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Jellyfish numbers up all over the world
By MaltaMedia News
Aug 3, 2008 - 6:30:05 PM
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 From Spain to New York, to Australia, Japan and Hawaii, jellyfish are becoming more numerous and more widespread, and they are showing up in places where they have rarely been seen before, scientists told The New York Times on Sunday.
But while jellyfish invasions are a nuisance to tourists and a hardship to fishermen, for scientists they are a signal of the declining health of the world’s oceans. The explosion of jellyfish populations, scientists say, reflects a combination of severe overfishing of natural predators, like tuna, sharks and swordfish; rising sea temperatures caused in part by global warming; and pollution that has depleted oxygen levels in coastal shallows.
“The problem on the beach is a social problem,” said Dr. Gili, a jellyfish expert. “We need to take care of it for our tourism industry. But the big problem is not on the beach. It’s what’s happening in the seas.” Jellyfish are the cockroaches of the open waters, the ultimate maritime survivors who thrive in damaged environments, and that is what they are doing.
Within the past year, there have been beach closings because of jellyfish swarms on the Côte d’Azur in France, the Great Barrier Reef of Australia, and at Waikiki and Virginia Beach in the United States. In Australia, more than 30,000 people were treated for stings last year, double the number in 2005. The rare but deadly Irukandji jellyfish is expanding its range in Australia’s warming waters, marine scientists say.
In Barcelona, one of Spain’s most vibrant tourist destinations, city officials and the Catalan Water Agency have started fighting back. Each morning, with the help of Dr. Gili’s team, boats monitor offshore jellyfish swarms, winds and currents to see if beaches are threatened and if closings are needed. They also check if jellyfish collection in the waters near the beaches is needed. Nearly 100 boats stand ready to help in an emergency.
Officials were concerned about frequent sightings of the Portuguese man-of-war on the Atlantic coast, a sometimes lethal warm water species not previously seen regularly in those regions. Further south, a fishing boat from the Murcia region called to report an off-shore swarm of jellyfish more than a mile long.
In the Mediterranean, overfishing of both large and small fish has left jellyfish with little competition for plankton, their food, and fewer predators. Unlike in Asia, where some jellyfish are eaten by people, here they have no economic value. The warmer seas and drier climate caused by global warming work to the jellyfish’s advantage, since nearly all jellyfish breed better and faster in warmer waters.
Global warming has also reduced rainfall in temperate zones, researchers say, allowing the jellyfish to better approach the beaches. Rain runoff from land would normally slightly decrease the salinity of coastal waters, creating a natural barrier that keeps the jellies from the coast.
Furthermore, pollution reduces oxygen levels and visibility in coastal waters. While other fish die in or avoid waters with low oxygen levels, many jellyfish can thrive in them. And while most fish have to see to catch their food, jellyfish, which filter food passively from the water, can dine in total darkness, according to Dr. Purcell’s research.
Although 90 percent of stings healed in a week or two, many people’s still hurt and itched for months. A small number of patients have symptoms that do not respond to any treatment at all, sometimes requiring surgery to remove the affected area.
© Copyright 2008 by MaltaMedia.com
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