Cape Town - It was unbelievably cold on the ice – down to a mind-numbing, body-freezing, frostbite-inducing –56°C at times – so getting into the seawater that was “only” –2°C felt positively balmy by comparison.
Well, only in a manner of speaking, of course.
That was the recent experience of two marine scientists from the Department of Agriculture, Forestry and Fisheries during an international research cruise deep into Antarctic waters to investigate bio-ecological aspects of krill, the tiny crustacean that looks something like a shrimp, and that forms the basis of the food-chain in the vast Southern Ocean surrounding Antarctica.
The staple food of the great baleen whale species like southern rights, blue whales and humpbacks, krill probably constitute the largest total biomass (living weight) of any animal species on the plant, with stock estimates ranging anywhere between 60 and 155 million tons.
Professors Lutz Auerswald and Sven Kerwath were taking part in the nine-nation expedition ANT-XXIX-7, done under the auspices of the famous German research institution, the Alfred Wegener Institute, and specifically its Helmholtz Centre for Polar and Marine Research, using its polar research vessel RV Polarstern, which has ice-breaking capability.
The aim of the nine-week research cruise was to investigate the importance of winter sea ice coverage for the development of krill, Euphasia superba, and especially its larval stages, in the Southern Ocean. Part of their work involved diving under the ice during two dive camps of nine and 14 days duration, set up on sea ice floes in the one-year pack ice.
This chilly work was aimed at helping them achieve a better understanding of the importance of sea ice coverage for krill development in winter, explained Auerswald, who has worked with Antarctic krill specialist Professor Bettina Meyer and her research group at the Alfred Wegener Institute since 2004.
“And I introduced Sven Kerwath (to them) a while ago,” he added.
Kerwath said he was grateful that Minister Tina Joemat-Pettersson had given them permission to join the prestigious research expedition, “and to be able to apply my expertise in such an extreme and challenging environment”.
“Although it was mentally and physically demanding to be on the ice at –56 ºC and to dive under the ice at –2 ºC, it was also a great experience.”
The under-ice landscape was “bizarre, alien and almost psychedelic with amazing colours”, he said.
“The natural light penetrates through the ice and illuminates the upper part of the crystal-clear water. The visibility seems endless but then fades away into the dark abyss of the 5 000m water column underneath. It took some nerve to do this work, and everybody was feeling a bit apprehensive at first.”
Auerswald, co-author of the expedition’s final report to the Alfred Wegener Institute, said he was proud to have been given the opportunity to contribute to the success of what he described as “this challenging but exciting research expedition”.
Dive studies had involved sampling krill from under the sea ice, and had also provided information on behaviour, distribution patterns and abundance of krill under the ice, he explained.
The dive operations were supplemented by research on the physical and biological composition of the sea ice habitat, using an remotely operated vehicle.
“After weeks of hard work, the results were very satisfying,” he said.
The RV Polarstern had sailed from the bunker station Cabo Negro, near the Chilean “Antarctic gateway” city of Punta Arena on August 16, then headed east on a transect from Patagonia to South Georgia.
After calibrating the vessel’s fish eco-sounder in the shelter of the Sunset Fjord of South Georgia, the cruise followed a north-south transect towards the South Orkney Islands, and the first dive camp was set up on an ice floe of the pack ice south-east of the islands.
Nine days later the expedition moved east towards the South Sandwich Islands, where the second, two-week dive camp was established on a suitable, stable ice floe.
Then the researchers moved northwards al