Preliminary Report on

KR06-10 Cruise in the

Nankai Trough off Muroto

Aug. 21 – Aug. 25, 2006 Yokosuka - Yokosuka

Masataka Kinoshita (IFREE-JAMSTEC)

And KR06-10 Shipboard Science Party

Acknowledgments

The science party would appreciate the professional skill of the following persons: Captain Mr. Hitoshi Tanaka and KAIREI marine crew for overall support, including ship navigation, KAIKO launching/recovery operation, and ship’s life. Chief ROV Operator Kazuyoshi Hirata and KAIKO Operation Team for KAIKO operation, including hovering during data retrieval at 1173B, and mud removal and bridge plug insertion at 808I. JAMSTEC Marine Operation Department for cruise logistics.

Table of Contents Abstract 1. Introduction 2. Explanatory Notes 3. Dive Report 4. ACORK Operations and Results 5. Preliminary Results

1. Introduction The KR06-10 cruise was carried out as a follow-up study of ACORK hydrogeological observatories installed near the deformation front of Nankai accretionary prism off Muroto (Fig. 1). As well as retrieving the data from two ACORKs, attempt was made to insert a bridge plug into the mouth of ACORK at ODP Hole 808I.

Fig. 1 Index map showing the survey area during the KR06-10 cruise.

Fig. 1.2 Location of ACORK sites 808 and 1173. Stars indicates spicenter of very low frequency events (Ito and Obara, 200#).

Shipboard Scientists

Name Institute Role and Expertise

Masa Kinoshita JAMSTEC, IFREE Chief Scientist / Heat flow

Takafumi Kasaya JAMSTEC, IFREE Electro Magnetics

Keiko Fujino Kyushu University Heat flow

Earl E. Davis

Pacific Geoscience Center,

Geological Survey of Canada ACORK specialist

Robert D. Meldrum

Pacific Geoscience Center,

Geological Survey of Canada ACORK engineer

Audrey Hucks Penn. State University Hydrogeology

Kiyo Kishimoto AIST Sidescan survey

Masato Joshima AIST Sidescan survey

Chiaki Kato JAMSTEC, XBR Microbiology

James Davis Reimer JAMSTEC, XBR Microbiology

Ship and Dive Log Date Aug. 21 Depart from JAMSTEC Pier Aug. 22 KAIKO 7000II Dive#366 (1173) Aug. 24 KAIKO 7000II Dive#367 (808) Aug. 25 Arrive at JAMSTEC Pier

2. Explanatory Notes 2-1. R.V KAIREI

全 長 ： 104.9m

幅 ： 16.0m

喫 水 ： 4.5m

総トン数 ： 4,628 トン

速 力 ： 16.7 ノット

航続距離 ： 約9,600 海里（約17,800km）

主推進機関 ： ディーゼル機関2 基×2,206kW×600rpm

推進システム ： 可変ピッチプロペラ2 軸 バウスラスタ

乗 組 員 ：

60 名

(乗組員 29 名・研究者等 31 名)

建 造 年 ： 1997 年

建造造船所 ： 川崎重工業(株)坂出工場

運航会社 ： 日本海洋事業(株)

2-2. ROV KAIKO 7000II 「かいこう７０００Ⅱ」の主要項目 方 式 ：有索中継機方式、遠隔操作自航

（ランチャー方式）

最大潜航深度 ： 7000m

ランチャー ビークル

長 さ ： 5.2m 2.8m

幅 ： 2.6m 2.5m

高 さ ： 3.2m 2.0m

空 中 重 量 ： 5.8 トン 2.9 トン

水 中 重 量 ： 3.8 トン 0 トン ランチャーの搭載装置

二次ケーブルハンドリング装置

ランチャー／ビークル結合装置

音響探査装置

サイドスキャンソナー

サブボトムプロファイラー

前方障害物探査ソナー

結合監視TV カメラ

音響測位装置

調査観測装置

CTD（塩分・水温・深度計）

ビークルの搭載装置

推進装置（スラスター）

前後方向4 基、左右方向2 基、上下方向4 基（各1PS）

航海装置

白黒TV カメラ（後方）、前方障害物探査ソナー、

方位計、高度計、深度計、フラッシャー、

音響トランスポンダ（2 基）、GPS／アルゴス装置

調査観測装置

広角カラーTV カメラ2 基、3CCD カラーTV カメラ、

デジタルスチルカメラ、

マニピュレータ（1 本、6 自由度、把持力40kgf）、

バスケット（最大10kgf）、照明灯（7 基、合計2,050W）

CTD（塩分・水温・深度計）

2.3. ACORK Two Advanced CORKs (ACORKs) were installed during Leg 196 to provide

long-term in-situ pressure records in the Nankai Trough. The ACORKs were an important advance over the simple CORK hydrogeological observatories successfully installed in many other ODP locations since 1991 (Fig. 2.3.1). Objectives of these long-term installations range from assessing background state of formation fluids to detecting deformation-induced transients to constraining elastic and hydrologic properties of the subsurface from tidal loading signals.

Fig. 2.3.1: Schematic diagram of CORK and Advanced CORK borehole observatories. Exchange between permeable subseafloor formations and the ocean is prevented in the CORK by a seal within the inner casing and by multiple packers that isolate individual screens.

The original CORKs have a single seal at the seafloor and therefore integrate hydrogeologic signals over the entire drilled interval beneath the seal, whereas the ACORK has multiple seals and monitoring intervals in a single borehole to allow pressure measurements at isolated stratigraphic intervals. Prior CORK results and the ACORK concept are described in more detail in a workshop report (Becker and

Davis, 1998) and in several summary articles (e.g., Becker and Davis, 2000; Davis and Becker, 2001; Becker and Davis, 2005).

ACORK at Hole 1173B

The ACORK at ODP Site 1173B has four packers and five screened monitoring intervals. It was successfully installed to 728 meters below seafloor (mbsf). A bridge plug was installed to isolate the deepest screen from pressure at the seafloor via the open casing. During deployment, the bridge plug set prematurely at approximately 466 mbsf. The rig floor did not sense the bridge plug setting, and the drill pipe broke off at the ACORK head. A video inspection at the end of Leg 196 confirmed that the drill pipe broke off precisely at the ACORK head and that the ACORK head suffered no damage, and data show that the bridge plug seated properly. Unfortunately, the broken drill pipe prevented installation of a thermistor cable supplied by JAMSTEC.

Principle observation zones at Site 1173 include oceanic basement below 731 mbsf, the Lower Shikoku Basin formation below the stratigraphic projection of the decollement, and the stratigraphic projection of the decollement within the upper section of the Lower Shikoku Basin formation (Fig. 2.3.2).

Figure F5 (continued)

ACORK installation

0.2 0.6

Ring resistivity(Ωm)

Resistivity wireline(SFLU)

1 1.4 1.8 2.2

Log dataCore data

Log derivedCore data

0 40 80

Gamma ray(gAPI)

Predécollementinterval

0.2 0.6 1

Bridge plug466 mbsf?

354 mbsf

722 mbsf712 mbsf

495 mbsf

439 mbsf

417 mbsf

396 mbsf

374 mbsf

563 mbsf

Packer

Screen

756 mbsf

0

Dep

th (

mbs

f)

100

200

300

400

500

600

700

Clay mineralsfrom XRD (%) Density (g/cm3) Porosity Lo

ggin

g un

it

1

2

3

4

5

Fig. 2.3.2. Logs from Hole 1173B and configuration of the ACORK installed during Leg 196.

ACORK at Hole 808I

The ACORK at Site 808 has two packers and six screens and was intended to penetrate the decollement. Due to poor drilling conditions and failure of the underreamer, actual penetration concluded ~36 meters short of the goal of 964 mbsf. The ACORK head therefore extended 42 meters above the seafloor, and the casing string could not support its own weight. Upon removal of the drill string, the ACORK slowly tipped within seconds. Careful video inspection showed the casing to be bent but not broken. Fortuitously, the ACORK head tipped in the best possible direction—the ACORK rests on its side with logger bay and sample ports facing upward.

Principal observation zones at Site 808 include the Lower Shikoku Basin formation at several depths above the decollement, the overlying Upper Shikoku Basin formation, and the Outer Marginal Trench-Wedge facies near the frontal thrust (Fig. 2.3.3).

Figure F6 (continued)

ACORK installation

Packer

Screen

Dep

th (

mbs

f)

0

100

200

300

400

500

600

700

800

900

1000

1100

1200

1300

Ring

MWD bit

Lithodensity-log derived

Neutron logCore data

480 520 560 1500 2500 3500 0.4 1.2 20 0.4 0.8 0 30 60 90

Chlorinity(mM)

P-wave velocity(m/s)Porosity

Resistivity(Ωm)

RAB-imagedfractures dip (°) Lo

ggin

g un

it/su

buni

t

1

2a

2b

2c

3

4a

4b

4c

1058 mbsf

922 mbsf912 mbsf878 mbsf

833 mbsf

972 mbsf

787 mbsf

371 mbsf

60 mbsf

533 mbsf

Décollement

Fig. 2.3.3. Logs from Hole 808I and configuration of ACORK installed during Leg 196.

The ACORK head is a 30" diameter cylindrical frame fabricated from 3/8" steel

around a section of 11-3/4" casing. In three separate bays, the ACORK head houses: 1) the sensor/logger/underwater-mateable connector assembly, 2) the spool valves and sampling valves and ports, and 3) the three-way pressure sensor valves and geochemical sampling valve and port (Becker and Davis, 2005). At the top of the ACORK head is a 30" reentry cone for drill-bit, sub-casing, or wireline tool delivery systems. References: Becker, K. and Davis, E.E., 2000, Plugging the Seafloor with CORKs, Oceanus, 42, 14-16.

Becker, K., and E.E. Davis, A review of CORK designs and operations during the Ocean Drilling Program, in Proceedings IODP, edited by A.T. Fisher, Urabe, T., Klaus, A., and the Expedition 301 Scientists, Integrated Ocean Drilling Program Management International, Inc., College Station, TX, 2005.

Davis, E.E., and K. Becker, Using ODP boreholes for studying sub-seafloor hydrogeology: results from the first decade of CORK observations, Geoscience Canada, 28, 171-178, 2001.

Mikada, H., Becker, K., Moore, J.C., Klaus, A. et al., 2002, Deformation and fluid flow processes: Logging while drilling and Advanced CORK in the Nankai Trough accretionary prism, Proc. ODP, Init. Repts, 196, in press.

Mikada, H., Kinoshita, M., Becker, K., Davis, E., Meldrum, R., et al., Hydrological and geothermal studies around Nankai Trough (KR02-10 Nankai Trough Cruise Report), JAMSTEC Journal of Deep Sea Research, 22, 125-171, 2003.

3. Dive Report (Hucks and Kinoshita) 3-1. Dive 366 Date: Aug. 22, 2006 Landing Point: 32_14.683’N, 135_01.484’E, 4791m Site Description: Nankai Trough ACORK at Site 1173 Objectives: ACORK data download, Slug test, heat flow, core sampling, SBP Payloads: ROV connector, heat flow probe (SAHF), MBARI sampler, SBP, 2 bags Dive Results: Data downloading was completed in 90 minutes. Team suffered from limited performance of the manipulator. The bag experiment was impossible to conduct. 1 heat flow measurement was made ~100m NW of ACORK, and the result was ~200 mW/m2, consistent with previous result. 2 MBARI core samples were taken. After the mission completed, KAIKO Vehicle suddenly blacked out. Launcher power was recovered soon, so Team could put in the vehicle in place and the whole KAIKO system could be recovered to KAIREI. Dive #366 Log 09:37 KAIKO is launched and begins descent 11:28 KAIKO detaches from launcher 11:42 ACORK confirmed on sonar, 40 meters ahead 11:44 ACORK in view 11:49 right arm grabs ACORK connector 11:54 left arm grabs ACORK head 11:59 connector is in place for data download 12:00 communication started 12:02 clock check 12:03 start of data download 12:08 download restarted due to terminal errors 13:26 download finished 13:27 resetting clock 13:35 setting temporary sampling rate to 10 seconds for 23.5 hours 13:39 connection terminated 13:40 grabbing connector with right arm 13:47 right arm removes connector, and left arm releases ACORK 13:54 connector is stored in KAIKO basket 13:55 moving around ACORK

13:58 examining valves 3 and 4 for possible bag tests 14:03 ACORK leans to east side (finished moving around ACORK) 14:08 landing on seafloor 14:10 M-BARI (yellow) core missed 14:12 M-BARI (yellow) core taken 14:14 M-BARI (yellow) core stored 14:16 landing on seafloor 14:18 M-BARI (red) core taken 14:20 M-BARI (red) core stored 14:21 taking off from seafloor 14:22 landing on seafloor 14:24 taking hold of SAHF 14:26 starting SAHF penetration 14:27 SAHF fully penetrated 14:28 starting SAHF measurement 14:39 removing SAHF 14:39 catching SAHF and starting to pick up 14:40 finished picking up SAHF 14:43 SAHF returned to KAIKO basket 14:44 taking off from seafloor and moving 14:45 vehicle blackout 14:59 starting ascent 16:23 arrival at surface

3-2. Dive 367 Date: Aug. 24, 2006 Landing Point: 32_21.215’N, 134_56.7’E, 4675m Site Description: Nankai Trough ACORK at Site 808

Objectives: ACORK data download, Preparation for bridge plug set, Slug test, heat flow, core sampling, SBP Payloads: ROV connector, heat flow probe (SAHF), MBARI sampler, SBP, 2 bags, Kumade Dive Results: ACORK was located within 30 minutes. Data downloading was completed in 90 minutes. The bag experiment was impossible to conduct, because string for fishing tangled around the valves. As we looked at the mouth of ACORK, we found tube-worm colony there, and we saw some fluid was seeping from inside of ACORK. We decided NOT to deploy the bridge plug during this cruise, because 1) we do not have enough time to complete the mission, and 2) we had better wait until we know the features of the seep fluid. 2 MBARI core samples were taken. After the mission completed, KAIKO Vehicle again suddenly blacked out. Launcher power was recovered soon, so Team could put in the vehicle in place and the whole KAIKO system could be recovered to KAIREI. However, we decided to terminate the dives at this point.

Dive #367 Log 09:24 KAIKO begins descent 11:13 KAIKO detaches from launcher 11:24 confirmation of seafloor on sonar 11:26 Site 808C on sonar (140o) 11:32 heading 50o 11:42 Site 808I on sonar (50o) 11:43 moving along casing toward ACORK head 11:44 arriving at ACORK head 11:47 landing on seafloor 11:50 grabbing connector 11:54 releasing connector 11:55 removing dust cap 11:58 grabbing connector again 12:01 trying to mate connector with ACORK head

12:02 shifting connector 12:04 removing connector, examining locking pin 12:05 trying to mate connector again 12:08 connector is in place 12:11 communication started 12:12 clock check 12:13 start of data download 13:29 data download finished 13:43 resetting clock 13:46 communication ended 13:48 starting to remove connector 13:49 finished removing connector 13:52 connector returned to KAIKO basket 13:55 replaced dust cap on ACORK 13:58 taking off from seafloor and moving 13:59 landing on seafloor 14:04 taking M-BARI (red) core 14:06 storing M-BARI (red) core 14:08 taking off from seafloor and moving 14:11 landing on seafloor 14:13 taking off from seafloor and moving 14:14 landing on seafloor 14:17 taking off from seafloor and moving 14:18 landing on seafloor 14:21 taking off from seafloor and moving 14:22 landing on seafloor 14:37 taking M-BARI (yellow) core 14:39 storing M-BARI (yellow) core 14:41 right arm touches sediment around ACORK head 14:44 taking hold of shovel 14:46 clean up around ACORK head area 14:56 seep observed coming out of ACORK head 15:03 storing shovel, grabbing SAHF 15:06 taking off from seafloor and moving 15:07 landing on seafloor 15:08 taking off from seafloor and moving

15:09 landing on seafloor 15:20 starting SAHF measurement of seep 15:23 holding SAHF in ACORK head area 15:28 finishing SAHF measurement 15:31 SAHF returned to KAIKO basket 15:32 taking off from seafloor and moving 15:45 vehicle connected to launcher 15:47 starting ascent

4. ACORK Operations and Results Site operations Holes 1173A and 808I were visited with Kaiko-7k during dives 366 and 367. During both dives, data were downloaded, clocks were checked and reset, and memory pointers were re-initialized for another epoch of recording. Visual inspection showed no obvious signs of instrument deterioration (with the possible exception of visible corrosion at the upper lip of the Hole 808I ACORK throat). Although the electrical connectors were challenging to mate with the limitations of the Kaiko manipulator, the downloading went smoothly. Over two years had elapsed since the previous visit with Shinkai 6500 in early April, 2004. With the limitation of 9.6 kbaud of the current Kaiko serial communication link, data transmission required more than 1 hour for the 4.0 and 4.6 Mbyte files (see dive logs for details). 38.4 kbaud was available on previous Kaiko trips and is planned for future implementation. Notably, several observations suggested seepage of fluid at Site 808 from the formation below the base of the ACORK casing: 1) A small mound of sediment had formed at the mouth of the ACORK throat, possibly as an accumulation of particulate material from the borehole (Fig. xx), 2) a small colony of worms were seen in this sediment (Fig. yy), and 3) shimmering water emanated from the uppermost rim of the ACORK throat. A temperature measurement was made at this location, but no anomaly was detected above the natural variability of bottom water, constraining any anomaly to be < 0.01 K. Nevertheless, leakage is likely, possibly at a thermally significant rate within the hole itself. The lack of an anomaly at the top of the ACORK is not surprising, given the c. 40 m length of casing lying on the seafloor where efficient heat exchange can take place and the dilution that is bound to be caused by mixing between seepage water and seawater within the uppermost part of the ACORK casing internal diameter. Operations that were planned but not carried out because of lack of time and insufficient dexterity of the Kaiko manipulators included: 1. Installation of the bridge plug in Hole 808I, to provide a seal for the internal diameter of the hole: This is a highly desired objective for a number of reasons, including preventing unnatural drainage and pressure draw-down of the formation, allowing the determination of the natural average pressure state near the level of the decollement, and possibly reducing or eliminating broad-band noise at all screen levels that may be caused by small temperature variations in the i.d. of the ACORK casing (coupled to pressure via thermal expansion).

2. Pressure pulse tests, to allow estimates of hydraulic diffusivity and ACORK-system compliance to be obtained: Plans were to open selected valves briefly (c. 1 minute each separated by approximately 1 hour) to allow screen pressures to drop momentarily to a hydrostatic state. During these operations, c. 1 litre compliant sample bags were to have been installed on the valve sampling ports to allow any fluid production to be detected. Compressibility of the hydraulic system connecting the screens and the ACORK head alone would cause only a fraction of a mlitre to be produced. More water produced quickly would indicate unwanted compressibility somewhere in the system; water produced steadily would indicate higher-than-expected formation permeability. Pressure recovery curves were to be monitored for 1 day at an increased sampling rate of 10 s to provide additional, more quantitative constraints on formation diffusivity. 3. Sensor hydrostatic calibration checks, to constrain pressure sensor drift: While the drift of the pressure sensors was established to be quite low during the initial year of monitoring (tenths of a kPa yr-1), it is desirable to check the rate of drift by occasionally comparing hydrostatic values. This was to be done by simply turning the 3-way pressure sensor valves from their monitoring position (sensors connected to the monitoring lines) to the calibration position (monitoring lines closed, sensors connected to the open ocean). Difficulty with the manipulators precluded doing this at both sites; at Site 808 the problem was exacerbated by fishing line wrapped around the valve handles. 4. Installation of a new-generation pressure-period counter at Site 808, to enhance the fidelity of recording with improved pressure- and time-resolution (50-100 ppb and up to 0.5 Hz, respectively): Without the bridge plug to reduce or eliminate suspected thermally generated noise, and with the constraints imposed by manipulator difficulties and time limitations, it was decided that this installation would not completed. We look forward to being able to complete all of these tasks in the near future. Summary of results The data recovered during this cruise from the ACORK observatory Sites 1173 and 808 bring the total continuous monitoring period to over 5 years. The full records are shown in Fig. 4.1 (1173_all_data_filtered.pdf) and Fig. 4.2 (808_all_data_filtered.pdf). Early parts of the records are complicated by the installation process, but later parts are also far from stable. Some of the temporal variations in pressure are beginning to be understood, such as transient recovery after open-hole or open-screen conditions, elastic response to oceanographic loading, and transient response to seismogenic strain events (with pressure providing a proxy for

volumetric strain during times when conditions remain hydrologically undrained). A particularly clear and interesting example is seen at the time of the off-Kii earthquake sequence in September, 2004, when a series of earthquakes occurred in the Philippine Sea plate near the Nankai trough axis roughly 150 km northeast of the ACORK observatory sites. A swarm of very low frequency earthquakes was stimulated in the adjacent accretionary prism either by the dynamic ground motion of the larger Philippine Sea plate events, or by the regional strain associated with the seismogenic slip. Examples of the strain associated with this event are shown in Fig. 4.3a (Kii_1173_filtered_2_yr.pdf) and Fig. 4.3b (808_unfiltered_kii.pdf). The coseismic and early post-seismic transient response at each of the sites is generally similar to that observed at the time of an aseismic slip event off the Muroto peninsula in June 2003. At Site 1173, the event occurs as a step-wise increase in pressure; at Site 808, a similarly rapid rise is seen, followed soon after by a slower decline, with the amplitude of the rise and the rate of decline varying from screen to screen. Of particular interest is the continuing rise of pressure that occurs at Site 1173 over the course of 200-300 days. It is tempting to conclude that the pressure record has captured continuing slow deformation of the Philippine Sea plate site following the slip that generated the off-Kii intraplate earthquake sequence.

Another notable signal in the new data is high-frequency pressure variations with amplitudes less than 1 kPa at almost every screen. Mikada et al. (2003) noted the existence of these high-frequency variations in earlier ACORK data. The data downloaded during KR06-10 confirms the persistence of these signals. The signals are coherent among all screens (Fig. 4.4) (noise.pdf). Mikada et al. (2003) hypothesized that the signals represent flow in the annulus between the casing and borehole wall. During Dive 367, however, an improved hypothesis emerged to explain the signals: the flow of warmer formation fluid up the unplugged ACORK casing internal diameter may induce small temperature changes that perturb measured pressures by thermal expansion. Only small temperature variations (<<1oC) are required to induce large pressure variations in a closed system.

The visual observations described above support this new explanation for high-frequency pressure variations. On the KAIKO video, shimmering water could be seen emanating from the ACORK head at ODP Site 808, and marine life had colonized the ACORK head, perhaps due to chemical nutrients supplied by fluid seepage there. These suppositions will be investigated with samples recovered from the dive. Also notable in Figure 4.4 (noise.pdf) are the widely ranging amplitudes and phases of tidally-induced pressure oscillations. These amplitudes and phases may

reflect true tidal amplitudes and phases of formation pressure changes due to vertical changes in compressibility of the fluid-filled formation. Alternatively, diminished amplitudes and large phase shifts may be due to slow pressure equilibration rates between the instrument and formation. If the latter is true, instrument compliance, low formation hydraulic diffusivity, or drilling-induced formation damage around the borehole wall may all contribute to retarded pressure equilibration between instrument and formation (Hucks et al., in prep.). Future pressure pulse tests will help determine how the instrument responds to pressure changes in the formation and which of the three factors may limit pressure equilibration rates. Recommendations for future programs We were extremely pleased and impressed by the efficiency and thoroughness of the operations of the crew of the Kairei and the Kaiko team. They were extremely pleasant to work with, were always happy to discuss options for carrying out operations, and exhibited a great deal of talent given the challenges of the shortcomings of the new Kaiko ROV. In the future, we hope that these shortcomings can be dealt with to broaden the range of tasks that can be carried out, to decrease the time required to complete specific tasks, to reduce the risk mechanical, electrical, and hydrologic damage to seafloor instruments, and to decrease the level of frustration experienced by the Kaiko team and the scientific party. Specifically, we would encourage the following improvements: 1. Serial communications speed should be increased back up to at least 38.4 kbaud to decrease the time spent downloading data. Higher rates (e.g., 115.2 kbaud) would be desirable. 2. Switchable power for seafloor instruments (e.g., to save instrument battery power during power-hungry downloads, or to allow downloads to be accomplished after instrument batteries are depleted) would be desirable. 3. Much could be done to improve the capability of the vehicle by having manipulators with longer reach, greater functionality (more degrees of freedom), and better operator controls. Many operations during this program that would have been straight-forward with the previous vehicle were difficult and created unnecessary risks, and other operations that should have been easy were simply not attempted. The manipulators are certainly no match for the abilities of the operators, and much frustration resulted. 4. Greater basket capacity would be highly desirable. In many instances, retrieval and stowage of items was overly time consuming (caused both by lack of easily accessible space, and limited dexterity and scope of the manipulators) and risky (a heat

probe was nearly lost off the basket during ascent). Greater size in both the horizontal dimensions and vertical clearance would allow easier access and provide for larger payload dimensions. The latter could allow heavy instruments to be carried with use of syntactic foam, particularly if the basket (with removable sides to become a shelf) were made sufficiently strong to handle payloads that have large weights in air. References: Hucks, A.L., Flemings, P.B., Elsworth, D., and M. Kinoshita. Hydrologic monitoring in

the Nankai accretionary prism, in preparation.

Trying to dig off the sediment using the Kumade scoop.

Fig. 4.1 (1173_all_data_filtered.pdf

Fig. 4.2 (808_all_data_filtered.pdf)

Fig. 4.3a (Kii_1173_filtered_2_yr.pdf) and 4.3b (808_unfiltered_kii.pdf)

Fig. 4.4 (noise.pdf).

5. Preliminary Results

5-1. Heat flow (Keiko Fujino and Masataka Kinoshita)

Dive366

We brought SAHF#6 and SAHF#7 in this dive. SAH#F6 measured the seafloor temperature and thermal

gradient. We got a thermal gradient near the ODP site of 1173. And SAHF#7 had just measured the

seawater temperature during the dive at KAIKO’s frame.

D366_SAHF#6

SAHF#6 measured a thermal conductivity and seawater temperature of surround area.

Following figures are showed these data.

1.15

1.10

1.05

1.00

Tem

pera

ture

(deg

C)

11:002006/08/22

12:00 13:00 14:00 15:00

Time(sec)

D366SHF01_S6

Tref_stTref_fi

Tcal_or

Tcal_stTcal_fi

11:44

13:3814:26

14:44

11:26

1.20

1.15

1.10

1.05

Tem

pera

ture

(deg

C)

14:202006/08/22

14:25 14:30 14:35 14:40

Time(sec)

D366SHF01_S6

Tref_stTref_fi

Tcal_or

Tcal_stTcal_fi

/0.120.080.040.00

Temperature(degC)

0.6

0.4

0.2

0.0

-0.2

Dep

th (

m)

G=213.83+/-0.58529(mK/m) (5)K=0+/-0(W/m/K)(0)Q=0+/-0(mW/m2)

Thermal gradient:213.83mK/m

Heat flow:209.55mW/m2 (by thermal conductivity of close area, 0.98W/m/K)

D366_SAHF#7

SAHF#7 put on KAIKO’s frame for test of these sensors. During the dive of KAIKO, SAHF#7

took the temperature of seawater and surround area. Because SAHF#7 didn’t be get a touch,

1.15

1.10

1.05

1.00

Tem

pera

ture

(deg

C)

11:002006/08/22

12:00 13:00 14:00 15:00

Time(sec)

D366SHF01_S7

11:38

12:58

13:47

14:47

Tref_st Tref_fiTcal_or

D367

We brought SAHF#6 and SAHF#8 in this dive. SAH#F6 measured the seawater temperature near the

mouth of 808I. SAHF#8 tested the heat pulse for conductivity measurement and measured temperature of

surround’s seawater during dive. We found a shimmering just side of the 808I’s mouth Then SAHF#6

measured the temperature at 15:20, but we couldn’t get the characteristic temperature.

All date show the following figures.

12:08~13:49 During data downloading

12:11 Heat pluse test (SAHF8)

12:57 left hand of manipulator test

14:11 Moved to mouth of A-CORK

15:20 Started to measure the temperature of shimmering

1.06

1.04

1.02

1.00

0.98

Tem

pera

ture

(deg

C)

11:002006/08/24

12:00 13:00 14:00 15:00 16:00

Time(sec)

D367S6

Tref_stTref_fiTcal_or

Temp0 Temp1 Temp2 Temp3 Temp4

12:10 12:58 15:20

1.20

1.18

1.16

1.14

Tem

pera

ture

(deg

C)

11:002006/08/24

12:00 13:00 14:00 15:00 16:00

Time(sec)

D367S8.tem

Tref_stTref_fiTcal_or

12:11

12:58

14:11

15:20

Temperature at shimmering from ACORK head

During dive 368 at ACORK808, we saw shimmering water coming out from the

inner wall of ACORK head. Thus we attempted a temperature measurement using our heat

flow probe (Fig. ##). Measurements were made from 15:22 to 15:28. Fig. ## shows the

temperature data vs. time. Although the flow rate looked as fast as a several cm per second,

no significant thermal anomalies were detected. This could either be because no

temperature sensors were within the flow (sensor interval is 11 cm), or because the fluid is

already cooled down after a long trip within the pipe.

5.2 Subbottom profiling

Kiyoyuki Kisimoto, Masato Joushima, Kiyokazu Nishimura Geological Survey of Japan, AIST

Introduction Side-scan-sonar (SSS) is a tool to create 2-dimensional imagery of the seafloor, and sub-bottom-profiler (SBP) is used to make a cross sectional (vertical) structure of the sedimentary layers beneath the seafloor. These two instruments were combined and integrated into a compact (portable) package system (off-line system) to accommodate into various vehicles. We named the system ‘DAI-PACK: Deep-sea Acoustic Imaging Package’. During the cruise KR06-10, only subbottom profiling function of the DAI-PACK was used. We have successfully recovered the SBP data from both dives; KAIKO-dive#366 on Aug. 22rd and dive#367 on Aug. 24th

Preliminary result For these two dives KAIKO’s operational main target is to come back to the ODP drilling stations with the A-CORK system and to recover the long-term geophysical data records. SSS mapping was exempted from the dives, because the SSS sensor would be an obstacle for the operation of the data recovery from the standing casing with the A-CORK. So SSS survey is postponed to the third dive or later. As the third and further dives were canceled in the end because of the system trouble of the KAIKO, the SSS could not be used in this cruise. On the other hand, the SBP were recorded in rather good condition from the onboard quick inspection. Setting for DC gain is 20db, BT gain is 0bd, shift range is 0m, and range is 20m. Fairly good sub-bottom records were obtained for about 30 minutes, for each dive. During the dive the KAIKO covered the distances of 40m for dive#366, 100m for dive#367. Fig.5-2-1 and Fig.5-2-2 show the first and end parts of profiles of dive#366, and Fig.5-2-3 and Fig.5-2-4 show those of dive#367. Final profile will be produced after the computer-intensive processing on land. A simple comparison of SBP data with the porosity profile measured for ODP core samples at Hole 1173A (Fig. 5-2-5).

Fig.5-2-1 The first part of SBP after KAIKO reach the bottom in dive#366. Vertical and horizontal ratio is approximately 1:1 under the assumption of KAIKO’s speed; 0.5 knot.

Fig.5-2-2 The last part of SBP before KAIKO left the bottom in dive#366. Other condition is same as Fig.5-2-1.

Fig.5-2-3 The first part of SBP after KAIKO reach the bottom in dive#367. Other condition is same as Fig.5-2-1.

Fig.5-2-4 The last part of SBP before KAIKO left the bottom in dive#367. Other condition is same as Fig.5-2-1.

Fig.5-2-5 Sub-bottom sedimentary section obtained by DAI-PACK (AIST) Sub-Bottom Profiler at 1173 site (dive 366). Vertical full scale is 20m. Porosity profile obtained from ODP core at Hole 1173A (MAD data) is overlain with the same vertical scale.

5-3. Biology Purpose: The purpose of this study is to understand the microbial diversity of the Nankai Trough and its relation with the geological settings. We are going analyze the microbial community structure of the sediments from the deepest Nankai Trough bottom at the front of the accretionary prism at a depth of 4,800 m, and compare the community structures with our previous results (indicated below) at shallower depths in the cold seep sediments. (CK)

Until recently, no zoanthids (encrusting anemones, Order Zoantharia) had been described from any chemosynthetic environment. However, numerous individuals of an unidentified sediment-encrusted zoanthid-like species were observed and sampled during Shinkai 6500 deep-sea submersible dive #884 (June 18, 2005) at a methane cold seep (depth=3259m) off Muroto at the Nankai Trough, Japan (32°34.945'N, 134°41.545'E). Unlike previously described deep-sea zoanthids, Abyssoanthus nankaiensis, gen. et sp. nov. (Abyssoanthidae fam. nov.) is non-colonial, free-living (non-commensal), and uniquely is found on mudstone in the vicinity of a methane cold seep. We hope to observe and collect more samples of Abyssoanthus nankaiensis during this study. Even the lack of Abyssoanthus nankaiensis during this dive will give us more information on its distribution. (JDR) Back ground: Microbial community analyses of the Nankai Trough cold-seep sediment. The Nankai Trough is the subduction margin between the Shikoku Basin (Philippine Sea plate) and the South-West Honshu arc (Eurasian plate) at 4 cm/yr. The current accretionary prism is building from the trench axis and increasing in thickness landward. Several seismic profiles provide excellent images of this prism formation. The Cretaceous to Tertiary Shimanto Belt is exposed from the Ryukyu arc to the middle of the Honshu arc. The subducting oceanic plate beneath the Shikoku Basin has spread by 15 Ma. Much geological, geophysical and geochemical data have been accumulated in this regard and are currently available for study (Kuramoto et al., 2001; Park et al., 2002; Kodaira et al., 2004). The Nankai Trough is also one of the areas where cold-seepage has been thoroughly investigated. Since 1984, the French-Japanese KAIKO Project has found several cold-seep sites in the accretionary prism by means of submersibles (Le Pichon et al., 1987). During dive surveys, chemosynthesis- based biological communities served as useful markers for mapping seep sites because

anomalies of temperature and geochemistry in cold-seeps are more rarely detected than those in hydrothermal areas (Le Pichon et al., 1987). Gamo et al. (1994) reported that there might be a drastic change in pore water chemistry between the interior and exterior of Calyptogena communities, because the sedimentary pore water recovered only 0.3 m from the margin of the community showed little indication of in situ sulfate reduction. They also confirmed that surface sediment temperature is higher inside the Calyptogena community than on the outside. Calyptogena is a bivalve associated with sulfur oxidizing (SOx) endosymbiont bacteria living in such environments and researchers have used its communities as markers to investigate the cold-seep environments in the Nankai Trough (Ohta and Laubier, 1987; Ashi, 1997). The description of Calyptogena species and their biogeographical properties were reviewed recently by Kojima et al. (2004). In the Japan Trench cold-seep environments, more abundant seep-microbial communities were identified at deeper depths, where no accretionary prism structures were identified, and this suggested that the deepest depths of the trench could be more dynamic in the seep activity compared to the shallower land slope (Arakawa et al., 2005). To study the different cold-seep microbial ecosystems present between the Japan Trench land slope and the Nankai Trough, the microbial diversity of Nankai Trough cold-seep sites at different depths is described below and the correlation between the microbial communities and the geological setting is discussed.

We identified complete cold-seep microbial communities (AOM systems involving SRB-ANME consortia) only in the shallowest cold-seep sediments from the NT06 site at a depth of 615 m, as shown in following Fig.5-3-1 However, we found wide spread Calyptogena communities at the NT06 site but only a few Calyptogena colonies at the other two deeper sites, NT20 and NT33 sites at depths of 2,048 m and 3,310 m, respectively (Arakawa et al., 2006).

NT06

NT20

NT33

A

γ Ukδ(SRB)γ(SYM) γ(SYM)

ε

NT06

NT20

NT33

B

ANME2c

ANME2a

Met

MG1

Fig.5-3-1 T-RFLP profiles of A: bacterial and B: archaeal community structures of the

NT06, NT20, and NT33 sites. γ, δ and ε indicate the corresponding Proteobacterial groups, and, SRB and SYM indicate sulfate reducing bacteria and symbiotic related bacteria, respectively. Met and MG1 indicate methanogenic archaea and crenarchaeota marine group 1, respectively. Uk; unknown. The length of fragments (x-axis) and relative fluorescence intensity of peaks (y-axis) are also displayed.

These observations, including the current results, indicated that the cold-seep activity of the NT06 site could be higher than at the NT20 and NT33 sites. Basically, cold-seep activity might correspond to the existence of active faults and related geological settings (Kuramoto et al., 2001; Okamura et al., 2002). Thus, our results suggested that the NT06 site could contain more active geological settings than the other two deeper sites. In the case of the Japan Trench, we have reported that more abundant microbial communities commonly identified in cold-seep sediments are found at the deepest depths of the trench (Arakawa et al., 2005), which could be points for fast plate subduction (about 12 cm/yr) by the Pacific Ocean plate into the North American plate. The Nankai Trough is a slower plate of subduction (4 cm/yr) for the Philippine Sea plate into the Eurasian plate (Kuramoto et al., 2001) and the resulting accretionary prism is built from the trench axis and increases in thickness landward. There is a difference in the geological setting of the Japan Trench compared to the Nankai Trough since no accretionary prism structure was identified in the Japan Trench. Several active faults have been identified in the prism structures by seismic imaging profiles (Park et al., 2002; Kodaira et al., 2004). Thus, it is possible that strong cold-seep activity might occur even in the shallower water depths on the prism structures. The NT06 site could be one such area because of the numerous Calyptogena colonies observed there (Kuramoto and Joshima, 1998; Arakawa et al., 2006). It is interesting that complete cold-seep microbial structures (AOM systems) are identified at the shallower depths on the accretionary prism structure in the Nankai Trough while these were identified in deeper sediments in the Japan Trench lacking prism structures.

In conclusion, the current study concerning the microbial diversity of the Nankai Trough cold-seep sediments at different depths suggests a relationship between seep microbial diversity and acceretionary prism structures. This might be an important observation which suggests a correspondence between cold-seep microbial communities and acceretionary prism structures. (CK) Novel zoanthids at the Nankai Trough The Order Zoantharia (=Zoanthiniaria, Zoanthidea) is found worldwide in most marine

environments. Zoanthids are characterized by the presence of two rows of tentacles and one

siphonoglyph, with the majority of species described thus far being colonial and encrusted with sand

and/or other detritus. Despite such conspicuous morphological characteristics, Zoantharia remains a

poorly described, understood and inventoried group. Until recently, Zoantharia was divided into two

suborders, Macrocnemina and Brachycnemina, based on the organization of septa (Haddon and

Shackleton 1891). Septa data are only obtainable by cross-sections, which are unusually difficult to

obtain from small encrusted zoanthids. However, Sinniger et al. (2005) showed that based on

molecular data these two suborders are invalid taxonomic groupings, with Macrocnemina being

paraphyletic. Thus, currently, no single morphological characteristic can be reliably used to identify

zoanthid specimens. However, recent work combining both molecular and morphological techniques

has begun to bring taxonomic order to some groups of zoanthids (Sinniger et al. 2005, Reimer et al.

2004, 2006).

Deep-sea zoanthids have been reported worldwide at depths of up to 5000m (reviewed in

Ryland et al., 2000), and all deep-sea zoanthids identified until now have been characterized as

belonging to the genus Epizoanthus (family Epizoanthidae). Both shallow water and deep-sea

Epizoanthus species have been characterized to generally be; 1) azooxanthellate (although

zooxanthellate species exist), 2) epizoic on a wide variety of substrate organisms (including

mollusks, pagurid crabs [Muirhead et al. 1986], and hyalonematid glass sponges [Beaulieu 2001])

(excepting non-commensal species such as E. couchii and E. paxi), and 3) colonial, with individual

polyps connected by a stolon or coenenchyme.

During a recent Shinkai 6500 deep-sea submersible dive (Dive #884, June 18, 2005) at the Nankai Trough off Japan (32°34.945'N, 134°41.545'E), numerous polyps of a sediment-encrusted Zoantharia-like species were discovered on blocks of mudstone at 3259 m. Unlike most previously reported deep-sea Zoantharia species of the family Epizoanthidae, observed specimens were non-colonial and free-living, and also uniquely inhabited a methane cold-seep chemosynthetic environment. Specimens were collected and compared morphologically and genetically (utilizing mitochondrial 16S rDNA and cytochrome oxidase c subunit I (COI) DNA and nuclear 5.8S-rDNA markers) to samples from the other described families in the order Zoantharia: Epizoanthidae, Parazoanthidae, Sphenopidae, and Zoanthidae. As ecological, morphological, and molecular characteristics were all significantly different from known families in the order Zoantharia, our specimens were attributed to a new family, new genus, and new species. Observed novel characteristics of Abyssoanthus nankaiensis gen. et sp. nov. (Abyssoanthidae fam. nov.) are discussed in relation to other families in the order Zoantharia. Based on morphological characteristics and obtained genetic sequences, the family Abyssoanthidae is the first zoanthid group described from a chemosynthetic

ecosystem. (JDR)

Fig.5-3-2 – Abyssoanthus nankaiensis sp. nov. polyps on mudstone (m), showing several individual closed polyps. Encrusted sediment is evident on the polyp surface. White bar=1 mm, o= oral opening/oral end, a=aboral end.

Fig.5-3-3 - Maximum likelihood tree of obtained mitochondrial cytochrome oxidase c subunit I sequences. Values at branches represent ML and NJ bootstrap probability,

respectively (>50%). Methods: The MBARI core sediments were obtained by means of the ROV, “Kaiko 7KII”, during Dive#366 and #367 during the cruise KR06-10 (PI: M. Kinoshita) at ODP sites 1173B and 808I in the Nankai Trough, off Muroto, at the front of the accretionary prism, respectively. The sediments were sampled at every 2.5 or 5 cm depth, and environmental DNA was extracted directly from the divided sediments samples using an Ultra Clean soil DNA kit (MO-Bio Lab. Co.). Terminal restriction fragment length polymorphism (t-RFLP) of the microbial 16S ribosomal RNA genes analysis will be performed. (CK)

No Abyssoanthus or other zoanthids were sampled during the cruise. Other samples were preserved in 99.5% ethanol for future DNA analyses, or frozen at –80°C. (JDR) Plenary results: The divided sediment samples (see the sample list section) were ready for DNA extraction, and stored them in the liquid nitrogen tank. T-RFLP analysis will be performed, and some of the DNA will be analyzed by the cloning and sequencing in the JAMSTEC laboratory. From dive #367, we observed a polychaete community and swaying water next to the oxygenated iron materials at the laying tower (ACORK station) of site 808I. The relation between the animal community, oxygenated iron materials and swaying water is currently unknown, but such a correlation would be highly unique. Microbial analyses may answer whether the polychaete community exists due to the iron oxidizing and/or swaying water come from the deep sediment. (CK)

No samples of Abyssoanthus or any other zoanthid were collected during the cruise. However, the lack of specimens at non-cold seep sites will help us to characterize the distribution of this novel family better in the future. However, numerous specimens of polychaetes, small tubeworms, small shrimp, and three squat lobsters were obtained during dive 367 as well as from the covering and ropes attached to the Pop-up Heat Flow Instrument (PHF). For sample information, please see the attached sample list and photographs. (JDR) References: (CK) 1. Arakawa, S., M. Mori, L. Li, Y. Nogi, T. Sato, Y. Yoshida, R. Usami, and C. Kato.

2005. Cold-seep microbial communities are more abundant at deeper depths in the

Japan Trench land slope. J. Jpn. Soc. Extremophiles 4:50-55. 2. Arakawa, S., T. Sato, Y. Yoshida, R. Usami, and C. Kato. 2006. Comparison of the

microbial diversity in cold-seep sediments from the different water depths in the Nankai Trough. J. Gen. Appl. Microbiol. 52:47-54.

3. Ashi, J. 1997. Distribution of cold seepage at the fault scarp of the eastern Nankai accretionary prism. JAMSTEC J. Deep Sea Res. 13:495-501.

4. Gamo, T., J. Ishibashi, K. Shitashima, T. Nakatsuka, U. Tsunogai, T. Masuzawa, H. Sakai, and K. Mitsuzawa. 1994. Chemical characteristics of cold seepage at the eastern Nankai Trough accretionary prism (KAIKO-TOKAI Program): a preliminary report of the dive 113 of “Shinkai 6500”. JAMSTEC J. Deep Sea Res. 10:343-352.

5. Kodaira, S., T. Iidaka, A. Kato, J. O. Park, T. Iwasaki, and Y. Kaneda. 2004. High pore fluid pressure may cause silent slip in the Nankai Trough. Science 304:1295-1298.

6. Kojima, S., K. Fujikura, and T. Okutani. 2004. Multiple trans-Pacific migrations of deep-sea vent/seep-endemic bivalves in the family Vesicomyidae. Mol. Phylogen. Evol. 32:396-406.

7. Kuramoto, S., and M. Joshima. 1998. Precise gravity measurements for gas hydrate layer. JAMSTEC J. Deep Sea Res. 14:371-377.

8. Kuramoto, S., J. Ashi, J. Greinert, S. Gulic, T. Ishimura, S. Morita, K. Nakamura, M. Okada, T. Okamoto, D. Rickert, S. Saiyo, E. Suess, U. Tsunogai, and T. Tomosugi. 2001. Surface observations of subduction related mud volcanoes and large thrust sheets in the Nankai subduction margin; Report on YK00-10 and YK01-04 cruises. JAMSTEC J. Deep Sea Res. 19:131-139.

9. Le Pichon, X., T. Iiyama, J. Boulegue, J. Charvet, M. Faure, K. Kano, S. Lallemant, H. Okada, C. Rangin, A. Taira, T. Urabe, and S. Uyeda. 1987. Nankai Trough and Zenisu Ridge: A deep-sea submersible survey. Earth Planet Sci. Lett. 83:285-299.

10. Ohta, S., and L. Laubier. 1987. Deep biological communities in the subduction zone of Japan from bottom photographs taken during “Nautile” dives in the Kaiko project. Earth Planet Sci. Lett. 83:329-342.

11. Okamura, Y., K. Satake, A. Takeuchi, T. Gamo, C. Kato, Y. Sasayama, F. Nakayama, K. Ikehara, and T. Kodera. 2002. Tectonic, geochemical and biological studies in the eastern margin of the Japan Sea –Preliminary results of Yokosuka/Shinkai 6500 YK01-06 Cruise–. JAMSTEC J. Deep Sea Res. 20:77-114.

12. Park, J. O., T. Tsuru, S. Kodaira, P. R. Cummins, and Y. Kaneda. 2002. Splay fault branching along the Nankai subduction zone. Science 297:1157-1160.

(JDR)

1. Beaulieu, S.E. (2001). Life on glass houses: sponge stalk communities in the deep sea. Marine

Biology 138, 803-817.

2. Haddon, A.C., and Shackleton, A.M. (1891). Reports on the zoological collections made in Torres

Strait by Professor A.C. Haddon, 1888-1889. Actinae: I. Zoantheae. Scientific Transactions of the

Royal Dublin Society 4, 673-701.

3. Muirhead, A., Tyler, P.A., and Thurston, M.H. (1986). Reproductive biology and growth of the

genus Epizoanthus (Zoanthidea) from the north-east Atlantic. Journal of the Marine Biology

Association of the United Kingdom 66, 131-143.

4. Reimer, J.D., Ono, S., Iwama, A., Tsukahara, J., Takishita, K., and Maruyama, T. (2006).

Morphological and Molecular Revision of Zoanthus (Anthozoa: Hexacorallia) From Southwestern

Japan With Description of Two New Species. Zoological Science 23, 261-275

5. Reimer, J.D., Ono, S., Fujiwara, Y., Takishita, K., and Tsukahara, J. (2004). Reconsidering

Zoanthus spp. diversity: molecular evidence of conspecificity within four previously presumed

species. Zoological Science 21, 517-525.

6. Reimer, J.D., Ono, S., Takishita, K., Tsukahara, J., and Maruyama, T. (2006). Molecular evidence

suggesting species in the zoanthid genera Palythoa and Protopalythoa (Anthozoa: Hexacorallia) are

congeneric. Zoological Science 23, 87-94.

7. Ryland, J.S., de Putron, S., Scheltema, R.S., Chimonides, P.J., and Zhadan, D.G. (2000). Semper’s

(zoanthid) larvae: pelagic life, parentage and other problems. Hydrobiologia 440, 191-198.

Sinniger, F., Montoya-Burgess, J.I., Chevaldonne, P., and Pawlowski, J. (2005). Phylogeny of the 8. order Zoantharia (Anthozoa, Hexacorallia) based on mitochondrial ribosomal genes. Marine Biology 147, 1121-1128.

Second core sampling at dive 366 (Site 1173).

First core sampling by A-CORK 808 during dive 367.

Second core sampling at Dive 367.

5-4. Long-term Temperature Monitoring 5-4-1. Monitoring of sediment temperature profile

We recovered a pop-up heat flow instrument (PHF) on August 23 (Table 5-4-1). It

was deployed on the KT-05-19 cruise of R/V Tansei-maru in August, 2005.

We first measured the slant range between the ship and the instrument using

acoustic pulses at the deployment location reported in the KT-05-19 cruise log and found

that the instrument was about 2 km apart from the reported location. For estimating the

real position of the instrument, we made slant range measurements at two other locations.

The ship then moved to the estimated position and an acoustic command was sent to

activate the release unit of the PHF. The instrument reached the sea surface 53 minutes

after the command and was successfully recovered (Fig. 5-4-1).

The PHF recorded temperature variations in the upper 2 m of surface sediment for

375 days. It is the longest record obtained with a pop-up type instrument. The bottom

water temperature was monitored for the same period by the small water temperature

recorder attached to the frame.

The bottom water temperature variation (Fig. 5-4-2) at this station (PHF-1) is similar to

those recorded in the Kumano Trough in the last five years. The variation seems to have a

dominant period of around 200 days, though it also contains much higher frequency

components.

Fig. 5-4-3 is a plot of the temperatures in the sediment after correction for sensor

characteristics based on the temperatures recorded just before penetration into the

sediment. It clearly shows features of thermal diffusion; the amplitude of temperature

variation decreases as the depth increases, the phase of the variation shifts with the depth,

and the high frequency components are filtered out as the variation penetrates through

sediment. Using this temperature record, we will examine if there is any non-conductive

(advective) component in the heat transfer process in the surface sediment. We will then

remove the effect of the bottom water temperature variation to determine the undisturbed

temperature gradient and heat flow at this station.

5-4-2. Failure in recovery of the PPT

We attempted to recover a pop-up pore pressure and temperature instrument

(PPT) on August 23. The acoustic command for releasing the weight was sent from the ship

repeatedly, but the PPT did not leave the sea floor. Judging from the response of the

instrument to the command, the releaser of the PPT was activated but could not release the

weight due to some problem with the mechanical structure of instrument. Or the PPT lost

a part of its buoyancy since some of the glass spheres had been broken. We will try to

recover the instrument in different ways (e.g. using ROVs or other vehicles).

Table 5-4-1. Monitoring of sediment temperature profile

Station Deployment Recovery Coordinates Water depth (m)

PHF-1 Aug. 13, 2005 Aug. 23, 2006 33°28.0’N, 136°35.0’E

2080

Fig. 5-4-1. Recovery of a pop-up heat flow instrument (PHF).

1.80

1.85

1.90

1.95

2.00

2.05

2.10

2.15

2.20

8/1/2005 10/1/2005 12/1/2005 2/1/2006 4/1/2006 6/1/2006 8/1/2006 10/1/2006

Bottom Water Temperature

Date

Tem

pera

ture

(°C

)

Fig. 5-4-2. Bottom water temperature record at PWT-1.

1.90

1.95

2.00

2.05

2.10

2.15

8/1/2005 10/1/2005 12/1/2005 2/1/2006 4/1/2006 6/1/2006 8/1/2006 10/1/2006

Sediment Temperature

ch1ch2ch3ch4ch5ch6ch7

Tem

pera

ture

(°C

)

Date Fig. 5-4-3. Sediment temperature record at PWT-1 (ch1 is the deepest sensor and the ch7 is the shallowest).

6. Future Study 6-1. Biology

The microbial community structures of the sediments obtained from the front of the accretionaly prism at the Nankai Trough will be studied. Also, the correlations between the polychaete community and environmental conditions (oxygenated iron materials and swaying water) will be analyzed based on the microbial diversity study. (CK)

Unfortunately, the Abyssoanthus nankaiensis specimens from the Nankai Trough were inadvertently sampled, and there were only a few polyps available for examination. In situ observation is needed to further clarify some morphological features (tentacle count, etc.). Further examination of samples using electron microscopy and other techniques to analyze if A. nankaiensis is in symbiosis with chemosynthetic bacteria are also needed. Additionally, samples from different depths in the Nankai Trough need to be examined to see if these zoanthids are A. nankaiensis or another new species. We have also made arrangements with Shin-Enoshima Aquarium to attempt to rear and keep some Abyssoanthus samples alive in captivity, providing even more valuable ecological information on this enigmatic new family of animals. (JDR) 6-2. SSS/SBP M. Joshima, K. Kisimoto, K. Nishimura Sub-bottom structure around the ODP drilling site area using sub-bottom profiling equipment, StrataBox. M. Joshima, K. Kisimoto, K. Nishimura Reconstruction of ODP drill casing positions around the sites using forward looking sonar of KAIKO.