It's going to be a long, stinky Fourth of July weekend on Jensen Beach.

Instead of red, white and blue, the color of the day is green. Thick, putrid layers of toxic blue-green algae are lapping at the sand, forcing Martin County officials to close the beach as a health hazard.

"I've seen Jensen Beach closed for sharks," said Irene Gomes, whose family has run the Driftwood Motel since 1958. "I've never seen it closed for an algae bloom before."

As bad as it looks, the stench is far worse, driving away Gomes' motel customers, chasing off paddleboard and kayak renters and forcing residents to stay indoors.

"It smells like death on a cracker," said Gomes' friend Cyndi Lenz, a nurse. Morgues don't smell as bad, she added.

The toxic algae bloom afflicting Jensen stretches for miles along the Martin County shoreline on the state's Atlantic coast near Palm Beach. It's also coating the water in the Indian River Lagoon and the St. Lucie River. It's thick in Lake Okeechobee, where the toxicity is 200 times what the World Health Organization says constitutes a human health hazard.

And now it's apparently showing up over on the state's west coast, too, forcing the closure of a popular park on the Caloosahatchee River and flopping onto Fort Myers Beach.

Gov. Rick Scott has declared a state of emergency and blamed the federal government. The state's U.S. senators, Bill Nelson and Marco Rubio, have stopped by for photo ops and expressions of concern. And national TV and radio news crews are broadcasting to the country a clear warning: Stay away from Florida right now.

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This economic and environmental disaster was cooked up in the stew pot that is Lake Okeechobee, where state officials have not required pollution limits to be met since those limits were created in 2001, according to Mark Perry, executive director of the Florida Oceanographic Society.

That's where the algae bloom started in May. Nobody knows what sparks an algae bloom, when a benign population of a few microscopic creatures suddenly explodes into millions, said Gil McRae, director of the Florida Fish and Wildlife Research Institute in St. Petersburg. Heat has something to do with it, and a good supply of nutrient pollution.

Lake Okeechobee is more than just Florida's biggest freshwater lake. It's also a repository for nutrient-polluted runoff from suburbs and farms around its rim and a reservoir for drinking water for communities south of the lake. The nutrients come from fertilizer, manure and septic waste.

The lake is also a threat, because the earthen Herbert Hoover Dike — built around its rim after a 1928 hurricane pushed it over its natural banks and killed hundreds — is at risk for leaking and collapsing. To reduce the chance of a breach during hurricane season, the Army Corps of Engineers tries to keep lake water levels between 12.5 feet and 15.5 feet above sea level.

Thus when heavy rains hit, as happened in January, the Corps starts dumping water from the lake. It goes west via the Caloosahatchee River into the waters surrounding Fort Myers and Sanibel, and east via the St. Lucie River into the waters around Stuart.

Inevitably, algae blooms follow, with seagrass die-offs, fishkills and other economy-damaging consequences. The last time there was a bloom close to this size and intensity, back in 2005, the estuaries took months to recover, Perry said.

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Scott contends the culprit is the federal government because it has yet to fix and raise the dike. But the affected coastal communities blame the state and the sugar industry. They have sought for years to get the water redirected south through what's now sugar land, but political opposition has proven too strong.

U.S. Sugar is among the largest donors to the governor's Let's Get to Work PAC, handing over another $100,000 in June. Rubio's campaigns have been fueled by sugar donations, too. After he announced his presidential run last year, he stepped off the stage and immediately hugged a sugar mogul.

In January, Scott signed into law a sweeping rewrite of the state's water policy that included a loosening of the restrictions on dumping pollution into the lake. Now, instead of going through a strict permitting process governing their discharges, sugar companies and other agriculture operations need only show that they're following a set of "best management practices."

"As long as agriculture implements those best management practices, they don't have to reduce their pollution discharges at all," said Ryan Smart, president of 1,000 Friends of Florida.

Sugar isn't the only powerful industry involved. Florida Agriculture Commissioner Adam Putnam recently proposed eliminating a rule requiring the fertilizer industry to submit monthly tonnage statistics on sales.

When the Times/Herald questioned the timing of that move, Putnam withdrew the proposed rule on Friday.

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When the lake began suffering from a 33-square-mile toxic blue-green algae bloom in mid May, the pulses of fresh water carried the toxic algae out into the coastal areas. The bloom was spotted May 13, Perry said, and within days it was growing in the St. Lucie estuary.

"Ever since May 14 we've been getting discharges with algae blooms," he said.

Normally the blue-green algae that thrives in fresh water is killed by encountering salt water, McRae said. But Perry said the heavy pulses from the lake — about a billion gallons of water a day — have provided enough fresh water to keep the algae bloom alive and growing.

He and Indian River keeper Marty Baum, who have monitored the health of that estuary for decades, both say this is the worst and largest algae bloom they've seen there. They noted the biggest risk is to human health.

"I'm … scared to death of that water," said Baum.

Residents say the bloom hit a tipping point about two weeks ago, becoming so big and thick that they couldn't avoid it no matter where they went. The stench grew so overpowering that at Central Marine in Stuart, the workers began wearing respirators just so they could keep breathing.

"The smell is 25,000 times worse than a sewer," said Central Marine's manager, Mary Radabaugh.

She handed out particle masks to anyone who asked until they ran out. Meanwhile, customers have been canceling appointments because they don't want to bring their boats through the green glop.

On Friday, Corps officials began cutting the flow of fresh water releases to about two-thirds the current level, in hopes that might alleviate the blooms.

"They really should be stopping it," said Gomes, the motel owner. "Give us a little breathing room."

Contact Craig Pittman at craig@tampabay.com. Follow @craigtimes.