Seaweed blankets beaches in Qingdao, China

QINGDAO, China — As far as Li Lejun is concerned, there’s one easy way to make a July beach vacation even better than expected: Add seaweed. Hundreds upon hundreds of tons of it.

Buried up to his thighs in sand, his back covered in what looked like strands of chartreuse cotton candy, the 7-year-old Beijing boy was having the time of his life Sunday at No. 1 Bathing Beach in this city 350 miles north of Shanghai.

Ten paces to his right, men in swim briefs were using pitchforks to fling mounds of algae into a yellow front-end loader. In the other direction, a backhoe was scooping great piles of it into dump trucks. On Saturday, Lejun and his 69-year-old grandpa had helped gather globs of it from the sea, plopping it into plastic bags with other volunteers.

“It’s really fun to play with!” Lejun said. “It’s very soft and fun to touch.”

For at least the sixth year running, a giant algae bloom has engulfed the waters around this city like a bright green shag carpet mutating uncontrollably. This year’s seaweed mass has been measured at about 11,500 square miles — more than twice the area of Los Angeles County. Onshore winds help bring the strands ashore overnight, with some beaches buried under 16 inches of the floss-like flora, known to scientists as Ulva prolifera.

The seaweed began to appear a month ago, and officials have deployed 2,440 people, divided into 18 brigades, to try to keep pace with the annual phenomenon that turns Qingdao’s surf into something more resembling turf.

At No. 3 Bathing Beach, a supervisor surnamed Liu said Sunday that on the most severe days, he has 100 men who arrive by 3 a.m. to start clearing the water and the shore, using boats, nets and construction equipment.

“On a heavy day, we can load up 15 trucks; each load is 7 or 8 tons,” he said. “Sometimes we get 150 or even 160 tons in a day.”

The algae, known as hutai in Mandarin, flourishes in summer, when days are longer and the sun is high in the sky; growth can be kick-started by an abundance of nitrogen and other nutrients in the water.

Tim Nelson, a biology professor and seaweed expert at Seattle Pacific University, said those nutrients may either be naturally occurring — stirred up from deeper in the ocean — or brought by fertilizer washing into the sea from farms, golf courses and gardens. Once Ulva prolifera gets to proliferating, though, there’s little stopping it.

“How does it reproduce? How doesn’t it reproduce?” said Nelson, explaining that the algae can reproduce sexually or asexually — making spores and even fragmenting and regenerating itself. “It’s got a lot of flexibility.”

In general, the plant poses no danger to humans and intrepid beachgoers have been frolicking in the green seas, lounging on plushy-looking green beds of the material on shore, even burying themselves in big green haystacks of the stuff, which is helping Qingdao live up to its name, which means “Green Island.”

In 2008, the algae threatened to disrupt Qingdao’s hosting of the Olympic sailing competition, so the government dispatched 1,000 soldiers to help purge the waters.

These days, municipal authorities are carting off the seaweed to five processing depots, where the water is extracted and the material is dried, then processed into animal feed, fertilizer or a medicinal supplement known as hutai sugar, which is said to help lower blood sugar, according to a report in the Qingdao News.

Media coverage of the seaweed surge has caused a sensation in China, prompting netizens to brainstorm other uses for the mass of algae. One user of the microblog Weibo posted a recipe for a hutai dish that resembled guacamole. (Beer lovers, take note: The city’s eponymous Tsingtao brewery also produces a special green pilsner made with algae, though of the Spirulina, not Ulva, variety.)

In southern China, hutai is enjoyed as a food; dried, it sells for about $6 a pound. It can be fried with peanuts or shrimp, mixed into spring rolls, or made into pancakes with tofu, egg and flour.

Qingdao isn’t the only place that’s been inundated with such “green tides” — outbreaks have been logged in Puget Sound, Wash.; Rhode Island, England; and France.

It’s wise for Qingdao officials to clear the beaches daily because left unattended, the seaweed can rot and give off toxic hydrogen sulfide fumes, Nelson said. In 2009, a Frenchman riding his horse encountered mounds of the foul plant material along the Brittany coast; both man and beast were overcome by the gas, and the horse died.

Large algae blooms can also pose a hazard to sea plants and animals if the layer of growth becomes thick enough and dense enough to steal oxygen from patches of ocean, Nelson said.

Conditions for the algae growth are ideal, with water temperatures about 68 degrees. Once temperatures rise to about 73, the algae will sink or begin to die off naturally, Liu and others said.

Until then, Dong Jisheng, 61, will continue reporting for pitchfork duty at 4:30 a.m. at No. 1 Bathing Beach.

“There’s more this year than last year, it must have something to do with the changing climate,” he surmised. “It’s a natural disaster.”

Wu Chengyao, 38, a Chinese teacher visiting Qingdao from Anhui province, said he’s enjoying the hutai invasion while it lasts.

“I long for the sea,” he said Sunday, delighting in burying his bare feet into a soft mass of the seaweed along the shore, gentle waves lapping at his ankles. “This won’t discourage me at all.”

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Tommy Yang and Nicole Liu in The Times’ Beijing bureau contributed to this report.