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Water Quality Report: Blue-green algae is on the move

The Florida Department of Health in Lee County re-issued its warning that mildly toxic blue-green algae has built up to dangerous levels surrounding the David Boat Ramp.
Lee County Environmental Lab
The Florida Department of Health in Lee County re-issued its warning that mildly toxic blue-green algae has built up to dangerous levels surrounding the David Boat Ramp.


OLGA - The Sanibel-Captiva Conservation Foundation is one of the more active and impactful environmental grassroots groups in the region.

Among the many things the group does to help Southwest Florida’s marine environment, whether recovering from a hurricane or from mankind’s pollution, is to monitor the region’s water quality with a special focus on releases from Lake Okeechobee into the Caloosahatchee River.

Blue-green algae quite often first shows up at the Alva and Davis Boat ramps, which taken as a pair are way upstream and are the nearest large public boat ramps to Moore Haven where the Big Lake’s water is released into the river.

More than a century ago, the Army Corps of Engineers linked the Caloosahatchee River to Lake Okeechobee by digging a canal through the river’s swampy headwaters west of the lake.

These days, that waterway is the most common one the Army Corps uses to release water from Lake Okeechobee when levels are high. Problem is, the lake water is hopelessly polluted with nitrogen and phosphorus that’s flowed into it from more than a century of fertilizer use by industrial-sized agriculture operations and people wanting the grass to grow around their homes.

In 2018, heavy releases of lake water into the river are believed responsible for a massive blue-green algae outbreak that fouled the greater Caloosahatchee River estuary all summer. That summer was also the first after a big Hurricane Irma churned up the lake bottom in 2017.

Also called cyanobacteria, blue-green algae has already bloomed in the lake this spring and things are shaping up for a repeat of 2018 in the river this summer after Hurricane Ian set in motion the same events as Irma.

On a weekly basis, the SCCF gives its Ph.D-level recommendation to the Army Corps on how much water, and when, should be released from Lake Okeechobee into the Caloosahatchee River. Or not.

This week, the group’s tone turned serious:

“Recommendation: Entering into the rainy season, Lake Okeechobee is at a concerningly high level and has already started to develop worrisome cyanobacterial blooms. This sets up a potential scenario where the Caloosahatchee will experience damaging high lake-discharge events in addition to watershed runoff, resulting not only in increased nutrient loading and decreased salinity, but the transportation of harmful algae” into the Caloosahatchee River.

The flow of lake water into the river at many hundreds of millions of gallons per day has been ongoing for months.

The staff at the SCCF know greater Lee County’s maritime problems and successes very well. So it is no surprise that at the same time, they were jotting their letter to the Army Corps cautioning about blue-green algae-laden waters being a cause for concern downriver, the Florida Department of Health re-issued for the second week its health advisory warning people and their animals to stay away from the Davis Boat Ramp.

“Blooms have the potential to produce toxins, and what triggers them to do so remains poorly understood,” the health department wrote. “Since bloom conditions can change at any time, it is important to exercise caution as if the bloom were toxic, even if toxin presence has not yet been confirmed.

“You should not drink, swim, wade, water ski, or engage in activities that may cause you to come in direct contact with waters where there is a visible bloom. Exercise caution when using personal watercraft or boating, to avoid stirring up or contacting the algae or the affected water. Wash your skin and clothing with soap and water if you have contact with algae or discolored or smelly water.”


The Florida Fish and Wildlife Conservation Commission reported that over the past week the red tide organism, Karenia brevis, was detected in 13 samples collected from Southwest Florida in extremely low concentrations in Sarasota, Charlotte, and Lee counties.

The Clinic for the Rehabilitation of Wildlife received two birds with toxic symptoms from red tide or blue-green algae during the last week of May.


Sampling for components of blue-green algae by the Lee County Environmental Lab reported the presence of visible specks at the Alva Boat Ramp with some light streaks, and upstream of the Franklin Locks with some wind-driven accumulation along the shore and lock. Other components were found in moderately abundant amounts at the Davis Boat Ramp as streaks and wind-driven accumulation along the seawall.

Early this week, satellite imagery from Lake Okeechobee showed moderate-to-high bloom potential in Fisheating Bay and along the eastern shoreline. Cloud cover prevented the determination of the algae in the area of the bloom in more recent days.

What is red tide?

Red tide is one type of harmful algal bloom caused by high concentrations of the toxic dinoflagellate K. brevis, which is a type of microscopic algae found in the Gulf of Mexico. Red tide typically forms naturally offshore, commonly in late summer or early fall, and is carried into coastal waters by winds and currents. Once inshore, these opportunistic organisms can use nearshore nutrient sources to fuel their growth. Blooms typically last into winter or spring, but in some cases, can endure for more than one year.

Is red tide harmful?

K. brevis produces potent neurotoxins (brevetoxins) that can be harmful to the health of both wildlife and people. Wind and wave action can break open K. brevis cells and release toxins into the air. This is why you should monitor conditions and stay away from beaches where red tide is in bloom. People in coastal areas can experience varying degrees of eye, nose and throat irritation during a red tide bloom. Some individuals with chronic respiratory conditions like asthma or chronic lung disease might experience more severe symptoms. Red tide toxins can also affect the central nervous system of fish and other marine life, which can lead to fish kills.

What causes red tide?

A red tide bloom develops naturally, but recent studies have discovered mankind's infusion of other nutrients into the mix can make the red tide last longer or get stronger. But biology (the organisms), chemistry (natural or man-made nutrients for growth) and physics (concentrating and transport mechanisms) interact to produce the algal bloom. No one factor causes the development of a red tide bloom.


The National Oceanic and Atmospheric Administration, which has a satellite pointed at Lake Okeechobee that can detect harmful algae blooms found large groups of blue-green algae in the east-center of the lake.

Strong winds from Category 3 Hurricane Irma in 2017 churned up nutrient pollution from the depths of Lake Okeechobee, which helped feed a blue-green algae outbreak that covered 95 percent of the lake’s surface during the summer of 2018.

The much stronger Category 4 Hurricane Ian last September churned up Lake Okeechobee even more, so fears are that this summer will bring a blue-green algae outbreak even worse than the devastating one in 2018.

What is blue-green algae?

Blue-green algae, also known as cyanobacteria, are a group of organisms that can live in freshwater, saltwater or brackish water. Large concentrations, called blooms, can change the water color to blue, green, brown, orange or red. Some cyanobacterial blooms can look like foam, scum, or mats on the surface of freshwater lakes and ponds. As algae in a cyanobacterial bloom die, the water may smell bad

Is blue-green algae harmful?

Different types of blue-green algal bloom species can look different and have different impacts. However, regardless of species, many types of blue-green algae can produce toxins that can make you or your pets sick if swallowed or possibly cause skin and eye irritation. The Florida department of Environmental Protection advises staying out of water where algae is visibly present as specks or mats or where water is discolored. Pets or livestock should not come into contact with algal bloom-impacted water or with algal bloom material or fish on the shoreline. If they do, wash the animals immediately.

What causes blue-green algae?

Blue-green algae blooms occur when the algae that are normally present grow in numbers more than normal. Within a few days, a bloom can cause clear water to become cloudy. Winds tend to push some floating blooms to the shore where they become more noticeable. Cyanobacterial blooms can form in warm, slow-moving waters that are rich in nutrients. Blooms can occur at any time, but most often occur in late summer or early fall.

If any major type of water quality alert is issued, you can find the details here in WGCU’s Water Quality Report.

Environmental reporting for WGCU is funded in part by VoLo Foundation, a non-profit with a mission to accelerate change and global impact by supporting science-based climate solutions, enhancing education, and improving health. 

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