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A Whales footprint, left after surfacing by Humpback Whales (Megaptera novaeangliae) feeding on Krill in Wilhelmena Bay, Antarctic Peninsular. The whales migrate here in the summer to feed on the Krill. Krill numbers have declined by over 50%. They feed on algae that grows on the underside of sea ice, As the sea ice melts, both algae and krill decline. (KEYSTONE/SCIENCE PHOTO LIBRARY/ASHLEY COOPER/SCIENCE PHOTO LIBRARY)