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Green Algae In Lake Okeechobee Thrives In High Temperatures

Gov. Rick Scott issued a state of emergency for seven counties around Lake Okeechobee, including Martin County where algae blooms can be found along the St. Lucie River including Shepard Park, shown here.
The Florida Channel
Leon County Judge John Cooper on June 30, 2022, in a screen grab from The Florida Channel.

Last week, Gov. Rick Scott ordered a state of emergency for seven counties around Lake Okeechobee as a result of toxic algae blooms. Now the Army Corps of Engineers is releasing water from the lake because the algae has spread to both Florida coasts, hurting home values, tourism and local businesses. 

The Everglades Foundation is kicking off a campaign to include the Everglades Reservoir in this year’s federal Water Resources Development Act bill. The reservoir would be designed to move water away from Lake Okeechobee and reduce the spread of the discharge causing the toxic algae blooms.

Sundial talked to ecologist Steve Davis with the Everglades Foundation about the dangers of toxic algae. Davis said the blue green algae species thrives in "high nutrient conditions," where high levels of nitrogen and phosphorus are present. In South Florida phosphorus is derived largely from fertilizers and thrives in warmer temperatures.

WLRN: [When] you talk about that phosphorus can we put a finger on who the culprit is?

Davis: No it's really an accumulation over several decades, contributions from north of Lake Okeechobee as well as a few decades of contributions from south of Lake Okeechobee and the Everglades Agricultural Area. It's led to a layer, several inches thick, of muck in the bottom of the lake that is very rich in phosphorus. We're also today still seeing high levels of phosphorus and nitrogen coming into Lake Okeechobee from the contributing basins to the north like Kissimmee River.

So all of that for decades has been piling up, sitting there at the bottom of the lake and eventually it gets stirred up and then it ... turns the water this really disgusting green that we've seen so many photos of now.

Yes. And we think that Hurricane Irma had a significant impact last year in September as the storm passed over the central part of the state and really whipped up the lake.

What's the risk to the wildlife but also to humans?

First we know that when algal blooms occur they occur in such abundance that they affect light penetration into the water that other organisms need. When you get into estuaries you think of sea grasses and the important habitat that they provide to coastal fisheries. When you have algal blooms in places like the Caloosahatchee Estuary near Fort Myers, that blocks out the light for seagrass so seagrass dies. Habitat is affected. These algal blooms also not only produce oxygen like a plant does during the day but they're also consuming oxygen over the nighttime and when you have very hot water and intense algal blooms we run into situations of hypoxic conditions over the nighttime hours. You'll have some species of fish succumbing to the very low levels of oxygen in the water that they need in order to survive but then we also add in this other layer that these organisms can produce toxins when they're growing in certain numbers and densities. It's the toxins that also become a compounding factor that result in human health concerns.

As with climate change the temperatures just keep going up. So is this just going to get worse?

We don't know. We can expect to see blooms like this in the future especially with warmer temperatures. We're learning that this particular species of blue green algae thrives in high temperatures. So as water temperatures get up to 95 degrees you might find that other algae reduce their uptake of nutrients and reduce their growth. This particular species seems to continue to thrive under those higher temperatures so we need to resolve the nutrient problem. But we've also got to find another outlet for that water and that's where Everglades Restoration comes in.

Copyright 2020 WLRN 91.3 FM. To see more, visit WLRN 91.3 FM.

Alejandra Martinez is the associate producer for WLRN&rsquo's Sundial. Her love for radio started at her mother’s beauty shop where she noticed that stories are all around her - important stories to tell.