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Attack of the Jellies

It's like a scene from a bad '50s monster flick: Nation attacked by swarms of poisonous giant jellyfish! But that's exactly what's happening off the Japanese coast. The dishwasher-size Nomura's jellyfish, a gelatinous 400-pound blob with thousands of stinging tentacles, was once uncommon in Japanese waters. By early 2006, its numbers were estimated to be in the millions.

Elsewhere in the world, similar stories played out. In July, a creature called Mnemiopsis inundated Swedish seas; the invasive species is believed to have hitchhiked into the northern Atlantic by shipping vessel. And in September, millions of purple jellies called Pelagia noctiluca swarmed the Italian coast. The out-of-season visitors interrupted fishing operations and scared away beachgoers with their vicious stings.

From Tasmania to Namibia to the Gulf of Mexico, recent jellyfish invasions have puzzled scientists and devastated local economies. Closed beaches are the least of the problem.
Jellies have stung farmed salmon, clogged nets on fishing vessels, even blocked water-intake valves at nuclear power plants.

"The number of occurrences, their duration and geographical extent-all of those are exceptional," says University of Connecticut zoologist Ann Bucklin, who is heading up the count of zooplankton-marine animals that drift with currents-for the Census of Marine Life, an international effort to count all ocean animal species by 2010 (jellyfish are one type of zooplankton). "It appears to be outside the normal variation that we've seen in the past," she adds. "The [zooplankton] blooms seem to be dramatically more severe than they used to be."

Of all ocean species, jellyfish are among the least studied by scientists, in part because of their lack of obvious utility to humans, and in part because of the specific challenges of working with them. The invertebrates are difficult to handle, often poisonous, and prone to disintegrating when caught in nets. Our limited knowledge of normal jelly habits makes it tough for scientists to pinpoint what's behind the mysterious trend.

What they do know is that jellies are opportunistic animals that capitalize quickly on changing conditions. "The more food you give them, the more jellyfish you get," says marine biologist Jennifer Purcell, who has studied the connection between changing environmental conditions and jellyfish density. Warmer ocean temperatures, increased ocean acidity, agricultural pollution, and especially a decline in predators as the result of overfishing are all possible explanations for the recent jellyfish boom-and reasons why we're likely to see even more outbreaks this year and in the years to come.

Of course, some people are looking for ways to benefit. Japanese chefs have begun using jellyfish in more dishes and even cocktails, and researchers have harvested the animals' mucus for use in cosmetics. Call it the economy of a more gelatinous world.-Kalee Thompson

Turn the page to read about the dark side of the upcoming Olympics.