Biologists from the Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research (AWI) have for the first time shown that amphipods from the warmer Atlantic are now reproducing in Arctic waters to the west of Spitsbergen. This surprising discovery indicates a possible shift of the Arctic zooplankton community, scientists report in the journal Marine Ecology Progress Series. The primary victims of this "Atlantification" are likely to be marine birds, fish and whales. The reason is that the migrating amphipods measure around one centimetre, and so are smaller than the respective Arctic species; this makes them less nutritious prey.
Amphipods have a preference which made it easy for AWI biologists to recognise these changes. This is because the sea dwellers, which are classed as zooplankton, would appear to like hiding. "Their favourite hiding places apparently include our sediment traps which have been suspended for 13 years in HAUSGARTEN, the AWI long-term observatory in the Fram Strait. We had originally anchored our funnel-shaped traps at a depth of some 300 metres there in the West Spitsbergen Current in order to catch downward floating material such as algae or excrement from zooplankton. However, from the start we also found several amphipods in the traps. The sample containers are full to the brim, especially in summer months. We therefore believe that the animals are actively swimming into the traps", states AWI plankton specialist Dr. Eva-Maria Nthig.
The by-catch rapidly proved to be a valuable sample set, because over years changes were not only seen in the number of amphipods caught, but also in the species composition. "In the first four years our catches consisted exclusively of the Arctic and sub-Arctic individuals Themisto libellula and Themisto abyssorum. We found examples of the smaller species Themisto compressa, which is native to the Atlantic Ocean, in our sediment traps in July 2004 for th
|Contact: Sina Loeschke|
Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research