HEALTH

Are Lake Okeechobee algae blooms headed to the St. Lucie River? Experts' summer forecast

Tyler Treadway
Treasure Coast Newspapers

Like the return of summer rains — and in large part because of them — algae blooms are back in Lake Okeechobee.

So far, the blooms have been small, short-lived and either not toxic or very slightly toxic.

That could change over the course of the summer. But will it?

Let's look at what's going on in Lake O and what could be coming there and in the St. Lucie River down the road.

Where are the blooms?

The Florida Department of Environmental Protection has reported several blooms, including:

  • April 22: "Small bright green particulates" of several types of algae with no toxins at the Moore Haven Lock and Dam, which releases into the Caloosahatchee River.
  • April 23: A very small bloom with no toxins on the lake side of the Port Mayaca Lock and Dam, the site where Lake O water is discharged toward the St. Lucie River. Water wasn't being discharged at the time or since then.
  • May 7: A "fragmented" bloom in the southern lake near Pahokee contained minute amounts of the toxin microcystin.

A satellite image taken May 3 shows a light bloom in the northwestern part of the lake.

May 3, 2019, satellite image of Lake Okeechobee

That's bad news, right?

That's not necessarily bad news, said Zach Welch, lead scientist for lake and river ecosystems at the South Florida Water Management District.

"It could be that small blooms now eat up the nutrients in the lake so that there won't be big blooms later in the summer."

Are blooms natural?

There's always blue-green algae — aka cyanobacteria — in the lake, as it is in most bodies of fresh water. The question is whether conditions will be right for the algae to form massive blooms: long, hot days and plenty of fresh water laden with nutrients, particularly nitrogen and phosphorus from fertilizer runoff.

You can pretty much bet on the long, hot days. The "X" factor is how much rain there'll be this summer to wash nutrients into the lake.

Large blooms have become more frequent in recent years because of increased nutrient levels. That's "the new normal," said Mark Perry, executive director of the Florida Oceanographic Society in Stuart.

But so far this year, nutrient levels are lower than in the past couple of years, Welch said, because of a relatively dry winter and the lack of a big, wet tropical storm — like Hurricane Irma in 2017 — to wash those nutrients into the lake.

More: Record phosphorus flow into Lake O casts doubt on management  

How big could the bloom get?

Several experts don't expect a huge bloom this summer like the one that covered 90 percent of the lake last summer.

"Generally, the lower the lake gets in the winter and spring dry season, the less intense the blooms are in the summer wet season," said Paul Gray, an Audubon Florida scientist who's studied Lake O for a couple of decades. "So the theory is, there won't be a raging bloom this summer."

Lake Okeechobee on June 29, 2018 is mostly covered by a cyanobacteria bloom according to a satellite image from NOAA, derived from Copernicus Sentinel-3 data from EUMETSAT

This spring, the Army Corps of Engineers drew the lake down to an 11-foot elevation instead of the 12 feet, 6 inches the agency usually wants the lake to be at the beginning of the summer.

One reason was to help plants on the lake bottom get more light and grow. Over the past few years, 44,000 acres of those plants dwindled to about 5,000 acres because of perpetual deep water.

The plants are starting to come back, though; and the more they do, the better for keeping large blooms away, said Lawrence Glenn, the water district's coastal ecosystem administrator. "The plants will compete with the algae for nutrients in the water."

More: Lake O's lower level debated among stakeholders

Otto Herrera, of Royal Palm Beach, takes a closer look at the algae from shore at Lake Okeechobee on Friday, June 29, 2018, at Port Mayaca. Herrera, who said he has lived in Florida since he was 12 years old and had never seen the lake, was traveling from Bradenton with a friend who suggested the detour. "I'm surprised about the green stuff," Herrera said. "I was hoping to see a beautiful lake, but the green … it was kind of disappointing, you know." Discharges from the lake to the St. Lucie River were starting to be reduced Friday, with a complete stop for nine consecutive days then resuming in pulses indefinitely, according to the Army Corps of Engineers.

Will blooms infest St. Lucie River?

If there are major blooms in the lake and if the Army Corps of Engineers discharges algae-laden water to the river, yeah, we could have algae blooms.

Again, because of the Corps' draw-down this spring, Gray said, "there's a lot more freeboard in the lake, more room for it to take on water. Unless June and July really break loose with rain, there shouldn't be a discharge risk until August and September, the hurricane lottery months when anything can happen."

Recalling how Hurricane Irma raised Lake O 3 feet in September 2017, Glenn said, "It only takes one wet storm to wipe out all the good news you have in the lake."

More: Hurricane Irma raises Lake Okeechobee 3 feet

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