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Surveys and monitoring are essential to study the biology and ecology of coral reefs in order to understand the reasons behind reef demise and recovery. However, mesophotic coral ecosystems (MCEs) remain largely unknown compared to their shallow counterparts because it is difficult to observe the seafloor below 30 m depths. Here, we propose a seafloor observation method using a low-cost autonomous underwater vehicle (AUV). This method was developed to allow many people to easily perform underwater observations of MCEs, and is also applicable to general seafloor surveys, such as underwater artificial structures, hydrothermal vent fields, etc. The method possesses three important attributes to achieve effective surveys. First, it can be applied in highly rugged terrains and enables the AUV to track omnidirectional surfaces at high speed (Max. ~1 m/s). Second, it can produce a reliable three-dimensional (3D) image of the seafloor based on a depth sensor. Third, it can be used to estimate the flow velocity field. The proposed method was tested by using the AUV HATTORI-2, which is a lightweight, one-man portable AUV equipped with commercial off-the-shelf sensors. Our study area is the Sekisei Lagoon in the South Ryukyus, which represents the largest coral reef complex in Japan. The method enabled us not only to obtain a wide and high-definition 3D image of mesophotic coral reefs that captures detailed characteristics of marine habitats but also to acquire environmental data, such as flow velocity field and seawater temperature, spatially and temporally aligned with the 3D image.

This paper proposes a new method for cruising-type autonomous underwater vehicles (AUVs) to track rough seafloors at low altitudes while also maintaining a high surge velocity. Low altitudes are required for visual observation of the seafloor. The operation of AUVs at low altitudes and high surge velocities permits rapid seafloor imaging over a wide area. This method works without high-grade sensors, such as inertial navigation systems (INS), Doppler velocity logs (DVL), or multi-beam sonars, and it can be implemented in lightweight AUVs. The seafloor position is estimated based on a reflection intensity map defined on a vertical plane, using measurements from scanning sonar and basic sensors of depth, attitude, and surge velocity. Then, based on the potential method, a reference pitch angle is generated that allows the AUV to follow the seafloor at a constant altitude. This method was implemented in the AUV HATTORI, and a series of sea experiments were carried out to evaluate its performance. HATTORI (Highly Agile Terrain Tracker for Ocean Research and Investigation) is a lightweight and low-cost testbed designed for rapid and efficient imaging of rugged seafloors, such as those containing coral reefs. The vehicle succeeded in following a rocky terrain at an altitude of approximately 2 m with a surge velocity of approximately 0.8 m/s. This paper also presents the results of sea trials conducted at Ishigaki Island in 2017, where the vehicle succeeded in surveying the irregular, coral-covered seafloor.

Autonomous underwater vehicles (AUVs) play important roles in seafloor observation because of their ability to acquire detailed information on the marine environment. However, the utilization of AUVs is limited by their high construction and operating costs. Here we propose a new, low-cost AUV-based method of seafloor observation. The proposed method possesses three important attributes to achieve effective surveys. First, it can be applied in highly rugged terrains and the AUV can track omnidirectional surfaces at high speed (~1 [m/s]). Second, it can produce a reasonable 3D image of the seafloor based on a depth sensor. Third, it can estimate the flow velocity field. The proposed method was tested by using the AUV HATTORI-2, which is a lightweight, one-man portable AUV equipped with commercial off-the-shelf (COTS) sensors.

In this study, direct continuous measurements of deep-sea turbulent flows near the seafloor were made in the Izena Cauldron hydrothermal fields, Okinawa Trough, Japan, to understand the dynamics of the bottom mixed layer. The objectives of this study were to reveal time series fluctuations of deep-sea turbulence intensity, that is, the turbulence energy dissipation rate, using an expendable vertical microstructure profiler (VMP-X), and to correlate them with in situ environmental data (flow, turbidity, conductivity, temperature, and depth data) obtained from a monitoring station installed on the seafloor near the VMP-X observation point. The turbulence energy dissipation rate ( $\boldsymbol{\varepsilon}$ ) value near the seafloor changed from 10−10 to 10−7 W kg−1, and $\boldsymbol{\varepsilon}$ maxima were observed from a flood tide between ebb tides (13:00–15:30 and 20:30–23:00) around a depth of 960 m, whereas the $\boldsymbol{\varepsilon}$ values decreased to 10−9 W kg−1 during ebb tide. In the former case, the water temperature increased only slightly, but in the latter case, water temperature increased by 0.1 °C. Furthermore, the turbulent flow was relatively strong from the seafloor to a height of around 50 m from the bottom. Turbulent flow observation points were located to the west of the hydrothermal vent area. The bottom topography of this area is closed. Deep-sea current data were successfully obtained for the layers between the seafloor and 60 m above the bottom, and periodic fluctuations with east–west and north–south components were synchronously observed with water-level variations. According to these environmental data and complex (closed) bottom topography data, the increasing water temperature fluctuation may occur as a result of hydrothermal venting (transport or intrusion of warm water). Therefore, $\boldsymbol{\varepsilon}$ may be affected by hydrothermal venting. However, to better understand the dynamics of vertical mixing processes, more observational data, such as continuous turbulent flow data, are necessary. In future studies, we will collect and analyze more spatiotemporal field data using VMP-X to understand the dynamics of the bottom mixed layer and improve the accuracy of numerical models.

In this study, time series measurements of turbulent flows near the sea floor were taken at hydrothermal fields in the Okinawa Trough. The purpose of this study was to understand the dynamics of the bottom mixed layer (BML), reveal fluctuations in the time series of deep sea turbulent flows (the turbulent energy dissipation rates) using VMP-X, and correlate them with in-situ flow, turbidity, and conductivity, temperature, and depth data obtained from a monitoring station on the sea floor. At the Kumejima west field, time series fluctuations in turbulent energy dissipation rate () between the sea surface and the seafloor were successfully measured. The near the sea bottom changed from 10–10 to 10–7 (W kg-1) and the maximum was observed from a flood tide between ebb tides, and decreased to 10–9 (W kg-1) during the ebb tide on June 24. Moreover, the turbulent flow was relatively strong from the seafloor to a height of around 80 m above it, and water temperature rose 0.1–0.2 degrees Celsius. The measurement points were located approximately 900 m to the northwest of the hydrothermal vent area. Deep-sea current data were successfully recovered for the layers at depths between the seafloor and 30 m above it, and a periodic fluctuation with an amplitude of approximately 10 cm/s for the east-west and north-south components, which was synchronized with variations in the water level, was also observed. According to these environmental and complex bottom topography data, this characteristic water temperature fluctuation may occur as a result of hydrothermal venting (transport or intrusion of warm water). Therefore, the intensity of turbulence may also be affected by hydrothermal venting. However, further continuous in-situ observational data are necessary to understand the dynamics of the BML. In a future study, we will collect and analyze more spatiotemporal turbulent flow data to understand the dynamics of the BML and improve the accuracy of the numerical model.

Environmental impact assessment on the site of ocean resource exploration and exploitation is required to be conducted under regulatory guidelines to protect and preserve ecosystems and biodiversity. Thus, observatories that can achieve long-term monitoring are needed for such a purpose. In connection with this, we have developed a long-term ecosystem monitoring lander, called “LEMON lander,” and an equipment for its pinpoint and safe installation, called “pilot frame.” LEMON lander is attached at the pilot frame on deck and goes down to the seafloor by using an onboard winch. After the pilot frame landed on the seafloor, LEMON lander is released from the pilot frame. The falling distance from the pilot frame is less than 30cm and the safety during falling and landing is assured; moreover, the pilot frame is more than 330kgf in water and this allows to deploy at a target position even under a bit strong current. We have succeeded to deploy two LEMON landers by using the pilot frame for an actual mission. This paper focuses on the installation method using the pilot frame and reports the installation operation for the actual mission, together with brief introduction of LEMON lander.

In deep-sea mining, leakage of lifting water might have an adverse effect on phytoplankton. Therefore, understanding the fluctuation of phytoplankton is important for environmental impact assessment in deep-sea mining. In this study, the maximum fluorescence intensity (F m ) and maximum quantum yield (F v /F m ) of phytoplankton in the Okinawa trough and Izu-Ogasawara waters were determined using fast repetition rate fluorometry (FRRF). The peak F m was noted at a depth of 80–100 m, and the maximum F v /F m was recorded at a depth of 100–130 m. This result suggests the existence of subsurface chlorophyll maximum and distribution of phytoplankton groups with high photosynthetic capacity in the lower layer. Therefore, understanding the dynamics of phytoplankton in not only the surface layer but also the subsurface layer of the open ocean is important. Our observation results could be used as important baseline data. Furthermore, during monitoring surveys, immediately observing the fluctuation in phytoplankton and detecting the influence of lodged lifting water at an early stage are necessary. FRRF can rapidly measure the photosynthetic parameters of phytoplankton in-situ; this could render it suitable for use in monitoring surveys. Thus, observations using FRR fluorometer might be useful for environmental impact assessment in deep-sea mining.

Long-term monitoring of the seafloor environment off Otsuchi Bay, northeastern Japan, was carried out to investigate environmental changes of the deep-sea floor after the 2011 off the Pacific coast of the Tohoku Earthquake. We deployed two deep-sea stations, one on an upper continental slope site (around 300 m water depth) and the other on a bathyal (998 m) site, to measure current intensity and direction, water temperature, salinity, dissolved oxygen, and turbidity, and to obtain seafloor images. The monitoring period on the upper slope was 9 months (March–September 2013), and 14 months (August 2012–October 2013) at the bathyal site. The oceanographic data from the upper slope site recorded the seasonal exchange of water masses and dense marine snowfall from April to May 2013. On 7 December 2012, a large aftershock of the 2011 earthquake caused increased turbidity at the bathyal site, and seafloor photographs and videos recorded the disturbance and recovery of benthic habitats. The data from these deployments show that long-term monitoring can provide important oceanographic, biological, and sedimentological data from deep-sea sites. Together with shipboard and deep-tow observations and data collected by remotely operated vehicles, long-term monitoring can be a valuable tool for understanding deep-sea environments and their variability.

[1] The Integrated Ocean Drilling Program (IODP) Expedition 331 investigated the Iheya North hydrothermal field in the Okinawa Trough. Several post-drilling underwater vehicle investigations were conducted over 2 years to identify post-drilling changes in fluid discharge pattern, mineral deposition, and fluid chemistry. Drilling-induced high-temperature hydrothermal fluid vents were identified at deep holes not only near the naturally occurring NBC hydrothermal fluid vent (Site C0016) but also at the seafloor ∼450 m distal to the NBC vent (Site C0014), where no hydrothermal fluid discharge was observed prior to drilling. A chimney structure at Hole C0016A grew rapidly at the NBC mound crest, where only small chimneys had been found before drilling. A drilling-induced diffuse hydrothermal flow region spread at Site C0014, and this area was newly colonized by the galatheid crab. From a fluid chemistry perspective, the post-drilling hydrothermal fluids were enriched in Cl relative to seawater, although this fluid chemistry was not observed during the 12 years prior to drilling. The Cl-enriched fluid reservoir underlying the subseafloor impermeable layers, observed by IODP Expedition 331, is likely source for the Cl-enriched fluids discharging from the post-drilling vents. The drilling-induced physical disturbance of subseafloor hydrogeological structures would release such fluids to the seafloor. In turn, the rapid chimney growth at the NBC mound crest may also be attributed to highly turbulent fluid flow with the enlarged artificial vent of Hole C0016A, which can contribute to the retention of the fluid-seawater mixture for a sufficiently long period to precipitate sulfide/sulfate minerals on the seafloor.

A novel marine thermophilic and heterotrophic Anaerolineae bacterium in the phylum Chloroflexi, strain SW7 T , was isolated from an in situ colonization system deployed in the main hydrothermal vent of the Taketomi submarine hot spring field located on the southern part of Yaeyama Archipelago, Japan. The microbial community associated with the hydrothermal vent was predominated by thermophilic heterotrophs such as Thermococcaceae and Anaerolineae, and the next dominant population was thermophilic sulfur oxidizers. Both aerobic and anaerobic hydrogenotrophs including methanogens were detected as minor populations. During the culture-dependent viable count analysis in this study, an Anaerolineae strain SW7 T was isolated from an enrichment culture at a high dilution rate. Strain SW7 T was an obligately anaerobic heterotroph that grew with fermentation and had non-motile thin rods 3.5–16.5 µm in length and 0.2 µm in width constituting multicellular filaments. Growth was observed between 37–65°C (optimum 60°C), pH 5.5–7.3 (optimum pH 6.0), and 0.5–3.5% (w/v) NaCl concentration (optimum 1.0%). Based on the physiological and phylogenetic features of a new isolate, we propose a new species representing a novel genus Thermomarinilinea: the type strain of Thermomarinilinea lacunofontalis sp. nov., is SW7 T (=JCM15506 T =KCTC5908 T ).

In this study, the current fluctuations were measured at the hydrothermal fields in the Okinawa Trough (Hatoma Knoll, Irabu Knoll, and Iheya North field) to characterize the fluid environment. The purpose of this study was to reveal the fluctuations of the deep-sea currents using an acoustic Doppler current profiler (ADCP), and to correlate them with the development of a bottom mixed layer as predicted by a numerical model. An ADCP (Teledyne RD Instruments Workhorse Sentinel, 300 kHz) was installed on the seabed at the Hatoma Knoll (depth about 1500 m), Irabu Knoll (depth about 2000 m), and Iheya North field (depth about 1000 m). For each observation point, the deep-sea current data were successfully recovered in the layer at depths between the seafloor and 40–60 m above the seafloor. Notably, the measurement results obtained at the Hatoma Knoll and Iheya North field showed a remarkably interesting fluctuation. During a time period of approximately 3 h, the range in the depths at which the currents were successfully recorded increased in a pulse form, up to around the upper layer at 120 m, allowing measurements in almost all of the layers. The time period of this pulse corresponded to the shift from an ebb tide to high tide. With the exception of these pulses, the currents could only be recorded from the seafloor to about a 40 m layer. This result indicated that a suitable environment for ADCP measurements was formed only within this range. To investigate the cause, a numerical model experiment was performed for the bottom turbulence and subsequent occurrence of vertical mixing of the suspended particulate matter in the Okinawa Trough using a large-eddy simulation (LES) model. The simulated results suggested that the semidiurnal tide periodically enhances the bottom turbulence at intervals of approximately 6 h, with the result that the bottom mixed layer thickness increases to a maximum of approximately 40–60 m. It was concluded that a suitable environment for ADCP measurements near the deep seafloor was formed mainly by the bottom mixed layer corresponding to the tide.

We were involved in development of a small lander for low-price and usability. The free fall type hadal zone research lander called “Edokko No.1” consists of 3 glass spheres and wireless connectable rubber bridge, and an observation equipment and levitation transponder device can be installed in the glass sphere. A continuous monitoring operation of periodic variations of surrounding ecosystem at deep-seabed is essential for acquiring baseline data and knowledge towards proposal of an appropriate methodology for underwater environmental impact assessment. In the demonstration test in 2013, the video of the hadal zone at the depth of 7800m has been acquired. By the bate trap survey, to observe the amphipods and a hadal fish (Pseudoliparis amblystomopsis). We will demonstrate the transition of deep-sea ecosystem. Time-lapse observation of the seabed is useful to an understanding of the seabed environment.

For the purpose of environmental impact assessment (EIA) at deep-sea hydrothermal environments towards development and utilization of seafloor massive sulfide (SMS) deposits, we have been developing a cost effective cabled underwater observatory. To realize a flexible and expandable system configuration, the observatory has a simple star-type network and power supply topology by employing an Ethernet interface. Pressure hulls and a framework of the observatory are composed of glass or plastic material to avoid corrosion of metals caused by hydrothermal fluid during long-term operation. The first observatory that has physicochemical sensors, water current profilers, and a video instrument will be deployed at the Oomuro Hole hydrothermal site, the northern Izu-Ogasawara arc for the purpose of system demonstration and practical data acquisition.

Viruses play important roles in marine surface ecosystems, but little is known about viral ecology and virus-mediated processes in deep-sea hydrothermal microbial communities. In this study, we examined virus-like particle (VLP) abundances in planktonic and attached microbial communities, which occur in physical and chemical gradients in both deep and shallow submarine hydrothermal environments (mixing waters between hydrothermal fluids and ambient seawater and dense microbial communities attached to chimney surface areas or macrofaunal bodies and colonies). We found that viruses were widely distributed in a variety of hydrothermal microbial habitats, with the exception of the interior parts of hydrothermal chimney structures. The VLP abundance and VLP-to-prokaryote ratio (VPR) in the planktonic habitats increased as the ratio of hydrothermal fluid to mixing water increased. On the other hand, the VLP abundance in attached microbial communities was significantly and positively correlated with the whole prokaryotic abundance; however, the VPRs were always much lower than those for the surrounding hydrothermal waters. This is the first report to show VLP abundance in the attached microbial communities of submarine hydrothermal environments, which presented VPR values significantly lower than those in planktonic microbial communities reported before. These results suggested that viral lifestyles (e.g., lysogenic prevalence) and virus interactions with prokaryotes are significantly different among the planktonic and attached microbial communities that are developing in the submarine hydrothermal environments., 論文

At Sekisei Reef in southwestern Japan (24° N), coral cover dramatically decreased in the mid-1980s, probably due to a population outbreak of the coral predator Acanthaster planci. Coral communities subsequently recovered well outside the semiclosed lagoon, but recovery has been poor inside it. Hence, water-quality degradation including eutrophication has been a concern inside the lagoon. In addition, temporal variation in eutrophication parameters is common among high-latitude coral reefs, resulting in difficulties in evaluating them. Therefore, to address these issues, we monitored temperature, salinity, turbidity, chlorophyll-a, NO x -N (NO3-N + NO2-N), and NH4-N concentrations year-round across the lagoon at Sekisei Reef. Turbidity and NO x -N concentration increased with increasing wind velocity, suggesting that variation in turbidity and NO x -N concentrations was attributed to resuspension of bottom sediments, and NO x -N release through regeneration processes of micro-organisms from the s...

The periodicity of the bubble jet that spouts intermittently from the Taketomi submarine hot spring in Yaeyama archipelago, Japan, was measured for the first time using an acoustic current meter. The time series analysis of the upward velocity for the data, without a spiky signal, indicates that the cycle fluctuates between 38 and 85 s. Focusing on the period of high and low tide, the dominant time cycles were 66 and 41 s, respectively. These results show that the fluctuation of pressure with tide affected the eruption period of the bubble jet. In accordance with the vertical tube theory, estimations of thermal source and recharge water temperatures were carried out by taking into account the boiling point change due to the tidal variation in hydrostatic pressure. The result indicated that if the heat source temperature was higher than 200.0 °C and recharge water temperature was preheated to 117.96 °C, the observed eruption time cycles at high and low tide were stable.

A ceramic coral settlement device (CSD) was developed to raise juvenile corals in situ in preparation for transplantation. The CSD is designed to be deployed in the water before mass spawning of corals, allowing larvae to settle and grow on the CSD before it is fixed to the reef structure. CSDs were aggregated and fixed on 0.2-m2 frames (either 648 or 720 CSDs per frame) and deployed in the Sekisei Lagoon around the full moons of April and May in 2002. Seven frames were collected in August 2002 and settled corals were counted in the laboratory. The maximum number of coral colonies settled on CSDs in one frame was 617, with 94% belonging to the genus Acropora. The aggregated CSDs successfully functioned as a coral settlement substratum, with more appropriate arrangement of CSDs on the frame, enabling greater exposure to sunlight and currents, which is expected to increase the amount of settlement.

Microbial communities in a shallow submarine hydrothermal system near Taketomi Island, Japan, were investigated using cultivation-based and molecular techniques. The main hydrothermal activity occurred in a craterlike basin (depth, ∼23 m) on the coral reef seafloor. The vent fluid (maximum temperature, >52°C) contained 175 μM H 2 S and gas bubbles mainly composed of CH 4 (69%) and N 2 (29%). A liquid serial dilution cultivation technique targeting a variety of metabolism types quantified each population in the vent fluid and in a white microbial mat located near the vent. The most abundant microorganisms cultivated from both the fluid and the mat were autotrophic sulfur oxidizers, including mesophilic Thiomicrospira spp. and thermophilic Sulfurivirga caldicuralii . Methane oxidizers were the second most abundant organisms in the fluid; one novel type I methanotroph exhibited optimum growth at 37°C, and another novel type I methanotroph exhibited optimum growth at 45°C. The number of hydrogen oxidizers cultivated only from the mat was less than the number of sulfur and methane oxidizers, although a novel mesophilic hydrogen-oxidizing member of the Epsilonproteobacteria was isolated. Various mesophilic to hyperthermophilic heterotrophs, including sulfate-reducing Desulfovibrio spp., iron-reducing Deferribacter sp., and sulfur-reducing Thermococcus spp., were also cultivated. Culture-independent 16S rRNA gene clone analysis of the vent fluid and mat revealed highly diverse archaeal communities. In the bacterial community, S. caldicuralii was identified as the predominant phylotype in the fluid (clonal frequency, 25%). Both bacterial clone libraries indicated that there were bacterial communities involved in sulfur, hydrogen, and methane oxidation and sulfate reduction. Our results indicate that there are unique microbial communities that are sustained by active chemosynthetic primary production rather than by photosynthetic production in a shallow hydrothermal system where sunlight is abundant.

Our knowledge of the reproductive biology and ecology of most deep-sea animals is very limited due to the logistic difficulties of deep-sea investigations. In this study, spawning by males and females of the vesicomyid bivalve Calyptogena soyoae and C. okutanii complex were observed in situ over 1 yr using the long-term deep-sea observatory located at cold seeps in Sagami Bay, Japan. Eggand sperm-spawning events by clam aggregations occurred roughly 90 and 213 times m–2 for 1 yr, respectively, and the local population of the C. soyoae and C. okutanii complex yielded 5.8 × 108 eggs m–2 yr–1 into the water column over the seep location studied. Males displayed a ‘sprinkle siphon’ behavior, waving their siphons left and right to sprinkle sperm into the water. Female spawning by egg release into the water column was always preceded by male spawning and decreasing near-bottom current speeds. Two hypotheses are proposed for cues to stimulate egg release by C. soyoae/okutanii females. First, a ‘double trigger’ hypothesis requires the presence of sperm in the water column and decreasing current speed before eggs are released. Second, a ‘single trigger’ hypothesis requires that egg release is induced when compounds in or released with sperm exceed a threshold concentration. These results demonstrate the utility of long-term observatories for studies of deep-sea reproductive biology, particularly for species characterized by rare, episodic spawning events.

We report the first study of sperm whale-fall ecosystems, based on mass sinking of whale carcasses at shelf depths in the northwest Pacific. We conducted three observations over a 2-year period on replicate sperm-whale carcasses implanted at depths of 219‐254 m off the southern part of Japan from July 2003 to August 2005. The study was made possible by a mass stranding of sperm whales in January 2002, and the subsequent sinking of 12 carcasses in the waters off Cape Nomamisaki. Dense aggregations of unique chemosynthesis-based fauna had formed around the whale carcasses after 18 months (July 2003). The mytilid mussel Adipicola pacifica was the most abundant macrofaunal species and covered most of the exposed bone surfaces. The general composition of the fauna was similar to that of deep-water reducing habitats, but none of the species appearing in this study has been found at hydrothermal vents, cold seeps or deep-water whale falls. A new species of lancelet, which was the first record of the subphylum Cephalochordata from reducing environments, a new species of Osedax; a rarely encountered benthic ctenophore, and a rare gastropod species were discovered at this sperm whale-fall site. Benthic communities were similar across all the carcasses studied, although the body sizes of the whales were very different. The succession of epifaunal communities was relatively rapid and the sulphophilic stage was considerably shorter than that of other known whale falls.

A synthetic aperture sonar gathers echoes from large area of seafloor per a ping, therefore the sonar needs wider width of the beam than Side scan sonar. But if the elements of the projector is just one element, it have to be small to widen the beam, and must be low sensitivity. One solutions to raise the sensitivity of the sonar is to use array as a receiver. The array is not only necessary for high sensitivity, but also the motion compensation and higher mapping rate in synthetic aperture process. Many synthetic aperture sonar are now constructed with a single transmitter with an arrayed receiver. But the projector remains small and single in many synthetic aperture sonars. The maximum detection range of synthetic aperture sonar was no longer than side scan sonar at same sonic frequency yet. To extend the sonar range, we proposed multi-channel projector whose elements lined vertically. We consider that the intensity of the projection beam increases keeping its width, by controlling a timing of the projection from each element. In addition, if the projector can receive echoes, 3D-maps can be generated simultaneously like a multi-beam echo sounder. This means synthesizing aperture process become more precise with the correct altitudes. In June 2014, we carried out survey with the synthetic aperture sonar totally for 40 hours over 5 days at off-Sanriku near border of Miyagi and Iwate prefecture. We evaluated the projector performance through detections of many artificial objects such as underwater reefs and sunken ship in the survey. We confirmed that projection beam was widen keeping projection power and maximum detection range was over 400 m in slant range. In addition, bottom detection process which is before step of 3D-mapping became easy.

We developed a pressure tight ultra violet (UV) light-emitting diode (LED) light for deep-sea floor optical imaging. It was confirmed by deep-sea in situ observation that many deep-sea organisms show fluorescent properties, and the fluorescent colors are unique for each deep-sea species. Additionally, we developed a pressure tight violet-laser-induced spectrometer for deep-sea remote inspection. It was confirmed by laboratory experiments that laser-induced fluorescence from oil in water shows characteristic fluorescent spectrum for each oil type. Fluorescent observation systems are expected to be useful tools for deep-sea floor inspection by mounting them on a remotely operated vehicle (ROV) or autonomous underwater vehicle (AUV).

A new technology is necessary for effective monitoring of deep-sea hydrothermal ecosystems towards the environmental impact assessment of marine mining projects. For this purpose, we develop a new deep-sea observation technique using bio-fluorescent characteristics. Ultraviolet (UV)-LED illumination and violet laser illumination are used for fluorescent video recording of a variety of deep-sea organisms. This study reports the bio-fluorescent patterns and colours observed for a variety of deep-sea organisms and their usefulness for monitoring.

Novel thermophilic bacteria, designated strains VW1 and MM1T, were isolated from hydrothermal fluid and microbial mat samples, respectively, collected from a shallow marine hydrothermal system (water depth 22 m) occurring in coral reefs off Taketomi Island, Okinawa, Japan. Cells of the two novel strains were motile rods with a single polar flagellum in the exponential growth phase. In a medium that included elemental sulfur, cells of the two strains became non-motile with oval to spherical cell shapes. For both strains, growth occurred at between 30 and 60 °C (optimum temperature of 50–55 °C; 60–80 min doubling time) and between pH 5.5 and 7.1 (optimum pH 6.0). The isolates were microaerobic chemolithoautotrophs capable of using thiosulfate or tetrathionate as the sole energy source, O2 as the sole electron acceptor and CO2 as the sole carbon source. Organic substrates, such as yeast extract and tryptone, inhibited growth of both strains. The G+C contents of genomic DNA were 51.3 and 49.5 mol% for strains VW1 and MM1T, respectively. Phylogenetic analysis based on 16S rRNA gene sequences indicated that the two strains were closely related to each other (99.9 % sequence similarity) and were distantly related to other previously described genera within the Gammaproteobacteria. The novel isolates could also be differentiated from other gammaproteobacterial genera on the basis of their physiological properties. It is suggested that the novel isolates represent the type species of a new genus, for which the name Sulfurivirga caldicuralii gen. nov., sp. nov. (type strain MM1T=JCM 13439T=DSM 17737T) is proposed.

Coral larvae, produced from a mass spawning event, were successfully settled on special stone settlement sticks and raised in situ for eventual transport to other reefs. The test area, Sekisei lagoon, Okinawa Prefecture, Japan, is located close to the warm Kuroshio current and is surmised to be the source from which major Japanese corals are derived. A total of 131 settlement sticks, with small holes in their sides to increase protection from grazing (4 mm in diameter and approximately 5 mm deep), were deployed in the lagoon the day before the coral’s mass spawning. After 3 months, 61 sticks were recovered containing 71 corals, mostly in the holes. After 1 year, three corals were confirmed to be growing well and extending outside the holes of the three sticks out of 70 sticks left in the water at the lagoon site. They survived two potentially lethal conditions, that is, high water temperatures with associated extensive coral bleaching and continuous grazing pressure from predators. This procedure is applicable for large-scale coral transplantation, not only in Japan but also in other tropical countries.

Time series physical properties of water column were measured at the Hatoma Knoll hydrothermal field on the Okinawa Trough, using a multi-layered Acoustic Doppler Current Profiler (ADCP). We aimed (1) to provide a deep-sea current data within a small and complicated geographical feature of a caldera and (2) to show the possibility of hydrothermal plume observation by ADCP during the measurement in April 2004 and May 2005 cruises. The deep-sea current data were recovered at the depths between seafloor and 40-m or 60-m-layers above the seafloor. Moreover, acoustic reflection signals were sometimes observed up to 120-m layer above the seafloor due to the trail of hydrothermal plumes. A power spectrum density analysis by fast Fourier transform (FFT) showed the dominant time cycle of the horizontal current velocity, which corresponded to tidal periodicity over an approximate 12-hours period, at each layer. Residual currents, which play an important role in material transport, tended to northwest direction and suggested that most of material might keep retaining within the caldera. The causes of the measurement result of the flow which appeared into a pulse form may indicate fluctuation of the blowout of hydrothermal water. The verification of the fluid mechanism by the numerical model in the local field such as the caldera will be necessary in the future.

The doubling time of indigenous bacteria in mixing-zone of hydrothermal fluid and seawater was determined using a diffusion chamber unit deployed on the field of Hatoma Knoll (24° 51.50′N, 123° 50.50′ E), which is a submarine volcano located on southern Okinawa Trough. The diffusion chamber is a reliable tool to incubate and to directly measure the microbial growth under in situ condition of deep-sea, although an operation of submersible and a complicated preparation of seed water became the technical constraints. The doubling time at non-vent site distant from active vent site was estimated from 86 to 110 h, while at active vent sites more rapid doubling time, 21–32 h, were estimated. A potential sulfur-oxidizing bacteria belonging to Epsilonproteobacteria dominated the population grew in the chambers, which were incubated using the plume water obtained from the mixing zone between the vent fluid and seawater, and Bathymodiolus colony, while no detection of Gammaproteobacteria. The methane-oxidizing bacteria were detected only from gill and digestive tract of Bathymodiolus platifrons, and could not be detected from the chamber, although the chamber was placed on Bathymodiolus colony. The results of this study suggested that chemolithoautotrophic growth near by the hydrothermal vent is sustained by the rapid doubling time of Epsilonproteobacteria using chemical species dissolved in fluid and provides the chemoautotrophic product to deep-sea benthopelagic community, as well as a microbial products in hydrothermal vent plume.

A novel methane-oxidizing bacterium, strain IT-9T, was isolated from a shallow submarine hydrothermal system occurring in a coral reef in Japan. Strain IT-9T was a Gram-negative, aerobic, motile, coccoid or oval-shaped bacterium with the distinctive intracytoplasmic membrane arrangement of a type I methanotroph. Strain IT-9T was a moderately thermophilic, obligate methanotroph that grew on methane and methanol at 30–55 °C (optimum 45–50 °C). The strain possessed the particulate methane monooxygenase (pMMO). The ribulose monophosphate pathway was operative for carbon assimilation. NaCl was required for growth within a concentration range of 1–5 % (optimum 3 %). The hao gene encoding hydroxylamine oxidoreductase (HAO) involved in nitrification was detected by a PCR experiment. The major phospholipid fatty acids were C16 : 0 and C18 : 1ω7c. The major isoprenoid quinone was Q-8. The DNA G+C content was 66.0 mol%. The 16S rRNA gene sequence of strain IT-9T was only moderately related to the sequences of members of the closest genera Methylohalobius (94.1 % similarity) and Methylothermus (91.7–91.9 % similarity); however, those sequences formed a deeply branching monophyletic group within the order Methylococcales . Phylogenies based on 16S rRNA gene sequences, deduced partial PmoA sequences and deduced partial Hao sequences and physiological and chemotaxonomic characteristics revealed that strain IT-9T represents a novel species of a new genus, for which the name Methylomarinovum caldicuralii gen. nov., sp. nov. is proposed. The type strain of Methylomarinovum caldicuralii is IT-9T ( = JCM 13666T = DSM 19749T). In addition, we propose a new family, Methylothermaceae fam. nov., in the order Methylococcales , to accommodate the genera Methylothermus , Methylohalobius and Methylomarinovum. The genera Methylothermus and Methylohalobius have been recognized as being distinct from other genera in the methane-oxidizing order Methylococcales in the class Gammaproteobacteria . These genera form a distinctive monophyletic lineage within the order on the basis of 16S rRNA gene sequence phylogeny. This seems consistent with their distinctive physiological traits; the genus Methylothermus includes the most thermophilic species, and the genus Methylohalobius includes the most halophilic species, within the order. Although these two genera include only three species at the time of writing, similar sequences of 16S rRNA genes and pmoA genes encoding pMMO have been detected in a geothermal area or deep-sea hydrothermal vent fields by studies using culture-independent techniques. This suggests that unknown methanotrophs of this lineage inhabit various extreme environments.

Two aerobic methane-oxidizing bacterial strains were isolated from distinct marine environments in Japan. Strains IT-4T and T2-1 were Gram-stain-negative, aerobic, motile, plump short rods or oval-shaped bacteria with a single polar flagellum and type I intracytoplasmic membranes. They were obligate methanotrophs that grew only on methane or methanol. Each strain possessed the particulate methane monooxygenase (pMMO). The ribulose monophosphate pathway was operative for carbon assimilation. The strains grew best at 37 °C, and did not grow at 45 °C. NaCl was required for growth within a concentration range of 1–8 % (w/v). The major phospholipid fatty acids were C16 : 0, C16 : 1ω7c, and C16 : 1ω5t. The major isoprenoid quinone was MQ-8. The DNA G+C content was 50.9–51.7 mol%. The 16S rRNA gene sequences of the strains showed 99.4 % similarity to each other, and DNA–DNA hybridization analysis indicated that the strains were representatives of the same species. The 16S rRNA gene sequences were highly similar to some marine environmental sequences (94.0–97.7 % similarity), but did not show similarities more than 94 % with sequences of members of other related genera, such as Methylomicrobium , Methylobacter , Methylomonas and Methylosarcina . Phylogenies based on 16S rRNA gene sequences and deduced partial PmoA sequences, and the physiological and chemotaxonomic characteristics revealed that strains IT-4T and T2-1 represent a novel species of a new genus in the family Methylococcaceae , for which the name Methylomarinum vadi gen. nov., sp. nov. is proposed. The type strain is IT-4T ( = JCM 13665T = DSM 18976T).

This paper describes the development of an apparatus which can take a time series of coral fluorescence images. The purpose of this study is to provide an outline of a “coral fluorescent protein monitoring system”. We discuss the method of acquisition of the fluorescent images and the prospects for future studies. Fluorescent proteins are very common in reef corals. For example, fluorescent proteins such as Midoriishi-Cyan (MiCy), which produces blue-green fluorescence, and Azami-Green (AG), which produces green fluorescence, were identified in Galaxea fascicularis and Acropora sp‥ A correlation between bleaching resistance in corals and the concentration of fluorescent proteins in their tissue was found after the large-scale bleaching event which struck the Great Barrier Reef in 1998. Therefore, coral fluorescence proteins play an important role in protecting coral zooxanthellae (symbiotic algae) against excessive sunlight. Coral bleaching occurs when zooxanthellae leave their coral host. The result of this loss is the whitening of coral colonies. Therefore fluctuations in the concentration of fluorescent proteins in corals may be used as an index of coral activity. The responses of coral activity to environmental changes in coral reef regions may be evaluated by carrying out simultaneous measurements of coral fluorescence and environmental parameters.

The periodicity of an under water geyser in the Taketomi submarine hot spring in Yaeyama archipelago, Japan, has been investigated. We concluded the time cycle of the geyser responds to the tide, after conducting the time series analysis of the upward velocity taken by an acoustic Doppler current meter. The time cycles in high and low tide were 66 s and 41 s, respectively. In accordance with the Bunsen's vertical tube theory, and assuming underground depth of heated domain was just 10 m below the sea bottom, that was backed up by the averaged integration of upward flux per each eruption, we also denoted the condition that temperature of heat source (Θ) of over 200 oC and the recharge water temperature (θ 0 ) of 130.57 oC could sustain the observed time cycles in high and low tide. These estimations of Θ were consistent with the previous estimations of the “deep underground water temperature” at the Taketomi Submarine Hot Spring, which ranged from 160 to 200 °C as reported by geochemists. Additionally, time variability of the relative bubble density and the relative bubble flux from the undersea geyser was investigated, utilizing the ultrasonic echo intensity and the upward velocity. A relational expression between the relative bubble density and the ultrasonic echo intensity were derived, after assuming that the (a)bubbles could be replaced by simple rigid spheres with a constant radius, (b)the bubble's radius was enough larger than the wavelength of the incident ultrasonic wave, and (c)the sound absorption by the seawater was constant. We demonstrated that at high tide, at erupting state the relative bubble density had large value, while at halting state it had quite small value. At low tide, however, the relative bubble density had almost always positive value, thus the bubbles were always present in the seawater. And the similarity between the relative bubble density and the upward velocity confirmed that the bubbles in the sea water were transported by the fluid discharged from the underwater geyser.

In order to improve the method for prediction of tuna fishing ground, the modification of the analysis about satellite altimeter data was made as trial. In this study, we focused on the satellite altimeter, TOPEX/POSEIDON series, to improve the method of fishing ground prediction. Fishery data were supplied as hook rate by local fishing information around Indonesia and hearing infromation. The gradient of sea surface height is calculated between the neighbor grid which has the maximum gradient. Result showed that the fishery data with hook rate over 0.8 are grouped in a zone from 1.0E-06 of sea prediction of fishing ground quantitatively, but also reasonable accuracy as shown in the change in the standard deviation. This method can be utilized for the effective fishing plan with the resource protection and the economy in the fishing operation in near future. Keywords: sea surface altimeter, sea surface gradient, remote sensing, fishing ground search, hook rate, fishery resource management.

Change in the sea surface height anomaly derived from satellite altimeter was examined and applied to evaluate the possibility of tsunami prediction before the occurance. Sea surface height anomaly was composed period during earthquake and tsunami occurance. Daily variability in the sea surface height anomaly was traced about the location of hypocenter, aftershock, and the end of erthquakes from satellite altimetry. Results shows that there are the locations where the sea surface height anomaly suddenly increased or decreased before tsunami event at least. This result can be utilized and applied for the development in not only the stunami monitoting system as the disaster monitoring, but also for the effective tsunami prediction system in the near future. Keywords: tsunami, earthquake, bottom topography, sea surface height, satellite altimetry, altimeter, disaster prevention.

A novel thermophilic and sulfur-reducing bacterium, strain S304(T), was isolated from the Taketomi submarine hot spring shallow hydrothermal field located at southern part of the Yaeyama Archipelago, Japan. The cells were non-motile short thick rods or oval cocci 1.1-2.7 μm in length and 1.1-1.9 μm in width. Strain S304(T) was an obligately anaerobic heterotroph and sulfur reduction stimulates growth. Growth was observed between 50-65°C (optimum 60°C), pH 6.2-8.0 (optimum pH 7.1), 1.0-6.0% NaCl concentration (optimum 3.0%). The fatty acid composition was C(16:0) (71.4%), C(18:0) (20.9%) and C(18:1) (7.7%). The G + C content of genomic DNA was 40.8 mol%. The 16S rRNA gene sequence analysis indicated that strain S304(T) belonged to the genus Kosmotoga. Based on physiological and phylogenetic features of a new isolate, we propose new species in the genus Kosmotoga: the type strain of Kosmotoga arenicorallina sp. nov is S304(T) (=JCM 15790(T) = DSM22549(T)). Thermococcoides shengliensis 2SM-2(T) is phylogenetically associated with Kosmotoga olearia 14.5.1(T). Based on the phylogenetic relationship between Thermococcoides shengliensis 2SM-2(T) and Kosmotoga olearia 14.5.1(T), we propose the reclassification of Thermococcoides shengliensis as Kosmotoga shengliensis comb. nov. (type strain 2SM-2(T)). In addition, an emended description of the genus Kosmotoga is proposed.

A series of dives was conducted during April/May 2002 in a variety of water masses over the Japan Trench using the remotely-operated vehicle ROV HyperDolphin. The scyphomedusan fauna was catalogued, resulting in the first records of Atolla vanhoeffeni and Atolla russelli from Japanese waters. A new genus and species referable to the family Paraphyllinidae was also recognized. The ulmarid scyphomedusa Poralia rufescens is by far the most common scyphomedusa in these waters. Its distribution was determined by water mass structure and it was not present in subducted Oyashio Current-derived waters occurring within its usual depth range. Temperature and salinity affected its distribution more than dissolved oxygen concentrations. Distributional information, data on the physico-chemical parameters of the water column, and notes on biological associations with scyphomedusae are introduced.

High water temperatures resulted in damage to coral in Japan's Okinawa prefecture during the world wide coral bleaching event of 1998. However Sekisei lagoon, which has a radius of 20 km and is Japan's largest coral reef area (between Ishigaki Island and Iriomote Island in Okinawa Prefecture), suffered damage to only about 30% of its corals. Why was the influence of coral bleaching relatively weak in Sekisei lagoon? Maintenance of water temperatures that were nonstressful to the corals in Sekisei lagoon is probably due to the physical environment's effects on the flow regime. The flow regime in coral reef regions is an important environmental factor affecting the health, growth, distribution, and structure of the corals. The northeastward flowing Kuroshiro current passes offshore of Japan's coral reef region and thus influences water exchange and the transport of coral eggs and larvae. However, many patch reefs are scattered throughout the Sekisei lagoon. And, the existence of patch reef which uncharted has complicated the bottom topography of this lagoon. Therefore, the health, growth, distribution, and structure of the corals including the circulation in Sekisei lagoon is influenced by the small-scale complex bottom topography. Bottom topography data and continuous physical environmental data, such as water flow and water temperature, are currently being measured by JAMSTEC in order to understand the physico-chemical characteristics of the environment from the deep sea (Kuroshima knoll) to shallow water (Sekisei lagoon) in coral reef regions. Recently, water temperature increases over short time periods have occurred, and it is worried what effects they will have on the coral reef ecosystem in the Sekisei lagoon. In this study, we discuss the necessity of bottom topography measurements, using SEABAT8125, in the Sekisei lagoon, including physical environment data.

We estimated relative bubble density and flux based on the ultrasonic echo intensity and the upward velocity. We derived a relational expression between the relative bubble density and the ultrasonic echo intensity, after assuming that the (a)bubbles can be replaced by simple rigid spheres with a constant radius, (b)the radius is enough larger than the wavelength of the incident wave of the acoustic current meter, and (c)the sound absorption by the sea water can be regarded as the constant. At high tide, at erupting state the relative bubble density had large value, while at halting state it had quite small value. At low tide, however, the relative bubble density had almost always positive value, thus the bubbles always were present in the sea water. And the similarity between the relative bubble density and the upward velocity confirmed that the bubbles in the sea water were transported by the fluid discharged from the underwater geyser.

2004年に, 海洋生態・環境研究部が機構の独立行政法人化に伴い, 極限環境生物圏研究センターに所属する海洋生態・環境研究プログラムとして出発して以来, 5年間を経てここで機構の第1期中期計画が終了した. この間, 海洋生物進化研究と海洋生態系変動研究の2本のプロジェクト研究を中心に様々な研究活動を行い, 数多くの成果を得ることができた. 海洋生物進化研究プロジェクトでは, 深海二枚貝であるシマイシロウリガイの共生細菌のゲノムの解読や, 比較ゲノム解析研究, さらに鯨骨生物群集に見出されたイガイ科二枚貝, ヒラノマクラの共生機構研究や, 単細胞真核生物の有孔虫の研究などが行われた. これらは化学合成共生の機構や進化を明らかにするだけではなく, 真核細胞のオルガネラの進化にも共通した問題を含んでいる. 海洋生態系変動研究プロジェクトでは, 中・深層のプランクトン解析から動物プランクトンの現存量, 昼夜での移動や, 生物ポンプとしての役割, そして中・深層に多いクラゲ類の分布や, それと相互作用する甲殻類の様子などが明らかになってきた. さらに将来のプランクトン自働計測技術をめざしてAUV (Autonomous Underwater Vehicle) を開発した. これらは今後グローバルな海洋生態系において重要な研究や技術として発展していくと思われる. 底生生物の生態学的研究では, 底生生物の分布,成長などの研究のほか, 長期ステーションによるシロウリガイの繁殖と環境要因の関係なども研究した. 深海における多様な生物の研究では深海底泥中の原生生物の非常に大きな多様性や, いろいろな分類群における新種の記載や再記載がなされた. これらの研究では地球上にはどのくらい多様な生物が居るか, という大きな問題に今後答えていくことになるであろう. 深海生物の研究は飼育が困難であることから, 深海生物の詳細な研究を行うには障害となっていたが, 生物飼育の工夫がなされるようになり, ずいぶん進展した. 鯨骨も化学合成動物の飼育における基層として大変重要で, 新しい深海動物の飼育技術として使われるようになると思われる. 深海生物については, 日本語では教科書が無かったが, 日本周辺の深海生物の写真を多く利用した深海生物のテキスト「潜水調査船が観た深海生物」を出版した. 海洋生物のデータベースがこのプログラムの最終年である今年になってスタートしたが, このテキストは, その構築にも大いに貢献している. さらに, 将来の深海生物学や海洋生物学を支えてくれるであろう子供たちを対象にした童話も出版した. 本報告では, こうした中期計画の5年間の成果についてとりまとめ, 概説すると同時に, これらのプロジェクト研究の枠を超えて行われた研究についても記述した.