Some are as large as washtubs. Scores have clogged boats' water intakes, stuck to propellers, and ripped fishing nets. In spots, they're so thick, one shrimper says, "You can almost walk on them."
They're Australian jellyfish, and it's hard to find anyone who's happy they're here. To shrimpers, they're a nuisance. To scientists, they're a sign of an unbalanced ecosystem. And to swimmers, they're just plain gross.
Apparently brought in on an abnormal eddy from the warmer climes of the Gulf of Mexico, the floating behemoths are already having an impact on the lives and livelihoods of people all along the Gulf coast. Dips in the ocean have been cancelled and fishing revenue has been lost.
Now, as the cooler winter season approaches, researchers are wondering how long the jellyfish will stick around, and what long-term impact they might have.
"These animals can actually take over an ecosystem and cause a collapse of commercial fisheries," said Harriet Perry, director of the Center for Fisheries Research and Development in Ocean Springs, Miss. "They [can] do some damage."
Scientists believe the jellyfish came through the Panama Canal on the hulls of ships in the late 1960s. The species has thrived in the Caribbean Sea since then, but this June, it made its first appearance in the northern Gulf.
And it has come in astounding numbers and grown to twice its normal size. A swimming race from Alabama to Florida had to be called off, and fishermen's boats and nets are being choked. "I got one in the [propeller], and the boat was shaking," says Percy Bradley of Long Beach, Miss., captain of the 42-foot Kar-Lyn-Dawn.
While the sting is only mild, the environmental and economic problems could be deadly. By consuming microscopic plankton, which are the foundation of the marine food chain, the jellyfish are a serious threat to the northern Gulf's ecology. Moreover, those plankton that are not being eaten are having trouble surviving in the new environment.
"[The jellyfish] make so much mucus that they make the water very viscous," says William Graham, senior marine scientist at Dauphin Island Sea Lab on the Alabama coast. "The small copepods are dying because there is so much gook in the water."
Elsewhere in the world, he notes, jellyfish have also been able to adapt in ways that could harm commercial fisheries. In the Black Sea, for instance, a jellyfish species proliferated as it consumed most of the food, eggs, and larvae of an anchovy fishery.
Scientists hope that increased rainfall or cold weather will kill or control the jellyfish. This summer's hot, dry conditions have raised salinity levels in the Gulf, helping them thrive. But Dr. Graham says something else is at work. On a research cruise, he found native jellyfish beyond their usual range and in higher numbers. He blames pollution.
Each summer, chemicals running into the Gulf from the Mississippi River feed algae blooms that deplete oxygen in the water, causing a "dead zone." This pollution situation allows jellyfish to proliferate.
"It happened to be a weakened ecosystem in the first place," adds Graham. "We've seen this around the world, where jellyfish started to dominate,... that's it."
(c) Copyright 2000. The Christian Science Publishing Society