Saturday 29th May 2010

We are still travelling towards our first sampling site in the north west target area of the cruise. The weather is getting worse, with increasing wind and sea state. Because of this, it was decided to do another test dive of the ROV. We particularly wanted to test the data acquisition and processing from the multibeam swath bathymetry system, and, of course, check that all the systems on the ROV were up-and-running. As we have a day of transit time left, this will give the ROV team a chance to make any adjustments and repairs.

 Before we got to the test dive site we all had the opportunity to test the enormous orange survival suits that will ensure that we remain warm if we were to have to leave the ship and board the liferafts. These suits are completely waterproof, with seals around the face, and have built in insulation. We took it in turns to try them on. The events were captured by our official photographer, who managed to somehow avoid having to do it himself…

Once we got to a suitable bit of abyssal plain (at around 3000m deep) we test dived the ROV. The ROV team skilfully manoeuvred the vehicle to do a 500m long swath bathymetry transect at 20m altitude (distance above the seabed). This revealed some fascinating pelagic organisms, such as jellyfish and ctenophores, that will be the subject of some of the research on the Mid Atlantic Ridge. The successful completion of the transect will give us bathymetry data that will enable a very detailed, centimetre-accurate, 3d map of the seafloor over a 40m wide swath to be produced. The ROV returned to the seafloor after this and began an extensive search for benthic, or seafloor, animals (there are no plants, as there is no light at these great depths). We found quite high numbers of echinoderms, with three members of this group represented: the sea cucumbers (holothurians), the sea stars (asteroids) and the brittle stars (ophiuroids). There were also quite numerous drop-stones – presumably dropped from past icebergs – that had a whole range of smaller attached animals (such as sponges and polychaete worms). The video picture on the ISIS ROV, being from a broadcast-quality high-definition camera, was superb and enabled the taxonomists to see the very small details of the animals that are required for identification. In some cases we will still need a specimen, to examine under the microscope or to look at internal structures, to permit accurate identification.

With the ROV retrieved we set off again towards the ridge. The weather is getting worse, so everyone has stocked up on curry and chocolate cake ready to face the storm tomorrow…

Daniel Jones

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One Response to Saturday 29th May 2010

  1. Rex Passion says:

    It is very exciting to be able to follow your researches. When I am in Cambridge I work at the Ichthyology Dept of Harvard. I am very interested in lanternfish (Myctophidae). They are covered with photophores, some of which seem to be covered with shutters, like a navy signalman’s searchlight. One can identify many myctophids by the patterns of their photophores, so any photos of these small fish would be of great interest.

    Rex

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