Omen? Scientists dismayed as millions of aquatic animals swarm Antarctica

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April 28, 2011 – ANTARCTICA – Scientists are dismayed by the record number of whales swarming Antarctica. The sightings, made in waters still largely ice-free deep into austral autumn, suggest the previously little-studied bays are important late-season foraging grounds for the endangered whales. But they also highlight how rapid climate change is affecting the region. The Duke University-led team tracked the super-aggregation of krill and whales during a six-week expedition to Wilhelmina Bay and surrounding waters in May 2009. They published their findings today (April 27) in the online science journal PLoS ONE. “Such an incredibly dense aggregation of whales and krill has never been seen before in this area at this time of year,” says Duke marine biologist Douglas Nowacek. Most studies have focused on whale foraging habitats located in waters farther offshore in austral summer. Nowacek and his colleagues observed 306 humpback whales – or about 5.1 whales per square kilometer, the highest density ever recorded – in Wilhelmina Bay. They measured the krill biomass at about 2 million tons. Small, floating fragments of brash ice covered less than 10 percent of the bay. The team returned in May 2010 and recorded similar numbers. Smaller but still higher-than-normal counts were also reported in neighboring Andvord Bay. Advancing winter sea ice used to cover much of the peninsula’s bays and fjords by May, protecting krill and forcing humpback whales to migrate elsewhere to find food, Nowacek says. But rapid climate change in the area over the last 50 years has significantly reduced the extent, and delayed the annual arrival, of the ice cover, says Nowacek, who is the Repass-Rodgers University Associate Professor of Conservation Technology. “The lack of sea ice is good news for the whales in the short term, providing them with all-you-can-eat feasts as the krill migrate vertically toward the bay’s surface each night. But it is bad news in the long term for both species, and for everything else in the Southern Ocean that depends on krill,” says Ari S. Friedlaender, co-principal investigator on the project and a research scientist at Duke. –
King Crabs: It’s like a scene out of a sci-fi movie — thousands, possibly millions, of king crabs are marching through icy, deep-sea waters and up the Antarctic slope. “They are coming from the deep, somewhere between 6,000 to 9,000 feet down,” said James McClintock, Ph.D., University of Alabama at Birmingham Endowed Professor of Polar and Marine Biology. Shell-crushing crabs haven’t been in Antarctica, Earth’s southernmost continent, for hundreds or thousands, if not millions, of years, McClintock said. “They have trouble regulating magnesium ions in their body fluids and get kind of drunk at low temperatures.” But something has changed, and these crustaceans are poised to move by the droves up the slope and onto the shelf that surrounds Antarctica. McClintock and other marine researchers interested in the continent are sounding alarms because the vulnerable ecosystem could be wiped out, he said. Antarctic clams, snails and brittle stars, because of adaptation to their environment, have soft shells and have never had to fight shell-crushing predators. “You can take an Antarctic clam and crush it with your hands,” McClintock said. They could be the main prey for these crabs, he said. McClintock’s colleague Sven Thatje, Ph.D., an evolutionary biologist at the University of Southampton in England, saw the first signs of the king crab invasion in 2007. He spotted a lone crab climbing up the slope. McClintock and Rich Aronson, Ph.D., a paleoecologist at Florida Institute of Technology, put together a proposal to launch the first systematic search for king crabs in Antarctica. With Sven as chief expedition scientist, the team headed back with two ships and a submarine earlier this year. McClintock and his fellow researchers are exploring causes for the invasion, which they believe is linked to human-induced climate warming. Around 40,000 tourists visit the area each year. “The whole ecosystem could change,” McClintock said. “And this is just one example of a species expanding its range into a new territory. There will certainly be more as the climate warms up.” –Science Daily


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