August 3, 2008
Stinging Tentacles Offer Hint of Oceans' Decline
By ELISABETH ROSENTHAL
BARCELONA, Spain - Blue patrol boats crisscross the swimming areas
of beaches here with their huge nets skimming the water's surface.
The yellow flags that urge caution and the red flags that prohibit
swimming because of risky currents are sometimes topped now with blue
ones warning of a new danger: swarms of jellyfish.
In a period of hours during a day a couple of weeks ago, 300 people on
Barcelona's bustling beaches were treated for stings, and 11 were
taken to hospitals.
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 say. The
faceless marauders are stinging children blithely bathing on summer
vacations, forcing beaches to close and clogging fishing nets.
But while jellyfish invasions are a nuisance to tourists and a
hardship to fishermen, for scientists they are a source of more
profound alarm, a signal of the declining health of the world's
"These jellyfish near shore are a message the sea is sending us
saying, 'Look how badly you are treating me,' " said Dr.
Josep-María Gili, a leading jellyfish expert, who has studied them
at the Institute of Marine Sciences of the Spanish National Research
Council in Barcelona for more than 20 years.
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
These problems are pronounced in the Mediterranean, a sea bounded by
more than a dozen countries that rely on it for business and pleasure.
Left unchecked in the Mediterranean and elsewhere, these problems
could make the swarms of jellyfish menacing coastlines a grim vision
of seas to come.
"The problem on the beach is a social problem," said Dr. Gili, who
talks with admiration of the "beauty" of the globular jellyfish.
"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
Jellyfish, relatives of the sea anemone and coral that for the most
part are relatively harmless, in fact 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
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.
While no good global database exists on jellyfish populations, the
increasing reports from around the world have convinced scientists
that the trend is real, serious and climate-related, although they
caution that jellyfish populations in any one place undergo
"Human-caused stresses, including global warming and overfishing,
are encouraging jellyfish surpluses in many tourist destinations and
productive fisheries," according to the National Science Foundation,
which is issuing a report on the phenomenon this fall and lists as
problem areas Australia, the Gulf of Mexico, Hawaii, the Black Sea,
Namibia, Britain, the Mediterranean, the Sea of Japan and the Yangtze
In Barcelona, one of Spain's most vibrant tourist destinations, city
officials and the Catalan Water Agency have started fighting back,
trying desperately to ensure that it is safe for swimmers to go back
in the water.
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, said Xavier Duran of the water
agency. The constant squeal of Dr. Gili's cellphone reflected his de
facto role as Spain's jellyfish control and command center. Calls
came from all over.
Officials in Santander and the Basque country were concerned about
frequent sightings this year on the Atlantic coast of the Portuguese
man-of-war, a sometimes lethal warm-water species not previously seen
regularly in those regions.
Farther south, a fishing boat from the Murcia region called to report
an off-shore swarm of Pelagia noctiluca - an iridescent purplish
jellyfish that issues a nasty sting - more than a mile long. A chef,
presumably trying to find some advantage in the declining oceans,
wanted to know if the local species were safe to eat if cooked. Much
is unknown about the jellyfish, and Dr. Gili was unsure.
In previous decades there were jellyfish problems for only a couple of
days every few years; now the threat of jellyfish is a daily headache
for local officials and is featured on the evening news. "In the
past few years the dynamic has changed completely - the temperature
is a little warmer," Dr. Gili said.
Though the stuff of horror B- movies, jellyfish are hardly aggressors.
They float haplessly with the currents. They discharge their venom
automatically when they bump into something warm - a human body, for
example - from poison-containing stingers on mantles, arms or long,
threadlike tendrils, which can grow to be yards long.
Some, like the Portuguese man-of-war or the giant box jellyfish, can
be deadly on contact. Pelagia noctiluca, common in the Mediterranean,
delivers a painful sting producing a wound that lasts weeks, months or
years, depending on the person and the amount of contact.
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 or epicurean 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, according to Dr. Jennifer Purcell, a
jellyfish expert at the Shannon Point Marine Center of Western
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," Dr. Gili said.
Then there is pollution, which 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.
Residents in Barcelona have forged a prickly coexistence with their
Last month, Mirela Gómez, 8, ran out of the water crying with her
first jellyfish sting, clutching a leg that had suddenly become
painful and itchy. Her grandparents rushed her to a nearby Red Cross
stand. "I'm a little afraid to go back in the water," she said,
displaying a row of angry red welts on her shin.
Francisco Antonio Padrós, a 77-year-old fisherman, swore mightily as
he unloaded his catch one morning last weekend, pulling off dozens of
jellyfish clinging to his nets and tossing them onto a dock. Removing
a few shrimp, he said his nets were often "filled with more
jellyfish than fish."
By the end of the exercise his calloused hands were bright red and
swollen to twice their normal size. "Right now I can't tell if I
have hands or not - they hurt, they're numb, they itch," he
Dr. Santiago Nogué, head of the toxicology unit at the largest
hospital here, said that although 90 percent of stings healed in a
week or two, many people's still hurt and itched for months. He said
he was now seeing 20 patients a year whose symptoms did not respond to
any treatment at all, sometimes requiring surgery to remove the
The sea, however, has long been central to life in Barcelona, and
that is unlikely to change. Recently when the beaches were closed,
children on a breakwater collected jellyfish in a bucket. The next
day, Antonio López, a diver, emerged from the water. "There are
more every year - we saw hundreds offshore today," he said. "You
just have to learn how to handle the stings."