Toxic future: Why Lake O algae blooms will return every single year

You know those massive algal blooms that cover much of Lake Okeechobee each spring and summer? The ones that threaten the St. Lucie River and Caloosahatchee River estuaries, and everyone who lives around or spends time on them, with toxins?

Well, get used to them. They’re going to keep coming back to Lake O for a while. Year after year.

Toxic summers on Lake Okeechobee are the new normal.

“Having algal blooms on Lake Okeechobee is going to be our life until we can figure out how to do something about them,” said Paul Gray, science coordinator for Audubon Florida’s Everglades Restoration Program, who’s been studying the lake’s ecosystem for 35 years.

Asked if Lake O’s algal blooms are getting — and will continue getting — more frequent, bigger and longer-lasting, Gray replied, “Yes, yes and yes.”

You’d think this stark reality would goad the Florida Legislature into action. But while some efforts were made this past legislative session, most of it was fairly weak sauce and certainly won’t solve the Lake O algae problem anytime soon.

The ingredients

Water in the lake covers about 730 square miles, about 467,000 acres. And two of the three conditions blue-green algae, aka cyanobacteria, needs to form massive blooms — warm water and lots of sunlight — occur naturally in South Florida every summer.

The third, lots of nutritious food in the form of phosphorus and nitrogen, doesn’t occur naturally but has occurred for over 50 years as nutrient runoff from fertilizers, mostly from farms and ranches in the lake’s 3,700-square-mile (2.4-million-acre) drainage basin.

It hasn’t always been this way. Accounts from the early 20th century talk of the lake water being clear. And whatever nutrients that accumulated in the lake were flushed out by hurricanes.

Dense blue-green algal mats clump up at the gates of Lake Okeechobee’s Port Mayaca on May 4, 2023, in Martin County.

But by the 1960s, people were complaining about water quality.

“Even in the 1970s, the phosphorus levels in the lake were about 40 parts per billion; and chances of algae blooms increasing is about 50 parts per billion,” said Gray.

Today, the phosphorus levels average from 100 to 200 parts per billion in the middle of the lake.

In 1987, after several massive algal blooms on the lake, the Florida Legislature approved the Surface Water Improvement and Management (SWIM) Act, the first of several laws, projects and programs designed to restore Florida’s impaired waterbodies, including:

  • The Lake Okeechobee Protection Act in 2000
  • The Northern Everglades and Estuaries Protection Program in 2007
  • The Florida Department of Environmental Protection’s Basin Management Action Plan for the lake in 2014

None of it worked.

To quote “A Phased Assessment of Restoration Alternatives to Achieve Phosphorus Water Quality Targets for Lake Okeechobee, Florida, USA” by scientists at the University of Florida Department of Agriculture and Biological Engineering: “Despite this long regulatory history, and with more than 30 years since the SWIM Act was passed by the Legislature, no reduction in (total phosphorus) loading to the lake has occurred since 1990.”

In fact, the amount of phosphorus in Lake O steadily increased from 208 tons in 1973 to 579 tons in 2003.

Phosphorus in the lake totaled 285 tons in Water Year 2022, which ran from May 1, 2021, to April 30, 2022 — 145 tons more than what’s thought of as safe for the lake, states the South Florida Water Management District’s 2023 Environmental Report (specifically, Chapter 8B: Lake Okeechobee Watershed Protection Plan Annual Progress Report).

As bad as that sounds, Water Year 2022 was a relatively good year for the lake, as all that phosphorus was still 45% lower than the 520 tons dumped into the lake in Water Year 2021, and it was lower than the 10-year average of 531 tons.

The reason: Water Year 2022 was particularly dry, and less rain means less fertilizer-laden water flowing off farms and pastures and into Lake O.

The good, the bad and the algae

That’s the current state and long-term future of Lake Okeechobee in a nutshell: Even the best years are bad, and the bad years are catastrophic.

The answer would seem to be curtailing the use of fertilizer with nitrogen and phosphorus north of the lake, right?

Oh, if it were only that easy.

(BTW: It’s not easy, as the failure of the state’s Basin Management Action Plans and “best management practices” used by farmers shows. See VoteWater’s Deep Dive: “Big Ag’s big pollution is a big problem for Florida”.)

“Even if farmers north of the lake stopped using fertilizer entirely today, there are enough latent nutrients in the Lake Okeechobee watershed to send 500 tons of phosphorus into the lake for 20 to 50 more years,” Gray said, citing a 2010 study commissioned by the South Florida Water Management District.

Gray noted that Buck Island Ranch north of Lake O hasn’t used fertilizer “in 30 to 40 years, but water coming off the ranch still has phosphorus levels around 300 parts per billion.”

To meet state nutrient level guidelines for Lake O, the concentration of phosphorus in that water ought to be 40 parts per billion.

But once the watershed north of the lake becomes saturated with nutrients, it’s hard to prevent problems downstream.

So, if stopping the use of fertilizer won’t stop the pollution in Lake O, is the situation hopeless?

Why bother when you’re damned if you do (fertilize) and damned if you don’t?

Stop digging!

“The technical answer is, ‘When you find yourself in a hole, stop digging!’ ” Gray said. “This will be hard enough to fix, but adding more (nutrients) while we are trying, just makes it that much further to get there.”

One proposal hold back nutrients is the North of Lake Okeechobee Storage Reservoir, which would be built just north of the lake and hold about 54.3 billion gallons of water before it reaches the lake. Plans for the project are being developed now with hopes it can be submitted for consideration by Congress in the Water Resources Development Act of 2024.

The project would help control the flow of water into the lake, but without substantial manmade marshes (known as stormwater treatment areas) attached to it, the water won’t be a lot cleaner when it goes into the lake

“To get the water clean, you’ve got to go upstream to the source of the pollution,” said Mark Perry, executive director and CEO of the Florida Oceanographic Society in Stuart. “We know the water is dirty when it comes off the farms and pastures north of the lake. Why don’t we go up there, work with the property owners to hold and clean the water in detention ponds before it’s sent to the lake?”

Researchers at the University of Florida agree, writing in a paper on stormwater management on citrus groves that detention ponds, which hold water temporarily until it’s clean enough to release, and retention ponds, which hold water permanently until it percolates into the ground or evaporates into the sky, “vary widely in their pollutant removal capabilities, but can effectively remove a number of contaminants with removal rates as high as 95% and 99% for some non-dissolved nutrients and pesticides, respectively.”

Plus, it would cost a lot less to clean water at the source rather than trying to clean it once it’s in the lake.

To complicate an already complicated problem, there also are enough nutrients already in the estimated 200 million cubic meters of muck and mud at the bottom of Lake O to keep the lake polluted indefinitely,

Remember how we said that, back in the days before Florida’s population boomed, hurricanes would clean nutrients out of the lake? Now hurricanes just make matters worse.

First, all the rainfall from the storms increases the flow of pollutants into the lake.

Second, the storms’ winds whip up waves on the massive lake and churn up the bottom, moving the accumulated phosphorus and nitrogen back into the water.

Can anything be done to get rid of the so-called “latent nutrients” in the bottom of Lake O?

One idea is to build a circular dike in the middle of the lake and pump the mud inside it.

“It sounds far-fetched, but it’s the most feasible solution I’ve heard so far,” Gray said. “But, yeah, it’s got lots of problems.”

There’s an obvious political solution: Strengthen Basin Management Action Plans, eliminate the “presumption of compliance” granted to farmers who adopt the state’s “Best Management Practices,” or BMPs; and test to ensure those BMPs are actually achieving the nutrient reductions the computer modeling attributes to them.

Florida’s elected officials have opted to go in a different direction, embracing “innovative technologies” as a means of combatting toxic algae. But few if any of these technologies have proven viable at the scale needed.

And ultimately they’re just another way for lawmakers to avoid the tough choices.

Cracking down on farm runoff by far the biggest source of pollution in Lake O might be politically difficult but it’s environmentally necessary if we’re going to prevent Lake O from becoming a perpetual toxic stew.

The worst thing that can be done: nothing.

“So far we’ve just been kicking the can down the road,” Perry said. “We know where the pollution is and we know where it’s coming from. Now’s the time to get to work and clean it up.”