In the past six weeks scientists aboard the research vessel “Polarstern“ have been searching for krill in the previously scarcely investigated Lazarev Sea. The expedition ended today in Cape Town. As a food source for whales, seals, penguins and seabirds, krill takes a key role within this ecosystem of the Antarctic. Very little is known about the distribution, biology, population dynamics and physiology of these shrimp-like crustaceans, either from this ocean region or about the time period between the Antarctic autumn and winter. The expedition was to gather information on the protection of krill populations before the increasing industrial use of krill products may impact krill stocks and, consequently, the Antarctic ecosystem.
The fourth leg of the "Polarstern" expedition ANTXXI/4 included 38 scientists from seven nations and 43 crew members, and was part of the international programme "Global Ocean Ecosystem Dynamics“ (GLOBEC). This programme, which is run in coordination with the AWI, addresses the relationships between marine animals floating freely in the water column (zooplankton) and the physical conditions of the ocean environment. The fundamental research of the expedition also represents a German contribution to the population protection programme of the "Commission for the Conservation of Antarctic Marine Living Resources" CCAMLR).
In April of 2004, the krill's spawning season was already over. The krill underwent a physiological transition from high metabolic summer activity to a reduced winter metabolism. Concentrations of the krill's biochemical and pharmaceutical compounds of interest are analysed at the Alfred Wegener Institute. A scientific echo-sounder recorded the large-scale distribution of krill and, for the first time, to a depth of 600 m. Krill aggregations were relatively small and most abundant in the far south in areas of growing sea ice, as well as in the far northern fringe region of the Weddell Sea. In the central Lazarev Sea, small numbers of krill consumers also indicated small krill populations during autumn. In contrast, abundance of krill larvae was high. This was especially surprising as krill larvae, unlike adults, continually need to take up food, which is increasingly difficult to find during autumn and winter. Using a new type of under-ice drag-net, scientist were able to confirm that krill accumulate under extensive fields of ice floes where the animals feed on algae within the ice. Furthermore, krill is able to find protection from predators in ice crevices. Whether there is genetic exchange between the krill population of the Lazarev Sea with the heavily fished ones of the Antarctic Peninsula, will have to be inferred from appropriate laboratory analyses of the participating institutions. In the ice-covered regions, numerous larvae of several fish species as well as tunicates (salps) characteristic of warmer northerly waters were found, apart from krill. It remains unclear, whether alterations of current patterns or even climatic changes are the causal factors.
On June 2, 2004, "Polarstern“ will return to Bremerhaven.
Bremerhaven, May 6, 2004
Scientists investigate Krill in the South-Polar Ocean
