Each spring, Lyngbya bursts forth from spores on the seafloor and spreads in dark green-and-black dreadlocks. It flourishes for months before retreating into the muck. Scientists say it produces more than 100 toxins, probably as a defense mechanism.
At its peak in summer, the weed now covers as much as 30 square miles of Moreton Bay, an estuary roughly the size of San Francisco Bay. In one seven-week period, its expansion was measured at about 100 square meters a minute — a football field in an hour.
William Dennison, then director of the University of Queensland botany lab, couldn't believe it at first.
"We checked this 20 times. It was mind-boggling. It was like 'The Blob,' " Dennison said, recalling the 1950s horror movie about an alien life form that consumed everything in its path.
Suspecting that nutrients from partially treated sewage might be the culprit, another Queensland University scientist, Peter Bell, collected some wastewater and put it in a beaker with a pinch of Lyngbya. The weed bloomed happily.
As Brisbane and the surrounding area became the fastest growing region in Australia, millions of gallons of partially treated sewage gushed from 30 wastewater treatment plants into the bay and its tributary rivers.
Officials upgraded the sewage plants to remove nitrogen from the wastewater, but it did not stop the growth of the infernal weed.
Researchers began looking for other sources of Lyngbya's nutrients, and are now investigating whether iron and possibly phosphorous are being freed from soil as forests of eucalyptus and other native trees are cleared for farming and development.
"We know the human factor is responsible. We just have to figure out what it is," Dennison said.
Recently, Lyngbya has appeared up the coast from Moreton Bay, on the Great Barrier Reef, where helicopters bring tourists to a heart-shaped coral outcropping. When the helicopters depart, seabirds roost on the landing platform, fertilizing the reef with their droppings. Lyngbya now beards the surrounding corals.
"Lyngbya has lots of tricks," said scientist Judith O'Neil. "That's why it's been around for 3 billion years."
It can pull nitrogen out of the air and make its own fertilizer. It uses a different spectrum of sunlight than algae do, so it can thrive even in murky waters. Perhaps its most diabolical trick is its ability to feed on itself. When it dies and decays, it releases its own nitrogen and phosphorous into the water, spurring another generation of growth.
"Once it gets going, it's able to sustain itself," O'Neil said.
Ron Johnstone, a University of Queensland researcher, recently experienced Lyngbya's fire. He was studying whether iron and phosphorous in bay sediments contribute to the blooms, and he accidentally came in contact with bits of the weed. He broke out in rashes and boils, and needed a cortisone shot to ease the inflammation.
"It covered my whole chest and neck," he said. "We've just ordered complete containment suits so we can roll in it."
Fishermen say they cannot afford such pricey equipment. Nor would it be practical. For some, the only solution is to turn away from the sea.
Lifelong fisherman Mike Tanner, 50, stays off the water at least four months each year to avoid contact with the weed. It's an agreement he struck with his wife, who was appalled by his blisters and worried about the long-term health consequences.
"When he came home with rash all over his body," Sandra Tanner said, "I said, 'No, you are not going.' We didn't know what was happening to him."
Tanner, a burly, bearded man, is frustrated that he cannot help provide for his family. Gloves and other waterproof gear failed to protect him.