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SCIENCE

Icebergs releasing debris as they melt create
Icebergs releasing debris as they melt create "hot spots" of ocean life, a team of researchers reports. (By Nicolle Rager Fuller -- National Science Foundation)

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Monday, June 25, 2007

Sea Life Thrives Near Icebergs

Scientists have documented that global warming is causing the Antarctic ice sheet to shrink, with large chunks breaking off and forming free-floating icebergs in a trend that could portend substantial rises in global sea levels.

Now, a team of California-based researchers has discovered that those new islands of ice are breeding grounds for life in the Weddell Sea. As the icebergs melt, they release bits of rock, dirt and other debris, which enhance the growth of phytoplankton. Those microscopic plants attract krill -- small crustaceans that feed on them -- and the krill draw fish and fishing birds, and so on up the food chain, creating what the scientists call "hot spots" for ocean life.

"As global warming continues, you would expect to see more and more icebergs and hence more and more hot spots," said lead researcher Kenneth Smith of the Monterey Bay Aquarium Research Institute.

The phytoplankton also absorb the greenhouse gas carbon dioxide, so the hot spots probably need to be factored into global climate-change models to account for their role in removing carbon from the atmosphere, Smith said.

The researchers based their conclusions on data gathered around two icebergs in the southern Atlantic Ocean, including one that was 1,000 feet deep. They documented a "halo" effect of enhanced populations of phytoplankton, krill and other life as far as two miles from the icebergs. Their findings were published online last week in the journal Science.

-- Christopher Lee

Colo. Elk Lose Fear of Predators

Elk in Siberia that hear recorded calls of bears, tigers or wolves tend to cluster together, become vigilant and in many cases bolt in a near panic. Yet elk in Colorado's Rocky Mountain National Park that hear the recordings continue to graze with nonchalance.

A sign of American toughness?

Hardly. Rather, it is good scientific evidence that fear of predators is not hardwired into animals' brains but is maintained by ongoing exposure to the risk posed by those predators. The large carnivores that once attacked elk in Colorado have been gone for decades, and with those predators went the fear that once sent the elk fleeing.

Those findings, from research led by Joel Berger of the Wildlife Conservation Society in Teton Valley, Idaho, stand to help conservation biologists as they reintroduce predators such as wolves into areas where those animals have disappeared.


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© 2007 The Washington Post Company

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