To be precise, this is my 12th Sunday on Polarstern. As I participated in the transit from Bremerhaven to Cape Town, I have been on Board as long as the crew. Of course, my longing for my family, friend and home is growing, but Polarstern is an easy place to call home for a while. Even after all these weeks no feeling of everyday life has crept in. Each day is different from the previous, some are more exciting than others, but it is never boring.
On today’s program was, like on every Sunday, the weightwatcher’s club – one of the few regularly occurring events on board besides the meals. After that I went for the regular cooling container check-up. As we stopped station work a few days ago, I am glad to be able to keep some animals alive for experiments. I am one of the scientists here on board who work with zooplankton, i.e., with organisms of a few millimetres to centimetres in length living suspended in the water column. My special interests are amphipods and arrow worms (chaetognaths) from depths to 3,000 m. Arrow worms are not really worms, their name probably refers to their shape, but it may also indicate that their flight reaction is as fast as an arrow. Their position in the phylogenetic tree is still not resolved.
During this expedition I mainly investigate distribution and species composition of chaetognaths, but I also try to learn by experiments what they feed on. The aim is to find out about their life cycles and to get a better understanding of their position in the food web. This is a very interesting question because arrow worms, like many amphipods, are carnivorous, i.e., they feed on other zooplankters. Aside from abundance measurements, identifications and experiments, animals are also analysed with regard to their gut contents. They are frozen on board.
Samples are taken with the multinet which consists of five nets with a 100-µm mesh. It is employed for vertical catches and can take samples at five different water depths. To catch amphipods which typically can avoid the multinet, a multi-RMT (Rectangular Midwater Trawl) is employed as well. It consists of two frames of different sizes (1 m² and 8 m², respectively) and three nets each (0.33 mm mesh and 4.5 mm mesh, respectively). Contrary to the multinet, the multi-RMT is towed, samples a far larger volume of water and brings back a variety of bizarre zooplankton. Unfortunately, these large nets could only be employed once at greater water depths. We can only hope that we will fulfill our mission as an icebreaker for the Naja Arctica soon so we can resume station work. Until then, I continue to work with my animals and experiments, analyse data and enjoy the time in my current home, the Polarstern. Svenja Kruse, Alfred WegenerInstitute
Photo: S. Kruse and B. Ebbe, Senckenberg
Margot Foster is a journalist currently on board the Australian Aurora Australis, an Australian research vessel currently participating in the Census of Antarctic Marine Life (CAML, IPY project 53). She works with the Australian Broadcasting Corporation (ABC).
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Sunday, 13 January 2008 12:35
Another sunday on Polarstern...Written by Polarstern Expedition
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