ORT DOUGLAS, Australia — When Robert King climbed
back on the boat after snorkeling off the Great Barrier Reef
here on March 31, he knew something was wrong. "I don't feel
so good," he said, rubbing his chest.
He had been stung by a jellyfish, and his condition
deteriorated rapidly. By the time the emergency helicopter
arrived, he was screaming in agony; a few hours later he was
in a coma, eyes frozen wide, bleeding into his brain. He never
Mr. King, 44, from Columbus, Ohio, was the second person in
Australia to die this year from the sting of a species of
jellyfish, Carukia barnesi, found only in Australia and never
before known to be fatal. More than 200 other victims went to
hospitals, several times the number in a normal summer season
In many places around the world, jellyfish populations are
sharply increasing, stinging more people and wreaking economic
damage. While in some areas the increase appears to be part of
a natural cycle (jellyfish populations are declining in some
other areas), scientists have noticed an overall upward trend.
And they suspect that human activity is to blame.
"Jellies are a pretty good group of animals to track
coastal ecosystems," said Dr. Monty Graham, a jellyfish
scientist at the University of South Alabama. "When you start
to see jellyfish numbers grow and grow, that usually indicates
a stressed system."
Those stresses include increased water temperature, a rise
in nutrients in the water and depleted stocks of other fish,
all of them often caused by humans.
Higher nutrient levels in the water, which tend to support
larger populations of jellyfish, can result from runoff of
fertilizer and sewage. Overfishing removes the jellyfish's
main competitor for food.
Debate continues about the rising water temperatures
worldwide and whether they result, at least partly, from
global warming — the greenhouse effect caused by the burning
of fossil fuel. Being mostly water, jellyfish react strongly
and quickly to all of these changes. In a sense, the jellyfish
is like the pigeon in today's cities, able to flourish in
environments distorted by humans while other species cannot
survive at all.
Distinctly unlike the pigeon, however, jellyfish release
millions of microscopic harpoons when touched, shooting tiny
hypodermic needles into a victim's skin. They are lined with
barbs and filled with venom, and they often linger painfully
in the skin for months after the toxin has worn off.
That experience is becoming more common around the world.
On Waikiki Beach in Hawaii, for example, a lifeguard, Landy
Blair, counted more than 900 stings on a single day this
season, about 1 percent of them sending victims to hospitals.
Mr. Blair has been keeping track of jellyfish populations near
the beach since 1991. The problem has grown steadily worse, he
said, adding, "We have seen the highest numbers ever over the
On the beaches near Auckland, New Zealand, half a dozen
sting victims have required hospitalization this year, Robert
Ferguson of Surf Life Saving New Zealand, a lifeguard group,
reported. "It's the first time I've ever heard of victims
needing hospital care," Mr. Ferguson said. "This is a new type
of jellyfish with stings that are much more severe, much
The situation is the same in Australia. "This year is
incredibly abnormal," said Dr. Jamie Seymour, a jellyfish
expert at James Cook University. He believes that strong,
unusual wind patterns help blow the jellyfish toward the
shore, where they flourish in unseasonably warm waters. Dr.
Seymour, who has analyzed the venom from each sting that
receives hospital treatment in the Barrier Reef region for
years, had never seen the type of venom that killed the two
tourists this year.
Dr. Seymour believes that the enormous increase of
jellyfish near the shore has brought rarer, more deadly
subspecies into contact with humans for the first time.
Booming jellyfish populations can also take a high economic
toll. In the Gulf of Mexico, shrimp fishermen are struggling
with a jellyfish boom that fills nets with slimy gelatin and
financial ledgers with millions of dollars in losses.
While populations appear to be down this year, Dr. Graham,
of South Alabama, sees a "statistically solid increase" in the
region over the longer term.
Jellyfish first gained major scientific attention in the
1980's, when a huge jellyfish bloom devastated the Black Sea,
an ecosystem already weakened by overfishing of anchovies.
Scientists believe that the jellyfish, an Atlantic native
named Mnemiopsis leidyi, hitched a ride on the bottom of a
ship and then rapidly multiplied, feeding on anchovy eggs and
the plankton that young fish rely on.
More recently in Hawaii, overfishing of stocks like ahi and
mahi-mahi — as well as a depletion of sea turtle populations,
another predator of the jellyfish — is partly responsible for
the jellyfish boom there, said Dr. Angel Yanagihara, who heads
a jellyfish research laboratory at the University of Hawaii.
For her, jellyfish blooms are simply responses to the stresses
that humans have put on the environment. "It's a wake-up call
by nature," Dr. Yanagihara said.
Australia was stunned into action by the two deaths, which
officials fear could hurt tourism. "No one cared until someone
died," said Dr. Seymour, a member of a hastily convened
At the same time, some here see the jellyfish boom as an
opportunity. The Queensland Fisheries Service, intrigued that
Australian waters are so hospitable to jellyfish, is
considering setting up a commercial fishing operation for the
edible jellyfish Catostylus mosaicus. That fish is popular in
many Asian countries, but it is declining in Asian waters,
probably because of pollution.
Dr. Seymour said people could eat the highly venomous box
jellyfish if they cut the tentacles off, although he remains
fairly unimpressed with jellyfish as a food source. "They
basically taste like whatever sauce they've got on them," he