JAGO dives

(K. Hissmann, J. Schauer, T. Klagge and science team)

The manned submersible „JAGO“ (Fig. 5.23), operated by IFM-GEOMAR in Kiel, was used during MSM 15/1 for in situ documentation of the habitat, oxygen monitoring along transects close to the sea floor, and for sampling near-bottom water and sediments with push cores. The

DESCRIPTION MODEL-MANUFACTURER RANGE RESOLUT. RESPONSE TIME CH4 sensor (1) K-METS – Franateci 0.01-10

µM

2 nM ~ 2 min CH4 sensor (2) HydroC – CONTROS 0.1-100

µM 10 nM ~2 min O2 sensor Optode 3830 – AANDERAA 0-500 µM <1 µM < 25 s TV camera + light Multi SeaCam 1060 – DEEPSEA POWER&LIGHT

CTD SBE-19plus 0-9 S/m

-5;35 °C 7000 dbar

0.00007 S/m 0.0001°C 0.002% f.s.

Turbidimeter Wet labs ECO-NTU, controlled by CTD 0.0024-5 m ^-1 Fig. 5.21

Chimneys of seep found at St. 367.

Fig. 5.20:

MEDUSA system.

Fig.5.22

Map of the six transects surveyed by MEDUSA.

submersible has a maximum operating depth of 400 m and is therefore an ideal tool for a working area like the Crimean Shelf. JAGO can accommodate two persons, the pilot and a scientist/observer. The highly manoeuvrable vehicle has two large acrylic dome ports, one at the front (diameter 70 cm) and one at the top (45 cm). It is electrically driven and moves autonomously within the reach of the navigation and communication systems on board the support vessel. JAGO is equipped with USBL underwater positioning system, fluxgate compass, vertical and horizontal sonar, underwater telephone, digital video (HDV) and digital still cameras, CTD and a manipulator arm for collecting and handling sampling devices.

The compact size of JAGO (3 x 2 x 2.5 m LWH) and its relatively small weight of 3 tons allow a launch and recovery from a wide variety of ships with sufficient crane capacity (min. 5 tons SWL). The submersible operates worldwide and is regularly used from on board the German research vessels among which R/V MARIA S. MERIAN is one of the most suitable for JAGO. The vessel is an extremely stable platform, has a large working deck, and possesses three deck cranes with sufficient lifting capacity and outreach for save handling. Very helpful for the submersible operation is the "follow target mode" in the vessel's dynamic positioning system. It enables the vessel to automatically follow a moving target.

During MSM 15/1 JAGO was launched and recovered with deck crane #3 at the starboard aft deck. Both crane operators (N. Bosselmann, N. Kreft) knew JAGO from previous cruises, were familiar with the handling procedure and therefore assured safe launching and recovery. A recently purchased work boat (6 m DSB inflatable with aluminium hull and 60 HP Yamaha outboard engine) was used to tow JAGO away from the ship's side after deployment and back under crane position for recovery. While submerged, JAGO was tracked by POSIDONIA 6000 (USBL underwater positioning system from IXSEA), part of the ship's equipment (including Mini-transponder MT 861S-HD-R mounted on JAGO). The position data (ship and sub) were integrated into MIMOSA navigational software to display and follow both JAGO and MERIAN tracks upon GIS based bathymetric map layers in real time. The ship automatically followed JAGO in "follow target" mode. Communication between JAGO and MERIAN were maintained by acoustic underwater telephone ORCATRON and the ET/RT8x1 transponder (IXSEA) that is permanently installed on an extendable pole inside the vessel's bow.

Oxygen concentrations were measured with an Aanderaa oxygen optode (AADI 3830 S/N848) that was attached to JAGO's bow, approximately 40 cm above its lower side. The optode was connected via RS232/USB serial adapter to a Laptop for continuous data display and logging inside the submersible. Measurements were taken during the entire dive, during de- and ascent and while flying close over the seafloor along transects of various lengths (see Tab. 5.3).

The habitat was continuously video-documented with a SONY HDV Camcorder HVR-V1E mounted in the centre of JAGO's large front viewport. After each dive, post-processing of the original HDV video footages provided digitized copies of the video material with overlaid UTC time code for evaluation by the science party. During each dive, video still images were captured by video-grabber from the running camera. These images were integrated into the ALAMER dive protocol (detailed dive protocols are available in the APPENDIX, Section A.1), which was used by the observer inside JAGO to log observations and activities. Near-bottom water samples were taken with a 5 L NISKIN bottle attached to the port bow of the submersible. Sediment, sediment in-fauna and microbial mats were collected with push cores of 255 mm inner length and 72 mm diameter, max. 6 per dive. The push cores were stored in the sampling basket at the

lower front of the submersible. The sampling site was marked with site markers. A CTD (SAIV A/S SD204 Norway) at the stern of the submersible continuously recorded depth, temperature, salinity and density during each dive.

Dive sites were selected based on the multibeam charts, which were produced during the cruise. During MSM 15/1, JAGO performed a total of 19 dives to bottom depths of 100 to 376 m, with usually two dives per day (Tab. 5.3). The total dive time was 45 hrs 25 min, the total distance travelled along the seafloor was 22 km. Eighteen different scientists and technicians participated in the dives. Most of them entered a human-occupied submersible for the first time and therefore gained an extraordinary personal experience. Most dives focussed on the hypoxic - anoxic transition zone (120-170 m depth) with measurements of the oxygen concentrations close to the bottom along long transects, push coring mainly of or in close vicinity to bacterial mats, and documentation of the sparsely benthic community. Dive 1110(5) was dedicated to the inspection of the four free falling instruments deployed at 150 to 153 m depth. JAGO detected all four instruments by horizontal sonar from a distance of about 150 m. Particularly the legs of the

"Chamber lander" were found to penetrate too deep into the soft sediment and had to be adjusted for the next deployment of the lander. Dive 1117(12) was an "underwater-rendezvous" at 101 m depth between JAGO and the remotely operated benthic crawler MOVE (MARUM) (Fig. 5.24).

JAGO documented in close communication with the vehicle control unit on board the MERIAN the in-situ measurements and movements of the moving lander system on the sea floor. Dive 1123(18) was a deeper dive for push coring in the permanently anoxic zone. The vertical distribution of the mega- and macro plankton within the water column above and below the chemocline was documented during Dive 1124(19), a free water dive and the last one of the cruise. During most of the dives, bottom currents were moderate. They helped to clear visibility after steering up sediment by settling on the soft bottom for sampling. At times, marine snow was found to be dense close to the sea floor.

Handling of the submersible from on board the MERIAN went extremely smooth thanks to the professional support from the entire ships crew on deck, bridge and work boat and due to mostly very calm sea conditions.

Fig. 5.24

JAGO and MERIAN.

Fig. 5.23

MOVE under water, documented by JAGO.

Table 5. 3 Short JAGO dive table (for a more detailed version see APPENDIX Section A.1).