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Algae disaster ‘unlikely’ in Lake Manatee

Boats docked at Central Marine in Stuart, Fla., are surrounded by blue green algae, Wednesday, June 29, 2016.
Boats docked at Central Marine in Stuart, Fla., are surrounded by blue green algae, Wednesday, June 29, 2016. The Palm Beach Post via AP

There’s blue-green algae in Lake Manatee. Many species, in fact.

But don’t put away the floaties and flippers just yet.

Just because the algae exists in the lake doesn’t mean that a toxic algal bloom as severe as the one from Lake Okeechobee will congregate in Lake Manatee, says the Manatee County utilities department.

On Jan. 30, the Army Corps of Engineers dumped toxic water from Lake Okeechobee into the St. Lucie Estuary to prevent flooding in the lake. The blue-green algae that came from Lake Okeechobee is now causing a toxic crisis to beaches in Martin, St. Lucie and Palm Beach counties.

A whole host of algae exists in Lake Manatee, said Manatee County water division manager Mark Simpson. The ones that are problematic to the lake are species of anabaena, a blue-green algae that produces a compound that releases a “musty, earthy smell.”

Even with algae in the water, it’s still safe to drink. Nearly three-fourths of Manatee County residents living in unincorporated portions of the county rely on the lake for drinking water.

“We don’t have issues with that and never had issues regarding individuals,” said Amy Pilson, public affairs liaison for the Manatee County utilities department.

On Friday, U.S. Rep. Vern Buchanan, R-Longboat Key, urged Congress to approve bipartisan legislation to help protect the state’s coastline from foul water discharges from Lake Okeechobee.

Buchanan, chair of the Florida congressional delegation, is a co-sponsor of legislation to require the Army Corps of Engineers to expedite repairs to the Herbert Hoover Dike and control water levels in the lake. The legislation would direct the federal government to complete repairs to the Herbert Hoover Dike, a 143-mile dike that encompasses Lake Okeechobee. The Herbert Hoover Dike has been rated as “critically near failure” by the Army Corps of Engineers.

“The algae bloom crisis has quickly become a public safety and health concern,” Buchanan said in a press release. “Florida’s waterways, coastline, economy and fragile ecosystems are at risk.”

Size matters

Lake Manatee was created after the dam was built in the mid-1960s. Simpson said the lake has been dealing with algal blooms of all kinds since its inception.

But there’s a key difference between Lake Manatee and Lake Okeechobee.

Lake Manatee is 3.75 square miles, whereas Lake Okeechobee is 730 square miles. The Manatee River basin is 360 square miles, but the basin of Kissimmee River, which feeds into Lake Okeechobee, is 2,940 square miles.

“The orders of magnitude are greater than what we have,” Simpson said.

Since the Kissimmee River basin is nearly 10 times the size of Manatee River’s, it far more likely to take in a greater amount of nutrients from sources like residential runoff and agricultural fertilizers.

For algae to grow, it needs a perfect combination of warm water, sunlight and three nutrients: carbon, phosphorus and nitrogen. Natural nutrients are always present, coming from rock in the earth or sediment lingering on the bottom. The algae issue is common in all surface water in Florida because of this presence of nutrients and Florida’s subtropical climate.

Blue-green algae has a competitive advantage to other algae because it can fix nitrogen from the air.

Simpson said the water from Lake Okeechobee was displacing water that had lower nutrient levels, which created opportunity for algae to grow so quickly.

Water from Lake Manatee is put into the Manatee River in small amounts daily as part of a permit or in order to prevent flooding.

“There’s never been a direct link between what’s in Lake Manatee and algae growth in the river,” he said, noting that there’s never been a warning issued at Lake Manatee regarding toxic algae concentrations.

What’s being done

The anabaena at Lake Manatee is believed to have the ability to produce toxins, Simpson said, but to date they’ve seen that the levels are low and infrequent.

“We’re always concerned and we’ll always be monitoring to be aware of what the issues are,” he said.

Preventive measures taken so that toxic algal blooms don’t happen at the lake include solar-powered circulators, which are always in the water preventing algae from staying in its ideal growing conditions, and algaecide, administered in high concentrations before blue-algae causes a problem.

The algaecide also affects “good” algae, like diatoms and green algae, but mainly destroys blue-green algae. But an algal bloom of any kind, toxic or not, will cause some degree of a problem, Simpson said, whether it’s depleting oxygen in the water or producing a rancid smell.

“We wouldn’t expect to see it here,” he said.

Hannah Morse: 941-745-7055, @mannahhorse

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