V41B-1368 0800h
Genomics approach to the environmental community of microorganisms
It was indicated by microscopic observation or comparison of 16S rDNA sequence that many extremophiles were surviving in many hydrothermal environments. But it is generally said that over 99% of total microbes are now uncultivable. Thus, we planned to identify uncultivable microbes through direct sequencing of environmental DNA. At first, shotgun plasmid libraries were directly constructed with the DNA molecules prepared from mixed microbes collected from low-temperature hydrothermal water at RM24 in the Southern East Pacific Rise (S-EPR). It was shown that the sequences of some number of clones indicated the similar feature to the intron in eukaryote or tandem repetitive sequence identified in some human familiar diseases. The results indicated that many microorganisms with eukaryotic feature were dominant in low temperature water of S-EPR. Secondly, shotgun plasmid libraries were constructed from the environmental DNA prepared from Beppu hot springs. The ORFs were easily identified all clones determined entire sequence. Thus it can be said that hot springs is good resources for searching novel genes. At last, the mixed microbes isolated from Suiyo seamount were used for construction of shotgun library. The clones in this library contained the ORFs. From some clones in hot spring and Suiyo sample, aminoacyl-tRNA synthatase, which is generally present in all organisms, was isolated by similarity. The phylogenetic analysis of aminoacyl-tRNA synthetase identified indicated that novel and unidentified microorganisms should be present in hot spring or Suiyo seamount. The novel genes identified from Suiyo seamount were also utilized for expression in E. coli. Some gene products were successfully obtained from the E. coli cells as soluble proteins. Some protein indicated the thermostability up to 70_E#8249;C, meaning that the original host cell of this gene should be stable up to the same temperature. Our work indicates that environmental genomics, including the direct cloning, sequencing of environmental DNA and expression of gene identified, is powerful approach to collect novel uncultivable microbes or novel active genes.
V41B-1369 0800h
Bacterial Temperature Adaptation by Molecular Chaperon GroE
Because temperature is one of the major factors influencing bacterial growth and survival, it is of considerable importance to understand how bacteria survive in their natural environment and how they adapt to temperatures outside of their normal growth range. In this respect, bacteria studied to date have been shown to acquire thermo-adaptation to normally lethal temperatures when pre-exposed to a milder, non-lethal heat shock. This phenomenon depends on heat shock proteins, especially the GroE chaperon, which supports the folding of polypeptides. The GroE chaperon consists of GroEL, a homotetradecameric double-ring cylinder composed of ~57 kDa subunits (1), and its co-chaperone GroES, a homoheptameric dome-shaped ring composed of ~10 kDa subunits. Both genes are essential for bacterial growth, and of the induction of GroE by heat shock prevents protein misfolding and aggregation. Therefore, we suspected that GroE plays a role in bacterial thermal adaptation. In the current report, we investigated temperature adaptation of Bacillus subtilis 168 in which the chromosomal groEL was replaced with a psychrophilic or mesophilic groEL gene. We found that temperature adaptation of this strain occurred by novel mutations in highly conserved regions of groEL.
V41B-1370 0800h
Bacterial Discrimination by FISH using Molecular Chaperon GroE
FISH(Fluorescence In Situ hybridization) is a powerful method for the analysis of the phylogenetic classification of microorganism in the environment. In many cases, 16s rRNA sequences of microorganisms are employed as target probe. Here we showed that novel probe was used in FISH in order to discriminate among the bacteria including psychrophile, mesophile, and thermophile. Molecular Chaperon GroE is a best characterized protein based on Escherichia coli and essential for bacterial proliferation. In E. coli, the amount of GroEL protein per cell reaches to about 5% of total cellualr protein at heat-shock response. This response occurred at transcription levels, the amount of groEL mRNA increases at about 10-fold per cell, reaches to 0.4% of total synthesized RNA. Therefore, we considered that groEL gene was employed FISH analysis as a target probe. Moreover, we found that Gly-Gly-Met (GGM) repeats in the carboxy-terminal of GroEL strongly conserved among psychrophile and mesophile, but not thermophile. In this report, we attempted to discriminate among the bacteria including psychrophile, mesophile, and thermophile by FISH using the specific sequence of GroEL as a probe. Furthermore, we proposed the novel phylogenetic trees based on the amino acids sequences of carboxy-terminal of GroEL for bacterial evolution by temperature adaptation.
V41B-1371 0800h
Thermo-resistance Acquisition of A Mesophilic Bacterium with The Aid of Vector Particles Originating from Thermophiles
The present study was aimed to examine whether virus-like particles (VLPs) would be able to transfer and express the thermo-resistance gene of thermophilic microbes in the mesophilic auxotrophic {\it Escherichia coli} AB1157 mutant. A hyper-thermophilic archaea, {\it Thermococcus kodakaraensis} B41, that was isolated from the Suiyo Seamount APSK06 boring core, released particles (KD-VLPs) during culture. Transduction towards recipient {\it E. coli} AB1157 was carried out using KD-VLP as the gene transfer mediator, in order to examine the lethal effect and thermo-resistant gene transfer capability of the particle. The colony forming ability of the cells was examined in 7 $%$ of gelrite supplemented-LB plates (LB-gelrite plates) at 50, 56, and 70 $\deg$C. Regardless of UV irradiation, KD-VLP showed a reduced efficiency of plating (EOP) of recipient viable cell population to ca 65 $%$. Four colonies were formed in LB-gelrite plates at 50 $\deg$C, which were named as KD-E-Trans, and the gene transfer frequency was estimated to be 5.12 $\times$ 10$^{-8}$ cfu/particle. Obtained KD-E-Trans was cultured in LB liquid medium employing the same high temperature conditions. The cells grew 1.6 $\sim$ 6 fold of the inocula in 13 days at all the examined temperatures, and the generation time of the transductants were as follows: ca 28 hours at 50 $\deg$C, ca 73 hours at 56 $\deg$C, ca 266 hours at 70 $\deg$C. Thus, the gene transfer of thermo-resistance to mesophilic {\it E. coli} from another Domain with the aid of KD-VLPs was demonstrated.
V41B-1372 0800h
Improved Method for Direct Detection of Environmental Microorganisms Using an Amplification of 16S rDNA Region
The thermostable proteins or enzymes were expected to be capable to be utilized in many areas of industries. Many thermophilic microorganisms, which possess the thermostable proteins or enzymes, were identified from the extreme environment. However, many unidentified and uncultivable microorganisms are still remaining in the environment on the earth. It is generally said that the cultivable microorganisms are less than 1% of entire microorganisms living in the earth, remaining over 99% are still uncultivable. As an approach to the uncultivable microorganisms, the PCR amplification of 16S rDNA region using primer sets designed from the conserved region has been generally utilized for detection and community analysis of microorganism in the environment. However, the facts, that PCR amplification introduces the mutation in the amplified DNA fragment and efficiency of PCR amplification is depend on the sequences of primer sets, indicated that the improving of PCR analysis was necessary for more correct detection of microorganisms. As the result of evaluation for the quality of DNA polymerases, sequences of primers used for amplification and conditions of PCR amplification, the DNA polymerase, the primer set and the conditions for amplification, which did not amplify the DNA fragment from the DNA contaminated within the DNA polymerase itself, were successfully selected. Also the rate of mutation in the DNA fragment amplified was evaluated using this conditions and the genomic DNA from cultivable microbes as a template. The result indicated the rate of mutation introduced by PCR was approximately 0.1% to 0.125%. The improved method using these conditions and error rate calculated was applied for the analysis of microorganisms in the geothermal environment. The result indicated that four kinds of dominant microorganisms, including both of bacteria and archaea, were alive within soil in the hot spring in Tohoku Area. We would like to apply this improved method to detection of microorganisms with important genes from more other environments.
V41B-1373 0800h
Direct Measurement of Microbial Methane Oxidation at Hydrothermal Vent Ecosystems.
Though methane concentration and isotope composition at hydrothermal vent areas have been extensively investigated, much remains to be learned about methane oxidation by vent microorganisms; microbial methane metabolism may be a quantitatively important component of organic carbon flow in vent ecosystems. We developed a new experiment system and measured microbial methane oxidation at the hydrothermal vent areas (Suiyo Seamount and south Mariana backarc spreading center) directly. The system was constructed by a combined Niskin sampler with Time-series water sampler attached to a manned submersible or a remotely operated vehicle (ROV). At the sea floor, the sea water inside the Niskin sampler was replaced by the hydrothermal fluid using a direct sampling system of hydrothermal vent fluid. Then the Niskin sampler was closed and the microbial methane oxidation experiment started on site. Hydrothermal fluid in the Niskin sampler was sampled at 30 min or 1 hour intervals by the Time-series sampler; microbial activities were stopped by addition of HgCl $_{2}$ solution to each cylinder of the Time-series sampler. On board, the time-series samples were transferred to glass serum bottles immediately; the samples were stored at $4\deg$C until methane analysis at the laboratory. Dissolved methane concentration was measured with an automatic system consisting of a purge and trap apparatus and a gas chromatograph with a flame ionization detector. The in situ methane oxidation rates were 0.039/h and 0.034/h, and methane consumption rates were 25 nM/h and 6.4 nM/h at Suiyo Seamount and south Mariana, respectively. These results suggest that microbial methane oxidation should be an important organic carbon sink in hydrothermal vent ecosystems.
V41B-1374 0800h
Geochemistry of Besshi-type Massive Sulfide Deposit at Makimine in the Shimanto Belt, Southwestern Japan
Many Besshi-type deposits are known to be hosted in the accretionary complexes in southwestern Japan. Most of them occur in the Sambagawa metamorphic belt, but some are also found in other weakly or non-metamorphic accretionary belts. In order to understand the genesis of Besshi-type deposits, geochemical and mineralogical studies were carried out for the ores from Makimine in the northern Shimanto belt, southwestern Japan. The Makimine deposit occurs in the Late Cretaceous Makimine Formation, which is composed of a series of clastic piles and basalts, and metamorphosed up to greenschist facies. Around the deposit, chert is absent and the clastic piles around the basalts were thermally altered. The evidence indicates that the basalts in the formation had been in situ formed in the clastic piles. The massive sulfide ores of lenticular, podiform and rod-shaped are associated closely with the basalt. The orebodies are consisting of pyrite, phrrohotite and chalcopyrite with minor amounts of sphalerite and quartz. The ores are enriched mainly in the chalcophile elements such as Cu, Fe, Cd, Ag, Bi, Zn, In, Te, Co, Mo, Pb, As, Tl and Sb, and depleted in the lithophile elements compared with the average shale. They have higher Cu/Zn and Cu/Pb ratios; lower Ba contents in comparison with those of other massive sulfide deposits. Their chondrite-normalized REE patterns are characterized by negative Ce anomaly, positive Eu anomaly and depletion of heavy-REE. The chemical properties of the ores are similar to the sulfides from modern hydrothermal ore deposits at mid-ocean ridge such as East Pacific Rise and Mid-Atlantic Ridge, especially of the Cu-rich types. These results suggest that the Makimine deposit was formed by deep sea hydrothermal activity in the clastic piles of subduction zone, which is associated with basalt formation of Kula-Pacific ridge. Their unique properties might be due to mode of hydrothermal circulation in the clastic piles. On the basis of bulk-rock compositions and the Pb isotopic ratios of the ores and associated rocks, the detailed formative environment and processes of the Makimine deposit will be discussed.
V41B-1375 0800h
Hydrothermal circulation within modern sediment layer in a shallow submarine volcano, Wakamiko crater, south Kyushu, Japan
A vigorous fumarolic bubble emission from the seafloor has been well known in the submarine Wakamiko crater ($39\deg$39.5$\prime$N, $130\deg$46.5$\prime$E, depth=200m) in Kagoshima Bay, which is located within adjacent to the active volcano Sakurajima. Previous studies of the Wakamiko crater confirmed evidence for high-temperature ($>$$300\deg$C) hydrothermal activity based on occurence of hydrothermal-origin authigenic minerals such as pyrite and barite and hydrothermal petroleum in the surface sediments. During NT03-09 cruise conducted at Dec. 2003 using ROV Hyper-Dolphin (JAMSTEC), however, only gentle fluid shimmering was located at a small mound about one meter in height and three meters in a diameter, where fumarolic bubbling was associated in the vicinity. We found temperature of the mound reached up to $150\deg$C by stabbing a temperature probe (20cm length) into the sediment, and collected a few core samples (up to 30 cm length) to obtain interstitial water samples. Chemical composition of the interstitial waters is well explained by mixing of hydrothermal fluid endmember (Mg=0) and seawater. The silica concentration of the endmember (approx. 5mM) is comparable to quartz solubility at the seafloor pressure and the measured mound temperature. Chemical composition of the shimmering fluid follows the same relationship as the interstitial water, which strongly suggests the hydrothermal fluid ascend within the sediment layer. Their chemical characteristics were (1) Significant lower chloride concentration ($<$300mM) than that of seawater, and enrichment in ammonium and hydrogen sulfide, and (2) negative $\delta$D values and positive $\delta$$^{18}$O values. These are attributed to contribution of meteoric water and hydrothermal interactions within sediment layer. Although not confirmed by fluid chemistry, involvement of magmatic volatiles is implied by occurrence of stibnite and realgar in the mound sediments, which is considered as precipitated during hydrothermal fluid ascend.
V41B-1376 INVITED 0800h
Local Seismicity beneath Suiyo Seamount, an Active Submarine Volcano, on the Izu-Ogasawara (Bonin) Island-arc System
Several ocean bottom seismographic (OBS) observations were carried out to investigate seismic characteristics related to the volcanic and/or hydrothermal activity beneath Suiyo Seamount on the Izu-Ogasawara (Bonin) volcanic front. A preliminary seismic observation for 2 weeks using 4 OBSs in the caldera was carried out in Oct. 2000, and detected several kinds of seismic activities including long period events and seismicity just beneath the seamount. In 2001, we conducted a seismic refraction experiment to obtain a P wavespeed structural model of the upper crust across the seamount. In the 2002 full-dress investigation of the seismicity, we deployed 10 OBSs in and around the caldera of Suiyo Seamount region and observed more than two months from Aug. 5 to Oct. 9. The seismic activity was characterized by dominance of earthquakes with S-P times of 1-2 sec. We could locate 594 events with an RMS residual of P wave travel time of less than 0.2 s. The hypocenters concentrated at depths of 3.5-7.5 km beneath the seamount and revealed a conduit-like shape with a hollow, which indicated a relation to magma conduit. Furthermore, in the only 5 days observation during Dec. 5 to 9, 2003, we also obtained the same pattern of the hypocenter distribution. A remarkable burst detected on Dec. 6, 34 events occurred in 70 minutes, characterized the seismicity. The most events were S-P times of 0.7 s at the stations in the caldera and located just beneath the summit of Suiyo Seamount. A common characteristic in the 2002 and 2003 observation was a seismic gap at a depth around 3 km beneath the seamount. From these observations for resent 4 years, we conclude that rather stable seismic activity related to the magma conduit is maintained beneath the seamount, which may support the long-standing hydrothermal activity of Suiyo Seamount.
V41B-1377 0800h
Temporal Variations in Flow Velocity and Temperature of Hydrothermal Fluids at Suiyo Seamount, Izu-Ogasawara Arc, Western Pacific
The Suiyo Seamount on the volcanic front of the Izu-Bonin (Ogasawara) Arc, western Pacific is a dacitic volcano. There is a hydrothermal field on the floor of the caldera at a depth of 1380 m, where high-temperature fluid is venting through the sediments. A high-temperature hydrothermal system at the Suiyo Seamount has been drilled in June 2001 and in August 2002 using a tethered, submarine rock-drill system (BMS; Benthic Multi-coring System). The BMS produced 10 cores/holes with average depth of 5 meters. Six holes show fluid discharge with temperatures ranging from 9$^{o}$C to 308$^{o}$C. We deployed two Medusa/Gemini (MG) systems on top of cased seafloor boreholes and two Mini-Medusa (MM) systems at areas of warm diffusive flow sites of Suiyo Seamount in August 2002 for about two weeks. These systems are members of the Medusa series of deep sea fluid monitoring systems. The MG and MM systems have been designed for installations directly atop a cased borehole drilled into the seafloor and on the diffuse seafloor, respectively. All data shows strong correlation between fluid temperatures and seawater temperatures. Four systems are located at distances of several tens of meters; however, both synchronized and anti- synchronized temperature fluctuations are frequently observed. The fluid velocities show strong positive correlation with those of temperatures in cases of MG on top of cased seafloor boreholes. It suggests that the fluid is driven by buoyancy through the cased seafloor borehole. However, they show negative correlation in cases of MM on diffusive flow areas. The most prominent feature of all data is the strong semi-diurnal oscillation. This research is funded by Ministry of Education, Science and Technology through Special Coordination Fund "Archaean Park" project.
V41B-1378 0800h
Diversity and distribution of microbes in deep-sea sub-vent systems, using newly designed in situ growth chambers
Subsurface of deep-sea hydrothermal vent environments is one of the most difficult fields on the Earth to approach and collect reliable samples for microbiological study. In our Archaean Park project, we developed in situ incubation instruments to directly collect microbes from sub-vent fields through a drilled borehole. After excavation using a portable submarine driller (BMS) around deep-sea hydrothermal vents in the Suiyo Seamount on the Izu-Bonin Arc (2001, 2002) and the South Mariana (2003), microbial diversity was examined in samples collected from the boreholes, as well as natural vents, using catheter- and column-type in situ growth chambers. In the catheter samples collected from the Suiyo Seamount, several novel phylotypes of microbial SSU rRNA genes were assigned within epsilon-Proteobacteria and hyperthermophile-related Euryarchaea groups. The former novel epsilon group (SSSV-BE1) was also detected in the South Mariana, but they only appeared in the catheter samples collected just below the venting seafloor. These suggest that the group must be significant in warm, shallow and microaerobic sub-vent layers over the sea, at least in the northwest Pacific Ocean. The column-type in situ growth chamber was specially designed for creating and maintaining physico-chemical gradients in a ca. 40-cm-long column situated on an active vent. In Suiyo Seamount samples (vent temp.: ca. 30-100 degree C), a unique vertical profile was found in the diversity of Archaea. At the column bottom, most of the clones were assigned to be members within the lithoautotrophic thermophilic Ignicoccus, while heterotrophic thermophilic Thermococcus were abundant at the column top. Similar vertical profile has also been appeared in the column samples from the South Mariana. Further quantitative population analysis is now under going using these samples. Our approach to the sub-vent biosphere by the combination of drilling and in situ incubation is almost sure to give us important clues to find and simulate microbial community members in such extreme but different subsurface conditions.
V41B-1379 0800h
Molecular ecological analysis of the distribution and diversity of sulfate-reducing prokaryotes and microbes in deep-sea hydrothermal sites of the Suiyo Seamount, Izu-Bonin Arc, and the Mariana Arc-Backarc, Western Pacific
The present study describes the distribution and diversity of sulfate-reducing prokaryotes from the deep-sea hydrothermal vent field at the Suiyo Seamount, Izu-Bonin Arc, and the Mariana Arc-Backarc Western Pacific. We used a PCR-based metabolic molecular ecology approach that targets a conserved region of subunit A and B of the dissimilatory sulfite reductase (DSR) gene and subunit A of the adenosine-5'-phosphosulfate (APS) reductase gene. The DSR genes were obtained from microbes that grew in catheter-type in situ growth chamber deployed for three days on a vent, and from the effluent water of drilled holes at 5 degree C and natural vent fluids at 7 degree C in the Suiyo. The DSR clones were not closely related to cultivated species or environmental clones. Similarly, novel APS clones were obtained from the mat developed at hydrothermal sites in the Mariana. Moreover, samples of microbial communities from the Suiyo were examined using PCR-denaturing gradient gel electrophoresis (DGGE) analysis based on the 16S rRNA gene. The sequence analysis of 16S rRNA gene fragments obtained from the vent-catheter after a three-day incubation revealed the occurrence of bacterial DGGE bands affiliated with the Aquificae, gamma-, and epsilon-Proteobacteria as well as the occurrence of archaeal phylotypes affiliated with the Thermococcales and of a unique Archaeon sequence clustered with Nanoarchaeota. The DGGE bands obtained from drilled holes and natural vent fluids from 7 to 300 degree C were affiliated with the delta-Proteobacteria, genus Thiomicrospira and Pelodictyon. The dominant DGGE bands retrieved from the effluent water of casing pipes at 3 and 4 degree C were closely related to phylotypes obtained from the Arctic Ocean. Our results suggest the presence of microorganisms corresponding to a unique DSR and APS lineage not detected previously from other geothermal environments.
V41B-1380 0800h
Microbial Community in the Hydrothermal System at Suiyo Seamount on the Izu-Bonin Arc
Microbial community in hydrothermal area at seafloor has been analyzed by culture-dependent and culture-independent methods. Hydrothermal vent water and vent chimneys have been analyzed by PCR. Hyperthermophilic microbes have been isolated from these environments. Though the analysis of these samples can provide the window to penetrate the microbial community under the seafloor, more direct analysis is desired for better understanding of the sub-seafloor microbial community In the "Archaean Park Project" supported by Special Coordination Fund, several holes were bored and cased in the crater of the Suiyo Seamount on the Izu-Bonin Arc, Japan (about 1,400 m depth) in 2001 and 2002. Hydrothermal fluids were sampled at various sites of cased holea at the Suiyo Seamount. Bacterial clone analysis of water samples collected from some drilled holes was reported by Nakagawa et al. recently. The fluids were filtered to collect the microbial cells. The DNA was extracted and used to amplify archaeal 16S rDNA fragments by PCR using bacterial specific primers. The PCR fragments were cloned and sequenced. Clone-analysis showed significant variation in bacterial sequences found in these samples. The species-patterns suggested that the contamination of ambient seawater to hydrothermal fluid is low. Difference in the dominant species depending on the location was found, suggesting that the bacterial community at sub-sea floor is not monotonous but has gradual shift from the hydrothermal center to peripheral area. Higher number of chemolithoautotrophe-related clones were recovered from the samples collected at central hydrothermal area. Higher number of heterotrophe-related clones were recovered from the samples collected at peripheral area. Results obtained from South Mariana area will be compared. References Takai et al. Genetics 152: 1285-1297 (1999), Takai et al. Appl. Environ. Microbioi. 67: 3618-3629 (2001), Summit et al. Proc. Natl. Acad. Sci. 98: 2158-2163 (2001), Wery et al. FEMS Microbiology Ecology 41: 105-114 (2002) Nakagawa et al. Appl. Environ. Microbiol. 70: 393-403 (2004)
V41B-1381 0800h
Geochemical studies on the biodiversity and hydrothermal activity; mineralogy, chemistry, and age determination of hydrothermal chimney collected from Suiyo seamount, Izu-Bonin arc
Hydrothermal chimney structure has the steep environmental gradients of temperature, redox potential, pH and chemical concentration, which will provide diverse microhabitats for microbial communities (K.Takai et al. 2001, Hermie J.M. Harmsen et al. 1997). It is important for detailed understanding of the biodiversity to determine the chimney structural environment. Suiyo seamount is located $28.57\deg$N, $140.66\deg$E, where is suitable to compare with the Mid-ocean ridge hydrothermal field, because of few influence of terrestrial sediment. It was reported that the magma chamber below the seamount was very shallow ($\sim$1 km), and high temperature hydrothermal fluid chamber was underlying just below the seafloor sealed with anhydrite and barite. Chimney samples used in this study were collected by Dive 1222-1225 of SHINKAI 2000 (JAMSTEC) in 2000. We measured the chemical composition with neutron activation analysis (NAA) and X-ray fluorescence analysis (XRF), mineral composition with X-ray diffraction analysis (XRD), and the precipitation age measurements ($\sim$200 years) of these chimneys with $\gamma$-ray spectrometry ($^{210}$Pb/Pb method, $^{228}$Th/$^{228}$Ra method, and $^{210}$Pb/$^{226}$Ra method). The mineral composition of the Suiyo seamount chimney were contained barite (BaSO$_{4}$), sphalerite ((Zn,Fe)S), pyrite (FeS$_{2}$), and chalcopyrite (CuFeS$_{2}$) as a major mineral constituents. The chemical composition shows that gold contents in the chimney collected from Suiyo seamount were much higher (maximum 166 ppm) than other hydrothermal field. The chronological study showed that the precipitation ages of sulfide chimney samples (ranged in 37.2-79.6 years before 2002 by $^{210}$Pb/Pb method) were older than barite chimney ((ranged in 2.9-8.2 years before 2002 by $^{228}$Th/$^{228}$Ra method). We will discuss about the process of chimney formation, the temporal variation of the past hydrothermal activity and the difference from other submarine hydrothermal fields (EPR, MAR, Okinawa trough, Loihi seamount).
V41B-1382 0800h
Spatial and volumetric distribution of Quaternary volcanoes and growth rate of the Izu-Bonin Arc <ETH>A trial for the volume estimation by bathymetry -
The Izu-Bonin Arc (IBA), one of an oceanic island arc that was formed by the subduction of the Pacific Plate under the Philippine Sea Plate, which lies south of Japanese Islands from Izu Peninsula down to Iwo-jima island connecting to the Mariana arc. The IBA forms an arcuate structure with its length of almost 1200 km and width of maximum 400 km in the northern segment and is grown up by the magmatic accretion due to the subduction of Pacific and North New Guinea Plates since Eocene Time. The IBA is not a simple and a single arc and is morphologically divided into three segments, North, Central and South, respectively by two major tectonic lines, Aogashima Tectonic Line (ATL) and Sofugan Tectonic Line (STL) based on various kind of geophysical parameters. We report here volcano spacing and volume of volcanic materials of the Quaternary volcanoes (2Ma >) of the IBA based on a new and a high resolution bathymetric map. The volcano spacing along the volcanic front of the IBA has a paired interval in the North Segment and a short regular interval at the northern part and a long interval at the southern part of the South Segment. The Central Segment has no regular spacing. The estimated volume of the volcanic materials has maximum peak on the volcanic front and decreases toward backarc region. The regular spacing in the Southern Segment reflects a little reaction between crust and melts which rise from the upper mantle by a kind of Rayleigh-Taylor Instability. However, melts react with thick crust causes bimodal and caldera forming volcanism both in Central and North segments. The spacing and volume in relation to the other geophysical parameters demonstrate that the IBA has the different evolving stages, from south to north due to the different duration of magma formation that had been caused by partial melting of the mantle wedge mantle by the addition of fluids from the subducting Pacific and North New Guinea Plates since the Eocene time. The growth rate of IBM is higher than that of ordinary island arc but one order lower than that of LIPs such as Ontong java Plateau.
V41B-1383 0800h
Petrochemical Results for Volcanic Rocks recovered from SHINKAI 6500 diving on the Bonin Ridge (27°15'N-28°25'N): submarine extension of Ogasawara forearc volcanism
Four SHINKAI 6500 submersible dives (dive #823 to #826) were performed along the Bonin Ridge escarpment west of Ogasawara (Bonin) Islands in the West Pacific during May 2004, in the hopes of finding exposures of lower crust of the IBM forearc. The Ogasawara Islands are located on the Bonin ridge, exposing 48-40 Ma boninites on Chichi-jima and depleted arc tholeiite lavas of the same age on Haha-jima. These extremely depleted lavas are believed to have been generated when subduction began beneath the Izu-Bonin-Mariana oceanic arc system. Subsequent rifting (35-30 Ma) formed the Bonin Trough and a 350 km long N-S trending eastern escarpment (Bonin Ridge), where we concentrated our dives. We observed lavas and volcaniclastic sequences by the four SHINKAI dives along the escarpment, and 16 fresh basaltic to andesitic lava samples have been recovered. The first three dives appear to have sampled volcanic constructs, of presumed Oligocene age, along the escarpment, whereas the last dive sampled exposures similar to Eocene rocks of the Bonin islands, including nummulitic limestone. The lava samples were analyzed by ICP-MS at Shimane University for 30 incompatible trace elements. All samples show arc-like chemical signatures, including elevated concentrations of LIL elements, depletions in Ta and Nb, and spikes in Pb, Sr, and Li. All samples show modest enrichments in LREE. A lava sample from the northernmost dive #824 is identical with the depleted tholeiite from Haha-jima Islands at the southernmost end of the Bonin Ridge in terms of trace element characteristics. Other lava samples from northern three dives (#823, #824, #825) have tholeiitic affinities with more elevated highly incompatible elements. This suggests derivation of the series of lavas by different degree of partial melting of a similar source mantle. Samples from southernmost dive site #826, immediately northwest of Chichi-jima Islands, are boninites with U-shaped REE patterns and relatively enriched Zr and Hf concentrations. Our new data indicate that Haha-jima type depleted tholeiites may be widespread along the northern part of the escarpment west of the Bonin Ridge, whereas occurrence of boninite is limited to the region adjacent to Chichi-jima Islands. Segmentation of boninite distribution may be related to an eastward bathymetric indentation of the scarp between Chichi-jima and Muko-jima. Temporal relationships between Eocene tholeiites and boninites of the islands and those recovered by diving await the results of dating and further geological investigations.
V41B-1384 0800h
Hf isotope and concentration systematics of the Mariana arc
Negative Hf concentration anomalies are common but little-discussed geochemical features of island arcs. Because both light rare earth elements (LREE) and Hf may be mobile even in `fluid-dominated' island arcs, it is important to relate their isotopic and elemental ratios to models of slab-mantle mixing. We report new Hf isotope and trace element data for K-rich submarine basalts from the Kasuga seamounts located 10-20 km behind the volcanic front of the southern Northern Seamount Province (NSP) of the Mariana arc. These data, when combined with published data for other Mariana samples, span the full range from low-K tholeiites to high-K shoshonites. Rear-arc Kasuga seamounts seamounts of the NSP have lower $^{143}$Nd/$^{144}$Nd and $^{176}$Hf/$^{177}$Hf ratios than arc-front volcanoes of the Mariana Central Island Province (CIP). Within the CIP, Hf concentration anomalies correlate positively with $^{176}$Hf/$^{177}$Hf ratios. Radiogenic Hf and little or no concentration anomalies characterize samples from fluid-dominated volcanoes (Guguan and Maug), whereas samples from sediment-melt dominated volcanoes (Anatahan and Sarigan) have less radiogenic Hf and larger concentration anomalies. Samples from the Kasuga and Hiyoshi seamounts have even larger negative concentration anomalies and less radiogenic Hf, although the two are not always correlated. These data are consistent with mixing between a depleted mantle and a partial melt of subducted sediment that is saturated with trace accessory phases including zircon, rutile, and monazite. A more volcaniclastic source is needed for the NSP than the CIP. Implications of these findings are three-fold. Partial melts of subducting sediment affect the HFSE and REE budgets of even fluid-dominated island arcs. Slab temperatures must be high enough for a peraluminous melt to be present, even where old, cold slabs are subducting. Refractory accessory phases have the potential to become exotic "nuggets" in the convecting mantle, potentially controlling the global budget of the affected elements.
V41B-1385 0800h
Volcanology and Petrochemistry of West Rota Caldera, Southern Mariana Arc
West Rota volcano is a large dormant submarine volcano with a well-developed caldera in the southern Mariana Arc. West Rota was surveyed and dredged during the 2001 Cook 7 expedition and later explored and sampled with the ROV ROPOS, during the Submarine Ring of Fire 2004 expedition. The caldera floor lies approximately 1500 m below sea level and extends 5 km E-W and 8 km N-S. The eastern caldera rim reaches to within 400 m of the sea surface and slope reconstructions indicate that the volcano was subaerial prior to the caldera-forming eruption. Twenty samples collected by dredging, from three locations and eight samples obtained by ROV sampling were studied petrographically and geochemically. In addition to sampling, the ROPOS dive examined the succession of flows in the caldera wall, which record the magmatic evolution of this volcano. The dredged samples, which vary from fresh to intensely altered, range from 50 to 81 weight % SiO$_{2}$. The fresh samples are basalts to rhyolite. Samples from two dredges on the slopes of the volcano consist of fresh basalts, basaltic-andesites and andesites, along with rare rhyolite pumice. Mafic lavas contain olivine and plagioclase and, rare orthopyroxene. Five of the twelve samples dredged from the base of the eastern wall of the caldera contain sanidine and tridymite, which are a result of high temperature hydrothermal alteration. Three of the altered samples are enriched in K$_{2}$O (7 to 8.5 weight %) and the remaining two have 3 weight % K$_{2}$O. The samples collected during the ROV dive were all taken from the caldera floor and the lower eastern wall along a dredge path from the 2001 expedition. The 2004 samples range from 56 to 70 weight % SiO$_{2}$ and are porphyritic basaltic andesites, porphyritic andesites and pyroxene-bearing dacitic pumices. The upper 400 m of the eastern wall of the caldera consists of an uninterrupted vertical sequence of eruptive products. These include andesite flows, pyroclastic flows and finely laminated ash-fall deposits all on the order of 10s of meters thick capped by the final eruptive unit consisting of dacite and rhyolite pumice boulders up to 3 meters in diameter. Work in progress includes Sr isotope and trace element analyses, which will help in the understanding of an apparent increase of SiO$_{2}$ in the eruptives over time.
V41B-1386 0800h
Chemical Characteristics of Plumes above and Around NW-Rota Submarine Volcano: Before and During the March 2004 Eruption
During the March 2004 Ocean Exploration cruise to the Mariana Arc, a small-scale volcanic eruption was observed at the NW Rota-1 submarine volcano by the Canadian ROV ROPOS. CTD tows and casts were conducted above and around the seamount to sample the water for dissolved and particulate chemical species during the eruption. The water column around NW Rota-1 was also sampled in March 2003, providing a baseline for evaluating eruption-induced changes in the chemical composition of the seawater. These investigations mark the first time that water around an erupting underwater volcano has been sampled before and during an eruption. During the 2003 cruise, only an above-summit plume between 400-600 m was observed originating from NW Rota-1. This plume was distinctly hydrothermal, with high values of iron oxides and its associated oxyhdroxides, elemental sulfur, and aluminum in the form of natroalunite. In addition, the natroalunite co-occurs with a silica phase that suggests these Al-rich particles must have formed within the hydrothermal system where magmatic SO2 attacked the host rocks. During the 2004 cruise, prominent plumes were detected both around the flanks and above the summit. The flank plume completely surrounded the volcano from about 700 m to the seafloor (at least 2000 m). Bulk XRF analysis and SEM particle imagery show this plume to consist primarily of glass fragments. This plume may be caused by earthquake tremor associated with the eruption, causing resuspension of eruption debris. The summit plume consisted of a mixture of minerals similar to those sampled during the 2003 cruise, including highly elevated levels of Fe consistent with fresh lava/water interactions and/or release of subsurface rock that has previously interacted with SO2.
V41B-1387 0800h
Sulfur Isotope Geochemistry of Mariana Arc Hydrothermal Systems
Sulfur isotope measurments were performed on H$_{2}$S and SO$_{4}$ in hydrothermal fluids together with elemental sulfur precipitates collected from newly discovered active hydrothermal systems in Mariana Arc. These samples were collected during R/V Thomas G Thompson cruise with ROPOS at March 2004, conducted under Submarine Ring of Fire 2004 project. We report sulfur isotope systematics of these hydrothermal fluids comparing with those from TOTO cauldron in southern Mariana Arc previously studied. The venting fluids from some Mariana Arc hydrothermal systems have remarkably low \delta $^{34}$S(H$_{2}$S) values (-5.9 to -10.0\permil for NW Rota, -3.0 to -6.9\permil for NW Eifuku, -5.5\permil for Kasuga 2) as well as TOTO ( -3.8\permil). Compared with mid-oceanic ridge hydrothermal fluids showing \delta $^{34}$S of -2.3 to + 7.3\permil, these low values suggests that the Mariana Arc and TOTO caldera hydrothermal systems are distinctive in terms of production mechanisms of hydrogen sulfide or source of sulfur. At NW Rota Pit, we found that, venting fluid has higher sulfate concentration (35.4mM) and slightly lower\delta $^{34}$S value (19.0\permil) than ambient seawater (28mM, 21.0\permil). We also confirmed existence of sulfur spherules (\delta $^{34}$S =-5.1\permil). These results suggest disproportionation reaction of the exsolved SO$_{2}$ from a magma body is a predominant mechanism of sulfur species of the hydrothermal system. Extremely low pH of the fluid agrees with production of sulfuric acid by disproportionation.
http://oceanexplorer.noaa.gov/explorations/04fire/welcome.html
V41B-1388 0800h
Epsilon-Proteobacterial Dominance in Microbial Mats Located at the Champagne Hydrothermal Vent Site on NW Eifuku Volcano, Mariana Arc
By far the most extensive hydrothermal vent related microbial mats discovered during the 2004 Ring of Fire cruise were those found at NW Eifuku Volcano located along the Mariana Island Arc. The Champagne Hydrothermal Vent Site located near the summit of NW Eifuku Volcano (1,650 meters below sea level) consists of multiple white smoker chimneys venting highly gaseous fluids (Max temp $\sim$$103\deg$C). Large amounts of liquid carbon dioxide bubbles and clathrates were observed exuding from the seafloor contributing to an extremely low Eh (i.e., highly reducing conditions) and giving the location its name. Luxuriant white flocculent mats were discovered and collected in and around the Champagne Vent Site in April, 2004. Molecular analyses of small subunit ribosomal DNA (SSU rDNA) from these mats using both T-RFLP community fingerprinting and PCR-generated clone library analyses showed that the bacterial community is dominated by $\epsilon$-{\it Proteobacteria} represented by the thiovulum-group along with lesser levels of {\it Thermotogales} represented by the thermotoga-group (as determined using the Ribosomal Database Project). Initial estimates of the relative abundance of phylotypes place the thiovulum-group at 50% and 67%, and the thermotoga-group at 18% and 9%, for T-RFLP and clone library methods, respectively. Phylogenetic analysis of SSU rDNA sequence data also suggests that these most dominant phylotypes are most likely chemoautotrophic and involved in sulfur-cycling. Due to the extreme nature of their habitat, many of these bacteria often grow where no macrofauna are present. However, on the edges of these areas, once sufficient mixing has taken place, abundant macrofauna can be seen vigorously feeding upon these microbial mats. This further demonstrates the transfer of chemosynthetically-derived energy up the food chain supporting large communities of macrofauna. Similar types of microbial mats have been observed at Axial Volcano on the Juan de Fuca Ridge, where they were dominated by a diverse community of $\epsilon$-{\it Proteobacteria} known to both oxidize and reduce multiple sulfur compounds.
V41B-1389 0800h
Hydrothermal circulation system in the central Mariana illustrated by Magnetometoric Resistivity experiments
Hydrothermal vent fields are known to exist on the spreading axis, where sea water penetrates into the crust and upwells through the hydrothermal vents. Understanding of the hydrothermal circulation system is extremely important to reveal the cooling process of the oceanic crust. The thermal structure beneath the hydrothermal vent reflects the extent of underground activity and the convection scale of the hot water. Temperature in the crust can be estimated from the electrical conductivity because the conductivity depends on the water volume, the salinity concentration and the temperature of the sea water in the crust. The Alice Spring Field (18 $^{\circ}$12.9'N, 144 $^{\circ}$42.5'E and 3600m deep), on the spreading axis in the central Mariana Back-Arc Basin, is a suitable site for this purpose. Hydrothermal vent in this field was firstly discovered by Alvin in 1987 (Hawkins et al., 1990). Shinkai6500 also confirmed the hydrothermal activity in 1992 and 1996 (Gamou et al., 1994; Fujikura et al., 1997). In November, 2002, we conducted Magnetometric Resistivity (MMR) survey using R/V Kairei, JAMSTEC in this field. In the MMR method, controlled electric current was applied from a pair of electrodes; one is just beneath the sea surface and the other is close to the seafloor. To record electoromagnetic responses of the crust to the inputed current, we deployed six ocean bottom electromagnetometers (OBEMs), which can measure 3-components of magnetic and electric fields simultaneously. Measurements were conducted at 34 sites around the field, each of which consists of 30 minutes stacking for repeated current signals to keep better S/N ratio. Apparent resistivity is given by a function of amplitudes of magnetic field variation and source-receiver distance. We recovered the data from four OBEMs (two were on the spreading axis and other two were off axis). The plot of magnetic amplitudes to source-receiver distances shows different trend between OBEMs on-axis and off-axis. Therefore, we applied the Occam's inversions (Constable et al., 1987) to estimate 1D conductivity structure separately in these two areas. We obtained similar resistivity at upper part (0--100m) in both the two area, however, the resistivity at 100--300m in the on-axis is lower than that in the off-axis by roughly two orders of magnitude. This indicates that the temperature of crust under 300m depth on-axis is higher than that of off-axis. We will present further discussion on this meeting.
V41B-1390 0800h
Detailed Sidescan Imageries Obtained From the Southern Mariana Trough and the Suiyo Seamount of the Izu-Bonin Arc.
Side-scan-sonar (SSS) is a tool to create 2-dimensional imagery of the seafloor, and sub-bottom-profiler (SBP) is for a cross sectional (vertical) structure beneath the seafloor. These 2 instruments were combined into a compact (portable) package (off-line system) to accommodate into various vehicles such as ROVs and deep-tow frame. We named the system _eDAI-PACK: Deep-sea Acoustic Imaging Package_f. During the cruise TN167 at the back-arc spreading area in the southern Mariana, ROPOS-dive#777 was assigned to do the mapping by DAI-PACK. 2 box survey lines were planned at Fryer site and Yamanaka site on the axial hydrothermal area. Mesotech 971 forward-scanning sonar was used and its record was saved digitally. We were able to process the Mesotech 971 data and the images were plotted on maps. 2 boxes and transit between them were successfully processed using smoothed data of LBL positions. The cruise NT03-14 was carried out at the Suiyo seamount using ROV Hyper-Dolphin -dive#262,#265,#266, with SSBL acoustic positioning system. The ROPOS and the Hyper-Dolphin could have been maintained at the height of 3-5m from the sea-bottom. From the records of ROPOS_fs 7.5 hours, 4 and a half survey lines (East-West direction) were successfully recovered from Box-1. Each survey line was separated by 50m and the half swath range of the SSS was set to 30m to make full coverage of the box 1 and 2. We can recognize the rocks of 1m in size from the mosaic imagery, but the preliminary image is skewed and distorted because the vehicle_fs attitude correction is not quite right yet. Although the SSS transmits 10 pulses per second, attitude sensors of the ROPOS were recorded only one per second, which sometimes makes it difficult to relocate every pulse of the SSS to its true position. At the pre-cruise meeting it was announced that ROPOS would be installed with new navigational/scanning tools, i.e. a doppler sonar and a pencil-beam sonar, which could make the post processing of the SSS data easier. Both of them, however, could not be used during our cruise because of insufficient preparation. The video camera imagery is now being used to correct the vehicle_fs position/attitude data to make better mosaic.
V41B-1391 0800h
In Situ Observations of Dissolved Manganese in Hydrothermal Vent Plumes at Mariana Trough.
We studied for hydrothermal plumes in Mariana Trough by using in situ Mn-Fe analyzers (GAMOS-II). GAMOS-II (Geochemical Anomalies MOnitoring system) is an in-situ chemical analyzer used to detect manganese and/or iron anomalies in neutrally buoyant plumes and to map distributions in bottom seawater over vent fields. During TN167 (ROV ROPOS / R/V Thomas G Thompson) cruise, GAMOS-II measurements were conducted for plume observation at the Yamanaka and Fryer sites. GAMOS-II was attached on the sampling stage of the ROPOS at dive #'777. ROPOS arrived at the bottom at 0:50, and left the bottom at 10:55. Active manganese and temperature anomalies were detected around 2:00 - 5:00 and 7:00 - 11:00, when the ROPOS passed through hydrothermally active areas. The anomaly of temperature and manganese concentration was observed coincidentally, but the relation ship is not consistently proportional. Wide variation in Mn vs. temperature ratio implies diversity between geochemical flux and heat flux depending on the type of venting in the hydrothermal sites. During KH-04-02 Leg2 (AUV r2D4 / R/V Hakuho-Maru) cruise, GAMOS-II measurements were also conducted for plume observation at NW ROTA #1 seamount. GAMOS-II was attached in the AUV r2D4 with CTD. During four successive dives, the fine structure of hydrothermal plumes changed drastically, probably reflecting temporal variation of hydrothermal activity. Continuous sampling by using GAMOS-II was also done successfully. We will also discuss about the data of this continuous sampling.
V41B-1392 0800h
Methane Distribution In Plumes Of The South Mariana Back-arc Spreading Center
In the South Mariana Back-arc Spreading Center, two methane plumes were observed in water column based on analysis of methane in seawater samples collected during the R/V Thompson expeditions in 2003 around water depth of 2,700 m over the Fryer site on the ridge-axis seamount (12\deg57.22N, 143\deg37.16E, depth: 2,850 m). The estimated end-member isotopic compositions of methane in the two plumes are \delta$^{13}C$_{CH4}$ = -5\permil PDB and -50\permil PDB. These values indicated that the two plumes were originated from the different sources. During YK03-09 cruise using the submersible {\it Shinkai 6500} from October to November in 2003, detailed seafloor observation discovered sulfide chimneys emitting black and clear hydrothermal fluid on the off-axis seamount at Pika site (12\deg55.15N, 143\deg36.96E, depth: 2,773 m). The result of analysis of isotopic composition of methane in the hydrothermal fluids recovered from the off-axis hydrothermal vents using WHATS (Water and Hydrothermal {\it Atsuryoku} Tight Sampler) was averaged value of -4\permil PDB (standard deviation = 1\permil PDB, n = 3). Hydrothermal fluids from the Fryer site were also sampled and were measured: average value = -6.7\permil PDB, standard deviation = 0.3\permil PDB, n = 3. During the R/V Thompson expeditions in March 2004 using ROV ROPOS, 11 ROPOS dives and CTD-RMS plume surveys were conducted, and newly discovered a huge hydrothermal structure with active fluid venting at Achaean site on the ridge skirt (12\deg56.37N, 143\deg37.92E, depth: 2,990 m). The \delta$^{13}$C$_{CH4}$ value of the fluid sample from the site using ROCS (Rotary Clean Seawater sampler) was -14.7\permil PDB. Analysis of isotopic composition of methane in the plume samples collected using the CTD-hydrocast at water depth of 2,500 m over the Archaean site showed -45\permil PDB. Source of methane (\delta$^{13}$C$_{CH4}$ = -50\permil PDB), however, in the two plumes of the South Mariana Back-arc Spreading Center has been missing. The \delta$^{13}$C of methane cannot be considered in sediment-starved seafloor hydrothermal fluids as the results from an abiogenic reaction in magma. Alternative explanation would be the secondary stimulated plume of methane that is formed in invertebrate guts of zooplankton swarmed about microbes in the plume, as proposed about a subsurface CH$_{4}$ maximum in the upper oceanic water column. The secondary methane plume may be associated with methane plume without a corresponding enrichment in $^{3}He, observed in the Mariana Trough Back-arc basin at 14\deg N.
V41B-1393 0800h
Characterization of Dissolved Organic Matter from Deep-sea Floor Hydrothermal Vents in South Mariana Backarc Spreading Center
In South Mariana Backarc Spreading Center, a few active hydrothermal fields are located. We investigated a characterization of dissolved organic matter (DOM) from hydrothermal vents in this area, in order to clarify the biosphere beneath deep-sea floor. Hot water sample was collected from a drilled hole (APM01 located in Fryer site, 12$^{o}$ 55.22$^{_f}$N, 143$^{o}$ 37.16$^{_f}$E, depth 2850m) during the ROPOS/TN167A cruise in March 2004. The hole had been drilled during Hakurei-Maru 2 cruise in January 2004. Another hot water sample was collected from a natural black smoker located in Pika site (12$^{o}$ 55.15$^{_f}$N, 143$^{o}$ 36.96$^{_f}$E, depth 2773m) during YK03-09 cruise. In this investigation, we developed a standalone filtration system in order to collect and enrich dissolved organic matter of quite low concentration. This system was designed to be put near hydrothermal vents for at least 24h. This system has an ODS disk (Empore$^{TM}$ High Performance Extraction Disk C18 90mm\phi\) with a pre-filter (Whatman GMF 1 \mu\)m filter paper) to adsorb dilute organics. We collected DOM from the APM01 casing pipe for about 30h (Tmax = 25-30 $^{o}$ C, the estimated volume of filtrated water is max. 300L) using this filtration system. Adsorbed organics were eluted with methanol for 12h twice and toluene once using soxhlet extractor. Recovered amounts of methanol eluents are 72.8mg for APM01, and 89.7mg for the black smoker. Prior to GCMS analysis, we carried out high resolution $^{1}$ H-NMR measurement (400MHz), together with the DOM samples collected from the Suiyo Seamount in July-August 2001 and August 2002. Most of the samples show signals in the region of 3-4 ppm, and the samples from the vents of relatively low temperatures (APM01 and AP04: the natural vent at the Suiyo Seamount, temperature 8-48$^{o}$ C ) show signals also in the region of 0.8-1.6 ppm.
V41B-1394 0800h
Microbial Community in the Hydrothermal System at Southern Mariana Trough
There is unique ecosystem around deep-sea hydrothermal area. Living organisms are supported by chemical free energy provided by the hydrothermal water. The ecosystem is expected to be similar to those in early stage of life history on the earth, when photosynthetic organisms have not emerged. In this study, we have analyzed the microbial diversity in the hydrothermal area at southern Mariana trough. In the "Archaean Park Project" supported by special Coordination Fund, four holes were bored and cased by titanium pipes near hydrothermal vents in the southern Mariana trough in 2004. Hydrothermal fluids were collected from these cased holes and natural vents in this area. Microbial cells were collected by filtering the hydrothermal fluid in situ or in the mother sip. Filters were stored at -80C and used for DNA extraction. Chimneys at this area was also collected and stored at -80C. The filters and chimney samples were crushed and DNA was extracted. DNA samples were used for amplification of 16S rDNA fragments by PCR using archaea specific primers and universal primers. The PCR fragments were cloned and sequenced. These PCR clones of different samples will be compared. We will extend our knowledge about microbiological diversity at Southern Mariana trough to compare the results obtained at other area.
V41B-1395 0800h
Quantitative Population Analysis of Some Groups of Epsilon-Proteobacteria, Using in situ Growth Chamber Samples From Hydrothermal Vents in the South Mariana
To reveal deep-sea hydrothermal microbial ecosystems, we have developed and applied several new sampling systems, e.g., in situ filter samplers and in situ growth chambers. The later enables to incubate and accumulate microbes inside a hydrothermal vent with complex physico-chemical gradients naturally created in a vent flow. Using this system, we have found several novel phylotypes of microbes in the Suiyo Seamount. Among them, two novel groups of epsilon-Proteobacteria (SSSV-BE1 and SSSV-BE2; Higashi et al. FEMS-ME 2004) were assumed to originate from sub-vent fields, mainly at the borehole SH-APSK05. Some of the known epsilon groups, i.e., CorreOs Groups D (the hydrothermal vent type) and Group B (the microbial mat type), were also detected in the same samples. Afterwards, we have further improved in situ growth chambers larger to gain enough amounts of microbial RNA samples for quantitative population analyses. A new chamber system named column-II type was then applied to a natural vent at Fryer site in the Mariana Trough, with temperatures of venting fluids beyond 109 C. Through the 16S rRNA gene clone library analysis, members of the above epsilon-Proteobacteria groups were frequently found in this column-II chamber sample, as well as the Suiyo Seamout samples. So, we tried to estimate population sizes of these epsilons by a quantitative fluorescent dot-blot hybridization (FDBH) technique. First, we newly designed two novel oligonucleotide probes specific to members of the groups D (26 mer) and SSSV-BE1 (23 mer), in which the stringency was checked using soft wares from Ribosomal Database Project II and DDBJ. Total RNA samples, after extracted and purified from the chamber samples, were applied to a nylon membrane filter and hybridized with these two specific probes, as well as Eubacteria, Universal, and some sub-domain/group-specific probes. After the hybridization, resulting fluorescence intensities were quantified, averaged, and compared each other, and then the target microbial population was calculated. Finally, we estimated the relative abundance of these epsilon-Proteobacteria groups in the total Bacteria, and the results implied that more SSSV-BE and group D exist as it goes to the deeper sub-vent. Further examinations of the population, and of whether this phenomenon can be observed commonly such as from the Suiyo Seamount samples, are carried out at the moment.
V41B-1396 0800h
Early History of Island Arcs - Evidence from the Mariana Trench
Among the many problems concerning the initiation and early history of island arcs is the question - what underlies arc plutonic and volcanic series ? Conventional wisdom is that arcs are built on older ocean crust. Their deep roots should include high-Mg eruptions, crystal cumulates complementry to higher-level differentiated lavas, plutonic rocks compositionally equivalent to lavas, and depleted mantle residue complementary to extracted arc magmas. If built on older ocean crust, the "roots" should overlie seafloor sediments, pillows, dikes, etc. (i.e., ophiolites). Probable exposures of deep roots of arcs are rare; exposures such as Tonsina Complex, Alaska and Zambales Range, Luzon are notable for a lack of evidence for subjacent ocean crust. The Zambales shows unmistakeable evidence for continuity from depleted harzburgite/dunite to a thick layered cumulate series of wehrlite,dunite, pyroxenite; these are overlain by norite, gabbro and arc tholeiite basalt. Much of the cumulate series and norite-gabbro has blasto-mylonite texture. These petrologic features suggest upwelling of parental peridotite mantle into a realm of oceanic lithosphere extension. The nascent arc has replaced former ocean crust rather than being built on it. The extensional regime, owing to subduction and seaward trench roll-back, has driven opening of back arc basins, caused forearc rifting, and provided a rift setting for initiation of arc magmatism. Rocks dredged from the Mariana Trench (14 to 18 N) from depths of 9000 to 3000 m, display evidence for near-solidus penetrative deformation that developed higher amphibolite facies mylonites and blasto-mylonites. Rocks include depleted peridotite, pyroxenite, wehrlite, cumulate amphibolite, norite/gabbro, tonalite. High-T metamorphism is shown by equilibrium assemblages of labradorite-bytownite, AL-hornblende, ortho- and clino- pyroxene. Highly deformed homogeneous calcic plagioclase has cross-cutting veins of xenoblastic plagioclase and rare veins of hornblende. Epidote or other An-substitutes are absent except for minor veinlets associated with retrograde talc, tremolite, chlorite. The high-T penetrative deformation and recrystallization are evidence for near-solidus deformation of newly formed arc crust and upper mantle as a consequence of shallow -level crust/mantle extension. Close association of these arc-series rocks with Eocene boninites makes it likely that they all formed at the Palau-Kyushu Ridge and have progressively migrated eastward tracking roll-back of the Mariana Trench.
V41B-1397 0800h
Radiometric Dating of Large Volume Flank Collapses in The Lesser Antilles Arc.
It is now admitted that flank collapses, probably triggered by magmatic inflation and/or gravitational collapses, is a recurrent process of the evolution of the Lesser Antilles Arc volcanoes. Large magnitude debris avalanche deposits have been identified offshore, in the Grenada basin (Deplus et al., 2001; Le Friant et al., 2001). The widest extensions have been observed off the coast of Dominica and St Lucia, with associated volumes up to 20 km3. Another large-scale event, with marine evidences probably covered by sediments and latter flank collapses, has been inferred onland from morphological evidences and characteristic deposits of the Carbets structure in Martinique. We present radiometric dating of these three major events using the K-Ar Cassignol-Gillot technique performed on selected groundmass. Both volcanic formations preceding flank collapses (remnants of the horseshoe shaped structures or basal lava flows) and following landslides (lava domes) have been dated. In the Qualibou depression of St. Lucia, the former structure has been dated at 1096+-16 ka and the collapse constrained by dome emplacement prior to 97+-2 ka (Petit Piton). In Dominica, several structures have been associated with repetitive flank collapse events inferred from marine data (Le Friant et al., 2002). The Plat-Pays event probably occurred after 96+-2 ka. Inside the inherited depression, Scotts Head, which is interpreted as a proximal pluri-kilometric megabloc from the Soufriere avalanche, has been dated at 14+-1 ka, providing an older bound for this event. In Martinique Island, three different domes within the Carbets structure have been dated at 335+-5 ka. Assuming a rapid magma emplacement following pressure release due to deloading, this constrains the age of this high magnitude event. Finally, these results obtained from three of the most voluminous flank collapses provide constraints to estimate the recurrence of these events, which represent one of the major hazards associated with volcanoes of the Lesser Antilles Arc.