Continued: Jellyfish numbers swell by swarms and smacks

ORANGE BEACH, ALA.

This year, purple flags warning of dangerous marine life have flown at Alabama beaches more often than years past, signaling everything from the arrival of thousands of Portuguese men-of-war in April to more recent swarms of sea nettles and pale electric pink moon jellies.

"It seems to have been an exceptional year for them," said Orange Beach Coastal Resources director Phillip West. "I don't recall ever seeing as many and seeing them so early."

From Alaska to Africa, Australia to Alabama, scientists have noted that jellyfish populations are on the rise.

Monty Graham, a Dauphin Island Sea Lab researcher who specializes in jellyfish, said about 100 types of jellies are swimming in the Gulf of Mexico. That number includes many species that scientists, using genetic data, recognized only in the last decade, as well as invasive species new to the area, Graham said.

Scientists say the reasons are varied: rising ocean temperatures, increased nutrients and phytoplankton growth, overfishing of jellyfish predators as well as their finned competition on the food chain, depleted oxygen levels and the addition of man-made breeding grounds such as oil platforms, piers and reefs.

As a tickle in the throat can signal impending flu, some scientists warn, so might the apparent planet-wide increase in jellyfish spell looming sickness for the world's oceans.

From a May report by the National Science Foundation: "Scientists generally agree that human-caused stresses, including global warming and overfishing, are encouraging jellyfish surpluses in many tourist destinations and productive fisheries."

Long the bane of beachgoers, a sizzling welt is now low on the reasons to worry about jellyfish, scientists say.

"People should be more concerned about the ecological effects than being stung on the beach," Graham said.

On a recent day, Graham and a pair of his fellow Sea Lab researchers, Randi Shiplett and Mairi Miller, went in search of a smack of jellies 4 miles wide that a colleague spotted from a plane the day before.

About 2 miles south of Perdido Pass, they found a swarm. Though not as dramatic as some recent blooms, there were hundreds, if not thousands, of nebulous moon jellies and fluttering, milky sea nettles drifting by the small boat.

Graham, who sports a sea nettle tattooed on his right calf, and Miller, who has two jellies inked on her back, dove into the water with a video camera to document the aggregation. Meanwhile, Shiplett, a graduate student, collected jellies to take back to the lab so that she could dissect them later to see what they were eating.

A group of jellyfish is called a smack, and usually when jellyfish make the news, they appear in improbable numbers.

Last fall, a swarm that covered 10 square miles killed $2 million worth of salmon at a fish farm in Northern Ireland. In Japan, jellies have clogged coolant intakes at nuclear power plants. Meanwhile, Japanese scientists are experimenting with ways to use jellyfish, including extracting a compound from them that can be used to help cosmetics retain moisture and using them as a sort of biofuel to produce power.

In Alabama, jellyfish have prompted several headlines over the past decade. In April, hundreds of Portuguese men-of-war -- carnivorous creatures that administer a powerful sting -- washed up in Orange Beach. Basketball-sized Australian spotted jellies were so thick in 2000 that they basically shut down shrimping and choked inlets around Mobile.

That same fall, tens of thousands of 60-pound pink jellies -- Drymonera dalmatinum -- with 70-foot-long tentacles appeared in the Gulf.

Recently, Graham said, a Sea Lab trawler ran into masses of moon jellies south of Dauphin Island that were so thick researchers were unable to hoist the boat's net back to its deck.

Jellyfish are found beneath the Antarctic ice shelf, hugging thermal vents at the bottom of the Pacific Ocean, dominating tropical saltwater lakes, and, to the dismay of many vacationers, bobbing in the surf along beaches from Fort Morgan to Monaco. They've even lived in Utah: Last fall, scientists found fossilized snapshots of jellies imprinted on rocks that were more than 500 million years old, a discovery that pushed back the first known occurrence of jellyfish 200 million years.

The ocean sunfish, Mola mola, eats jellies. So do spadefish and sea turtles, which a 1981 study found often ingest bits of plastic they mistake for jellies. People are also predators.

Jellyfish have been served in China for more than 1,700 years. More recently, they've become a culinary staple in Japan, where they come packaged with sauces and ready to eat.

Jellyfish themselves are not usually selective eaters. Most eat whatever's in the water, including phytoplankton, roe and small fish. The variety of the roles they can play in food chains is often underestimated, with some sitting at the top with sharks and others, feeding on microscopic organisms, residing near the bottom, Graham said.

Some, like the trash-can-lid-sized Drymonema dalmatinum, eat other jellyfish. The pink globs that arrived eight years ago in vast numbers dined voraciously on native moon jellies.

Jellyfish can also eat themselves.

Graham captured video of one Drymonema whose tentacles had swung up and begun to digest its own bell. Jellies also have the ability, when food is scarce, to shrink. They accomplish some of this by ingesting their own parts -- gonads and everything else that is not essential to their immediate survival -- and then growing them back when food is found, said the Sea Lab's Miller.

Shiplett said she suspects her thesis will show that jellyfish eat a lot of eggs of commercially important species such as snapper and red drum.

Because of their versatility, ubiquity and ability to thrive in damaged environments, jellyfish are often pegged as the "cockroaches of the sea." In an article published this year, Graham ponders that nickname.

"There is no doubt that jellyfish will continue to increase and make the most of better conditions and new niches in the food chain," he writes. "I also suspect cockroaches will be long gone when the last jellyfish swims in a lonely sea."