Scientists working for the Australian Antarctic Division say the effects of climate change on the sea ice in which the krill that feed whales are bred can no longer be ignored.

Stephen Nicol, Anthony Worby and Rebecca Leaper warned in a paper published yesterday in the journal Marine and Freshwater Research, ''It is a matter of urgency that long-term studies are initiated to examine variability and change at all trophic levels in the Southern Ocean ecosystem to reduce uncertainty and to improve predictive power.'' (''Trophic levels'' are those related to nutrition.)

Dr Worby said yesterday that less sea ice meant fewer krill and fewer krill could also mean fewer whales. The massive declines in Arctic sea ice had not been repeated around Antarctica but the Antarctic peninsula was one of the most rapidly warming areas on the globe.

''The concern is that, if we have a significant decline in the amount of sea ice around Antarctica, what does that mean for the krill habitat and what does that mean for whale populations?,'' he said.

The study was particularly concerned with the ecological effects of climate change on baleen whales and the reproduction of krill, which feed and breed under the sea ice and constitute a Southern Ocean staple for many forms of marine life.

The study says sea ice is projected to shrink in Arctic and Antarctic waters, according to all future emissions scenarios. . AAP