Krill and the last ice

Southern Ocean +++ 60°’14’ S, 00°12’ E +++ -1 °C, open water +++
25 January 2015
(by Fokje Schaafsma)

In the last loose sea ice we got the opportunity to fish with the SUIT and the RMT once more. This was great because we haven’t been fishing under the sea ice a lot due to the lost time and our new route.

The many whales that had been spotted and the brown discoloration at the underside of the ice made us suspect that there might be a lot of krill in the area. Krill is an important food source for whales. Additionally, the brown color of the ice indicates that there are a lot of algae growing in it, which are an important food source for the krill. And indeed, after counting the catch of our first fishing attempt close to the ice edge, it turned out that we caught over 6,000 krill. More than enough samples to analyze, for instance, their stomach contents or to measure their energy value. But we will do this only once we get back home to our lab. Apart from krill, there were also a lot of amphipods in our nets, another crustacean species that we frequently encountered on this journey. The next fishing attempt close to the ice edge even exceeded the first one and yielded more than 11,000 krill.

During the sea ice stations we also collected ice cores. The cores were left to melt slowly in the ‘cold container’, our chilled working space. The work area is kept cool to ensure that the temperature difference between the samples and the outside temperature is not too big. After the cores had melted, we put the water through a fine mesh filter. Algae and other in-ice life remain on the filters, which we also will take home for further analysis. We spent many hours filtering in the container. The last ice core has been melted and processed and the cold container is now also ice free.

This week we fished with the SUIT in open waters for the last time and, sadly, it is time to start packing and prepare for the way home.

Impressions