JR157: Seabed biology of Marguerite Bay, Antarctica


Cruise Diary

Date: Satruday 20 January 2007
Position: 67o34’S, 68o08’W Rothera Base, Antarctica

Chris writes:

"We have just slipped our moorings at Rothera and are heading back out into Marguerite Bay to start our science programme. However, our first task will be to attempt to retrieve a ‘lost’ mooring from a previous science cruise, a job for which Isis has already demonstrated a unique capability.

As we start the real science programme I thought it would be a good time to tell you more about the different equipment that the scientists will be using on this cruise, starting, of course, with the Isis.

Isis ROV – this cruise is a notable event in that this is the first time that the Isis ROV is being used for science and, as such, this trip has been the focus of some media attention. The Isis, which is funded by the UK government through the Natural Environment Research Council (NERC), is a National Marine Facility that is available for use by the UK scientific community. The ROV, which weighs in at about 3 tonnes, has a maximum depth capability of 6500m. It is powered through the water by six, 3.7 kW, thrusters and is attached to the ship for power and data supply via a 10000 m cable. The ROV is fitted with a number of cameras including a 3-chip, TV broadcast quality, camera with a 14x zoom, a 3.34 megapixel CCD still camera, a low-light CCD monochrome and a fixed wide-angle colour camera. The ROV also has a swath bathymetry system so it can map the sea floor at high resolution and a sonar system to detect any nearby obstructions. The two Kraft Predator manipulators on the front of the ROV can be used to collect sediment samples using small core tubes or to collect biological specimens which can then be brought to the surface in baskets. The Isis ROV will be our main scientific tool during this cruise.

More details about the UK Deep Submergence Isis facility, including details of the Isis team, can be found at the following site: http://www.noc.soton.ac.uk/OED/ROV/index.php.

Gravity core - This device consists of a 3m core tube on top of which is attached a heavy streamlined weight. It is attached to the ship via a winch cable and is positioned over the side using a ‘core bomb bucket’. Once in position a release on the bomb bucket is fired and the corer is allowed to free-fall to the sea bed. On impact the heavy weight drives the core tube into the sea bed to recover a sample which, depending on the sediment type, might fill the full length of the core barrel. These long core samples give a vertical profile through the sediment which is of use to geologists.

Box corer - This is a larger coring device but does not penetrate the seabed to as great a depth as the gravity core. It is lowered to the sea floor on a winch cable. A sample is then recovered from the sea floor as the core bucket is slowly driven into the seabed and closed off. These samples of known area and volume are extremely useful to biologists as they allow us to quantify the abundance of the different species of animals which live both on and in the sediment.

Most of the science will be carried out using Isis and the other equipment will be used to take particular samples in areas of interest.

Isis awaiting her first launch for a buoyancy test in Ryder Bay

Isis in the Antarctic

Gravity core showing weights in foreground
and core tubes racked in the background

Core bomb bucket with corer in stowed position
ready for deployment

Box corer

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January 2007
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