By Hanna Scheuffele & Henrik Christiansen |
By the 10th of January the 51 scientists of cruise PS 96 are celebrating half time. Exactly five weeks after departure one of the main goals of the cruise appears within reach: a depot on Ronne ice shelf – so far south that we can only be reached by Iridium communication here. Hence, regular internet connection and e-mail volume have to be cut down to a minimum.
Time to take a look back. We reported of flying companions, of ice in all its variations, of adventurous scientists, that were left out on the ice, of ice physicists, that love to fly with the helicopters and of previously unknown species.
The last blog entry described two gears used to catch a variety of invertebrates: The Agassiz Trawl and the Bottom Trawl. These very same nets are intentionally catching fish as well. Our look back proves: everything here revolves around ice. Fish are no exception, for the most famous Antarctic fish are called – of course – icefish. Their gills are white, their hearts yellow, and their blood is transparent. They lack haemoglobin, the pigment responsible for the red blood colour of all other vertebrates on Earth. They thrive in waters of -1 to -2 ° C and possess specific proteins that protect them against freezing. Some perform extensive parental care, others have managed to be neutrally buoyant without having a swim bladder, new species are still discovered on a regular basis… We could go on and on.
On board, an international team takes care of the caught fish. We put some of them in a special aquarium container with everything inside to make them feel comfortable. Furthermore, weight, size, sex and other data are being recorded and an extensive sampling protocol is being carried out. To speak in biological terminology: we have experts for reproduction biology, ecophysiology and -toxicology, transcriptomics and population genomics on board. Moreover, we collect material for trophic analyses, otoliths, and morphometric studies.
In the end everything leads to one central question: Will Antarctic fishes, with all their special adaptations, be able to react to the current changes in their environment (e.g. rising temperature, acidification, pollution, fisheries…). And if so, how? These questions can only be answered with a lot of patience and work on board, as well as back at the home institutes.
Enough from the fish for today. Yet, a lot of topics remain untouched. What exactly are the oceanographers trying to tell us biologists about the unique characteristics of this area, since the start of the cruise? What is going on with the Ronne Depot? What is the “magic gear”? And what do the scientists do when they are not working? Unbaptized Antarctic scientists might also be better off having some anti-freeze in their blood…
We will keep you posted.
Until then best wishes from the ship,
Hanna Scheuffele, AWI & Uni Bremen und Henrik Christiansen, Uni Leuven