Meteor Blog 17.-18. August: QUEST 226 - The final dive
The time had come for the final dive of underwater robot QUEST-what a success: If taking samples from the wood fall experiment, Videomosaicking or simply watching deep-sea organisms. Cruise leader Antje Boetius describes her impressions of the fascinating Deep Sea at the Westafrican continental margin.
Does the biodiversity of deep-sea organisms play a role for the climate on Planet Earth? Questions all about marine research will be answered directly aboard of the German research vessel Meteor by cruise leader Prof. Antje Boetius and her crew. In cooperation with the geoportal planeterde.de from 17.08.08 to 24.08.08 they contribute a Science-Blog of METEOR expedition M76/3 GUINECO – MARUM research of fluid and gas seeps on the Westafrican continental margin. Technical highlight of the cruise is the remote-controlled under water robot QUEST4000 by MARUM that will be deployed for taking fauna and sediments samples and conduction of in situ experiments. Go on a dive down to places no other human being has ever seen before: explore the fascinating deep-sea fauna and watch the scientists’ work at gas and fluid seeps deep down on the ocean bottom.
Expedition M76/3b is a collaboration of MARUM – Center for Marine Environmental Sciences at Bremen University and its associated institutes MPI and AWI as well as the French research institute IFREMER and the University of Paris.
More Informationen of the Meteor-Blog, an overview of all contributions to the blog and expedition M76/3B:
17.-18. August 2008 (Author: Antje Boetius)
BLOG of 17-18 August 2008, Author Chief Scientist Antje Boetius (Introduced herself on 25 July 2008)
QUEST 226 - The final dive
After dive 225 we were facing the same situation again: the ROV came up with a twisted cable (picture 1). But being so close to the end of the cruise, our ROV team collected again all their forces and used the 17 August for another repair phase, to permit a final dive.
Picture 1 -
The cable of ROV QUEST is twisted. Unfortunately such an incidence
is really dangerous for the ROV recovery, and as a
consequence the cable is cut and re-terminated.
On the 17th we completed some Parasound transects to the mud volcano area (see BLOG 02.08.2008), and were intrigued by indications of a gas flare above the pie-shaped mud volcano in an area, which we had not covered with our video-transect. Unfortunately, the remaining time was too short to plan further work at these mud volcano structures as well as at the other interesting geostructures around the so called Diapir area close to the submarine Congo canyon, as still a few geological samples were needed in the REGAB area, not to mention the hope for a final dive.
Picture 2 - The TRACS are colonization experiments offering different surface materials for larval settlement, such as wood, carbonate and plant material
All scientists got together in the afternoon of the 17 August to plan QUEST dive 226. We came up with a list of tasks easily filling 24 hours and requiring a lift operation. Of course this was a risk, because a failure during the final dive would have left our expensive equipment at the deep sea floor. But everybody agreed that we should use the chance of a long final dive before steaming home, and that chance should be on our side. The tasks for QUEST dive 226 included deployment of several profiling instruments, recovery of some experimental moorings, biological samples, water chemistry and the time-demanding “videomosaicking” in the areas where we had worked most. This is a special task for the ROV, where it has to fly at a constant altitude and velocity and known track over the seafloor to visually map organisms and habitats. Producing visual maps of benthic habitats is the only way of arriving at quantitative estimates for the areal coverage of visible structures – for example of the different bivalve species, the tubeworms, the carbonates. For this task, QUEST is equipped with a high quality camera looking downwards, to produce video footage and images, which can subsequently be put together like a “Mosaic”, using the positioning information. This sounds simple, but is really a complicated endeavor due to the difficulties of underwater positioning (also see BLOG 07 Aug).
Picture 3 -
Wood is a favored habitat in the deep sea, even if it
does not belong there. Many animals are specialized in colonizing
Summarizing dive 226, it was really a
success. Despite the persisting oil leak, we arrived at a 24 hours dive before
the reserve (also see BLOG of 3 August) and already accepted as new home to
many shrimps (picture 3), which normally prefer tubeworms and mussels as
Picture 4 - The microprofiler measures oxygen penetration in the sediment, here close to the wood log
We even observed a shrimp eating feces of Calyptogena clams, so these critters seem quite promiscuous in their associations. The microprofiler was deployed close to the wood (picture 4), as well as really close to a patch of vesicomyid clams, another risk taking, because the fine microsensors break easily on the shell of a clam (picture 5). Our Eddy system (also see BLOG of 26 July for explanation of in situ payloads) was placed close to and away from vesicomyid clams for community respiration measurements (picture 6). Also, we stopped in the center to watch the beautiful assemblage of organisms in the dense tubeworm forest (picture 7). A peculiar feature of this habitat is the attachment of mytilid bivalves to the tubes, as well as the dense colonization by hydroid polyps.
Picture 5 - Here the microprofiler measures oxygen and sulfide fluxes close to vesicomyid clams
Picture 6 -
The eddy system records total community respiration in
the vesicomyid habitat
These are just examples of the fascinating deep sea life, and dive 226 truly gave us a feeling of how things could have been hadn’t there be so many technical issues. Again, we were truly grateful to our ROV team who did not give up and realized this final dive of the GUINECO mission.
Picture 7 - Tubeworm bushes in central REGAB teaming with life