STUART, Fla. — A smelly, “guacamole-thick” muck is fouling a stretch of beaches promoted as Florida’s “Treasure Coast,” where lawmakers and residents blame the federal government, saying the algae crisis is fueled by freshwater flows controlled by Army officials to protect an erosion-prone dike.

The blue-green algae is the latest contaminant featured in yearslong arguments over water flowing from Lake Okeechobee, which is critical to South Florida’s water supply and flood control systems.

At Central Marine boat docks in Stuart, pea-green and brown algae coated the water Thursday and smelled like cow manure. Blooms that started last week in the St. Lucie River continue to spread, threatening Atlantic beaches expecting crowds for the holiday weekend.

Sarah Chaney, a receptionist at Central Marine, said boaters and fisherman are canceling reservations after seeing reports of the algae, which she called “horrible and disgusting.”

“I would describe them as guacamole-thick. And it stinks,” said Gabriella Ferrero, spokeswoman for Martin County.

Florida’s U.S. senators, Republican Marco Rubio and Democrat Bill Nelson, have joined Martin County commissioners in calling for the Army Corps of Engineers to stop the flow of water between the river and lake.

Residents and business owners blame the algae on pollutants streaming from the lake.

In a news release Thursday afternoon, the Corps said it would begin reducing the flow from the lake Friday.

After touring the St. Lucie River as it passes through downtown Stuart, Nelson said the problems can be traced to Florida’s history of diverting water to the ocean.

“We need to repair 75 years of diking and draining, but that takes time,” he said. He called on Florida’s Legislature to spend money approved by state voters for environmental projects, such as purchasing land around Lake Okeechobee for water storage instead of diverting the funds to pay for administrative costs. Rubio will visit the area Friday.

When Gov. Rick Scott declared a state emergency for the area Wednesday, he blamed the federal government for neglecting repairs to the lake’s aging dike that’s considered one of the country’s most at-risk for imminent failure.

Some residents blamed Scott instead. He hasn’t done enough to curb pollution from farms north of the lake or purchase land farther south where lake waters could be stored and cleaned, said Irene Gomes, owner of the Driftwood Motel in Jensen Beach.