ANT XXIII/8, Weekly Report No. 9, January 28, 2007

Last Sunday and Monday were filled up with the whole daily working program. This time we were sampling the former Larsen A ice shelf area. We made excellent progress regarding the steaming to stations and subsequent station work and were blessed with good weather and ice conditions. Something surprising happened when the Polarstern was manoeuvring as close as possible to the coast to study the former grounding line of the ice shelf as well as the re-colonization of the only recently freed seafloor. At the sight of almost vertically rising rocky cliffs we assumed that it would look similar below the sea surface. Instead, there was muddy sediment with an overall interesting fauna. However, this single station is not very representative of the whole of the Larsen A area. On our quest to confirm the hypothesis of two different benthic systems, Larsen A and B, we were equipped with only a bathymetric chart and some good intuition.

We steamed from north to south to a place where cone-shaped mountain tops which are situated on the border between Larsen A and B hold a narrow band of the remaining ice shelf in place. Because of the free passage of water masses beneath the ice we were expecting to find the same homogenous soft-bottom fauna on one side as well as the other. Again, we were surprised to find hard substrate which was covered with characteristic Antarctic filter feeders - glass sponges - so ubiquitous elsewhere. These animals inhabited this area even before the ice shelf broke off. The presence of juvenile sponges was also very conspicuous. Maybe, we witnessed the development to dense concentrations of sponges like those found in the eastern Weddell Sea close to the Neumayer Station. Three weeks ago during a bottom trawl on the other side of the Peninsula we caught sponges in such high numbers and size which is almost unheard of in the eastern Weddell Sea. This truly was a scientifically successful end of our research work in the Larsen area. It has to be also mentioned that fellow scientists relying on soft sediment were seldom short of opportunities to push their sampling tubes into the mud to obtain samples. This was due to the fact that we could almost always locate nearby depressions where soft sediment was accumulating. However, these samples will be mainly processed in the home institutes and did not reveal immediate results compared to imaging methods or dredges.

At the end we sampled two more reference stations outside the Larsen area. By Wednesday everyone that was involved to the last minute in the “Census of Antarctic Marine Life” program experienced hectic times of cleaning, packing boxes and finishing reports. We can look back on a successful and thanks to great weather conditions very pleasant expedition. Regardless of the permanent friendly atmosphere onboard the Polarstern we are all looking forward to go back home, some of us via a trip to South America.

For the last time, the chief scientist sends his regards to the relatives of all participants and to all those that were following this expedition with great interest.

Yours Julian Gutt