Picture above: Volker Siegel measuring the length of krill. (Photo: Kjartan Mæstad)
When I came to the Antarctic for the first time in the late 1970s, the intention of our research cruise was very straightforward. At that time many countries around the world had established 200 miles exclusive economic zones around their coasts and more were to follow. Some countries had lost their traditional fishing grounds, so the idea was to search for freely accessible areas where potential harvesting of marine resources was still possible. One of these areas was the Antarctic Ocean, which was not regulated and open to everyone. Antarctic was not a pristine area, there had been harvesting of seals and whales in that part of the world for a long time, but fish and krill stocks had not really been exploited.
Cold winters in Antarcica become fewer and further apart. (Photo: Volker Siegel)
Our scientific knowledge was at that time still very limited. We knew what species of fish and krill we could expect to find where, but we knew little about quantitative aspects of stock sizes and the various species’ life cycles. Therefore, we also had some very good scientific arguments to study the biology of many of these species. At that time the general idea was that the Antarctic Ocean is a very stable environment with very harsh conditions for any marine life: Deep oceans, long ice-covered winters, and cold summer, altogether an environment not very favorable to living organisms.
But this turned out to be a very human perspective. Life in Antarctica had over millions of years adapted to the harsh conditions. Fish and krill grow slowly not because of cold temperature in their environment. During shorter periods their growth rates can be just as high as species in temperate areas. However, the growth period during the summer season is so short that their yearly growth is smaller than in other areas. The organisms manage this by increasing the efficiency of their digestive enzymes and reducing their energy consumption, making better use of the resources.
The Antarctic ecosystem was not only thought to be very stable, but also believed to be relatively simple and thus easy to study: A short and direct food chain from phytoplankton to krill to the large baleen whales. Research results showed that this is seriously over-simplified. There are many more connections between the different players in the game, phytoplankton, zooplankton like krill, salps, copepods and higher predators like whales, different species of seals, penguins and flying birds like albatrosses, all showing different priorities in their food requirements. So scientists were soon faced with just as complicated a food-web as in other ecosystems around the globe. To complicate the picture even further, it was found that this dependencies of species changes with season. For instance, krill is not simply a filter-feeder of phytoplankton, it does this in swarms over the summer period. During late winter when food supply in the water column is almost absent, however, these animals give up their swarming behavior and disperse under the sea-ice where they start to feed on the ice-algae attached to the underside of the pack-ice. So they switch from a pelagic filtering planktonic to a surface grazing animal.
There are so many other details we had to learn over years of research to get a better understanding of the ecosystem. However, in my opinion one of the most important results was to realize that the system is not stable but is fluctuating over time. Years of high krill abundance are followed by poor years influencing also the dependent krill predators. After establishing a long-term data series for almost 30 years now, we also see some developments that are of great concern. There are strong indications that the krill population is decreasing. The reason is most certainly not related to the krill fishery that had established over the past decades – it is still very small compared to the biomass available – but there seem to be environmental changes driving this development. Antarctica is warming up in its northern parts, the preferred habitat of krill. When you have a chance to go ashore during research cruises and visit the same islands over several years, you immediately realize that small glaciers have disappeared leaving little rivers behind and that larger glaciers are retreating.
For the ocean, winters with strong ice-cover along the Antarctic Peninsula become less frequent, but krill are dependent on their winter ice habitat. Krill do not mind the cold water temperature as we believed 30 years ago, but they need their icy overwintering feeding grounds to survive.
Isfjell i drift bak G.O. Sars (Foto: Kjartan Mæstad)
The Antarctic Ocean is a huge area with a huge living resource. It is far too big to survey regularly by a single nation with a single vessel. A strong international effort to study at least parts of the ocean is needed. The Antarctic Ocean is far away from most developed countries. However, it affects our climate on the northern hemisphere, and is in return also influenced by the rest of the world. Currently, dramatic changes seem to be happening in the Antarctic environment, which will have serious consequences for the ecosystem. Research surveys are of great importance to understand the ecosystem and to learn more about species’ life-cycles. At the same time an international monitoring system with regular surveys needs to be improved to trace the potential changes and to develop predictions regarding how the stocks and the ecosystem may change. This will help administrators and managers to take necessary actions. During the last 30 years I have seen a dramatic change in the reason for going to Antarctica and studying the area. It started out with the search for new resources and it turned slowly into a monitoring and conservation (including rational use) approach. The Antarctic deserves the effort, it is still one of few areas with large living resources, but it is also one of the most beautiful landscapes on this planet.
PhD in marine and fisheries biology at University of Hamburg.