Seen in Grönland

In the cradle of lakes

The rapid melting of the ice masses in Greenland creates thousands of new lakes. Ruben Sommaruga, head of the Institute of Ecology, has conducted an international expedition to investigate the origins of lakes and published his findings in Nature's ISME Journal.

In 2012 Ruben Sommaruga and colleagues from Denmark, Belgium and Germany travelled to Greenland, the small town of Ilulissat, from where the expedition started, packed with tons of material for on-site investigations. "With a helicopter we flew over the impressive landscape of Greenland to our research site. The lake landscape has changed completely in the last two years alone," says Ruben Sommaruga, who used at that time recent NASA satellite photos to compare with lakes which have been newly created or which have already disappeared. Compared with the Alpine landscape, the scientists can observe and investigate the massive formation of new lakes due to the rapid decline in ice masses. "The youngest lake, which we have researched in the course of investigations of the Faselfad lakes in the Verwall Valley, was about 50 years old. In Greenland, we have been able to take samples from much younger lakes, from four years old to 500 years old," says the ecologist who describes that the landscape in Greenland is extremely dynamic. Thus, Sommaruga and the team of scientists witnessed the rupture of an unstable moraine, as a result of which a lake became a river. "It was also not easy to find a suitable place for researching and staying overnight. It was important for us to be as close to the Greenland ice sheet as possible and yet not exposed to the dangers of cheerful nature," explains Sommaruga. Equipped with rifles for self-defense against polar bears and research equipment, the team spent three weeks in a "moon landscape" described by them, in which they investigated over a hundred lakes.

Tents for science, social life and sleeping. (Image: Ruben Sommaruga)

Lakes and communities emerge

A challenge for Sommaruga and his colleagues was to get an overview of the thousands of lakes and to determine their age. "Old satellites and aerial photographs provided us with information about lakes, which were newly created and which have existed for a long time, but we also saw ourselves faced with the task of defining which water bodies we could actually call lakes," said the ecologist. When the ice masses melt, water remains in depressions and only when land between the water body and ice is created do the experts speak of a lake. "In the course of our investigations, we have not only measured the chemical and physical conditions in the lakes, but we have also focused on analysing the composition of the food webs," explains Sommaruga, for whom it was particularly exciting to observe how communities are establishing themselves in a new lake and how they are changing in a short period of time. As soon as lakes lose contact with the the Greenland ice sheet and turbidity clears up , there are major structural changes in the lake communities. "With increasing age of the lakes, the terrestrial vegetation in the catchment also changes. The environment changes from a barren to a green landscape," says Sommaruga of his observations. Furthermore, the scientist was able to observe that fish have settled in older lakes, in contrast to the "new born" lakes. Which organisms find their home in a new lake depends on certain factors such as wind and bird migration that spread organisms between the lakes. "In Greenland in particular, it should not be forgotten that many different organisms, but above all microorganisms, already live in the ice and can enter the lake through the meltwaters. "Not all of them will be able to survive in the water," said the scientist, who also talks about the importance of geese in Greenland," geese can land in the water and thus help to spread organisms. The scientists still know little about the dynamics in the lakes, but a recent interest is on theatmospheric pollution which has been stored in the the glaciers and now are transported to lakes and streams as a result of ice/glacier melting. "Greenland was the ideal place for us to explore the cradle of lakes and explore how new communities establishe. Since the lakes originated at a very similar sea level, it is also possible to exclude the influence of the difference in elevation as we experience it in the Alps," emphasises Sommaruga. Ruben Sommaruga was accepted in November as Fellow of the Association for the Sciences of Limnology and Oceanography.

Helicopter transports tons of material. (Image: Ruben Sommaruga)

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