text · Article · Dec 2011 · International Journal of Molecular Sciences
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    ABSTRACT: In this study, a totally integrated in situ analyzer for microbial gene detection has been developed for oceanography applications. A PDMS–glass microfluidic device that is capable of cell lysis, DNApurification, PCR, and optical detection has been utilized as the core element of the in situ analyzer. Microbial genomic DNA is purified and concentrated on glass beads packed in the microfluidic device. PCR is performed in a flow-through manner, and the amplified products are fluorescently detected using optical fibers. The sensitivity of a completed analyzer with deep-sea operation capabilities has been evaluated in a laboratory setting, and the analyzer has been operated in real deep-sea environments. Field evaluations have shown that the amplification of the eubacterial universal 16S rRNA gene and the recovery of the PCR product to the surface are successfully achieved in deep-sea environments.
    No preview · Article · Nov 2011 · RSC Advances
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    ABSTRACT: We have developed and tested a functionally integrated in situ analyzer, the IISA-ATP system, for microbial activity assays based on a quantitative determination of the total (particulate and dissolved) ATP in ocean environments. The IISA-ATP utilizes a PDMS-glass hybrid microfluidic device as its core functional element, which can perform cell lysis and total ATP quantification by a luciferin-luciferase bioluminescence assay in situ. Transparent heaters and a temperature sensor fabricated on a glass substrate provide temperature control. As a result of the evaluation using the microfluidic device with ATP standard solutions, the bioluminescence intensity was linearly correlated with 2 × 10(-12) to 2 × 10(-8) M of ATP. A detection limit of 1.1 × 10(-11) M was determined using the completed IISA-ATP system, which includes a miniature pumping module and a control module. As a result of the evaluation using the environmental seawater sample collected from Tokyo Bay, Japan, 2.7 × 10(-10) M of total ATP was successfully determined in the laboratory by the IISA-ATP. The system was operated at a shallow submarine hot spring area in Okinawa, Japan for an in situ trial. The result shows the system was successfully operated in situ and the total ATP was determined to be 3.4 × 10(-10) M.
    No preview · Article · Aug 2011 · Lab on a Chip
  • C. Provin · T. Fukuba · K. Okamura · T. Fujii
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    ABSTRACT: Hydrothermal anomalies found in the deep sea are a place where unique ecosystems exist, and may become a possible new resource for metallic ore mining. Elements such as iron and manganese are found in high concentration in hydrothermal vents. Therefore it is possible to use such metal ions as a tracer to detect and evaluate new hydrothermal sources. Here we present a miniaturized and integrated microfluidic system for the detection of manganese in deep-sea environment, called IISA-Mn (In Situ Integrated Analyzer for Mn 2+ ). The detection system is based on the chemiluminescence reaction of manganese contained in the seawater sample with a luminol-based reagent, which offers a high sensitivity. This system is composed of a microdevice for mixing and reaction, a pumping unit, several valving units, and a PMT (photomultiplier) detector. The system is able to detect manganese concentration above 100 nM in seawater, and gives a linear response until 1 µ M. It is also proven to be able to work continuously during the 8 hours of an actual dive. This system has lead to the discovery of a previously unknown hydrothermal site near Okinawa Islands.
    No preview · Article · Apr 2011
  • C. Provin · T. Fukuba · H. Kinoshita · K. Okamura · T. Fujii
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    ABSTRACT: This paper reports the development of a multilayer microfluidic device for continuous flow analysis of manganese in deep-sea environment, which was successfully evaluated during a scientific cruise and helped to discover new hydrothermal sources. The specific feature of the device is the on-chip integration of several flow control elements such as a Tesla mixer, flow regulator and valves to achieve a system with a very small footprint.
    No preview · Article · Jan 2011
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    ABSTRACT: Sequential operations of pre-separation reaction process by picoliter droplets and following electrophoretic separation process were realized in a single microfluidic device with pneumatic handling of liquid. The developed device consists of a fluidic chip made of PDMS, an electrode substrate, and a temperature control substrate on which thin film heater/sensor structures are fabricated. Liquid handling, including introduction of liquid samples, droplet generation, and merging of droplets, was implemented by pneumatic manipulation through microcapillary vent structures, allowing air to pass and stop liquid flow. Since the pneumatic manipulations are conducted in a fully automated manner by using a programmable air pressure control system, the user simply has to load liquid samples on each liquid port of the device. Droplets of 420 pL were generated with an accuracy of ± 2 pL by applying droplet generation pressure in the range of 40-100 kPa. As a demonstration, a binding reaction of a 15 mer ssDNA with a peptide nucleic acid oligomer used as an oligoprobe followed by denaturing electrophoresis to discriminate a single-base substitution was performed within 1.5 min. By exploiting the droplet-on-demand capability of the device, the influence of various factors, such as reaction time, mixing ratio and droplet configurations on the ssDNA-peptide nucleic acid binding reaction in the droplet-based process, was studied toward realization of a rapid detection method to discriminate rapid single-base substitution.
    No preview · Article · Nov 2010 · Electrophoresis

Publication Stats

218 Citations
32.11 Total Impact Points

Institutions

  • 2013-2015
    • Japan Agency for Marine-Earth Science Technology
      Kawasaki Si, Kanagawa, Japan
  • 2003-2012
    • The University of Tokyo
      • Institute of Industrial Science
      白山, Tōkyō, Japan
  • 1999-2002
    • Hiroshima University
      • Graduate School of Biosphere Sciences
      Hirosima, Hiroshima, Japan