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Water Quality Report: How red tide can be here, but not be here. Wait. What?

Red tide is not normally this colorful, but researchers are discovering it can also be deadly when it does not discolor the water at all
Centers for Disease Control and Prevention
Red tide is not normally this colorful, but researchers are discovering it can also be deadly when it does not discolor the water at all


How is it true that the building blocks of red tide are present in the ocean in Southwest Florida, and seabirds at Sanibel Island’s Clinic for the Rehabilitation of Wildlife are dying from ingested red tide toxins, but regular testing has not detected the harmful algae at the island nor anywhere else around Florida?

It reminds me of the famous lair's paradox: “This sentence is false.” Think about it and it’ll mess with your head.

If the sentence is true, then it must be false as stated. However, if it is false, then it would be true. Wait. What?

The contradiction of logic has been the topic of countless philosophical debates for centuries.

I’ve got nothing for you on solving a sentence that is true and false at the same time.

But I can explain how red tide can be here, and not be here, simultaneously.

“It can seem counterintuitive that animals are experiencing symptoms when K. brevis cell counts read as ‘not present’ or at ‘background concentrations," Allie Pecenka, who works in policy matters at the Sanibel-Captive Conservation Foundation, a partner with the CROW hospital. "But multiple explanations for this exist.”

The explanation lies in the mechanics of the sneaky basic component of red tide, Karenia brevis, the vernacular use of “red tide” versus the scientific meaning, in biology, and seagulls.

First, red tide is caused by really high concentrations of K. brevis, which in everyday terminology is a "bloom." Very low concentrations of K. brevis, however, are endemic off Florida and pretty much everywhere else and don't count as harmful algae blooms. Technically, that means red tide is present but the testing for it either excludes it or recognizes it and discards the finding. Otherwise, "red tide" would be present every time scientists test.

And besides, low levels of K. brevis are not "red tide." They are "low levels of K. brevis."

Marine researchers declare a red tide bloom when the "harmful" part starts to become noticeable, such as that acrid stench in the air that can cause coughing, runny eyes, and even asthma outbreaks in those prone to them, as well as dead fish washing up on the shoreline, which has its own lovely smell after a few days in the sun.

(Technically, scientists can and often do rely on "cells per liter" of water to decide if a K. brevis is multiplying enough to graduate to "bloom" status, which is the boring scientific meaning I referred to above.)

The biology of larger animals allows the toxins associated with K. brevis to move up the food chain. Predators higher up ingest the tissues of small fish and invertebrates, like oysters and crabs, containing the toxin during the feeding process. The toxin can also settle on plants, where it can remain long after a red tide event has passed and be further ingested by marine life.

“The largest predators tend to hold the highest levels of toxins, which build up faster than they can be broken down," Pecenka said. "This process explains why we may see the impacts ... on wildlife later in the winter after animals have been ingesting the toxin for months on end."

And then there is the seagull, which can travel very far due to a combination of strong flying capabilities, following fishing boats for scraps of food and landing on them or something else drifting about to rest. That allows seagulls to travel farther from their home bases than many other birds.

Far, far away there may be a red tide the seagull and other seabirds get exposed to, then head back sick. This means that we may see impacts from blooms that are never in Southwest Florida's waters.

Marine and freshwater researchers are finding the health effects of a red tide or blue-green algae bloom are bad enough that the “h” in harmful algae bloom may need to be capitalized for emphasis. That's according to me, by the way, not the scientific community.

A decade ago, a literature review found few peer-reviewed scholarly works on the specifics of the harmful components of harmful algae blooms, especially focused on Southwest Florida. That has changed.

An article in the peer-reviewed journal eBioMedicine last year was a meta-review of research into harmful algal bloom aerosols and their effects.

“The health burden of HAB aerosols is likely to be considerable,” the authors wrote. “One study estimated that approximately 15% of global asthma cases are attributable to the inhalation of aerosolized HAB toxins in coastal regions, while another work found that the 2012 red tide blooms in Florida were linked with approximately 11,000 hospital admissions and 4,000 emergency department visits.”

And in the February issue Harmful Algae: “Many southwestern counties in Florida implement beach ‘Do Not Swim’ advisories, fishing restrictions, and even ban seafood and shellfish harvesting and consumption during Florida red tide blooms.

"Particularly harmful about K. brevis are the toxic neurotoxins, called “brevetoxins,” it can release of which many people are unaware. These brevetoxins can cause disturbances to sodium channels and therefore nerve issues in both marine life and humans,” the researchers wrote. “The harmful effects of Florida red tide are substantially less fatal to humans than they are to marine life, but nevertheless, the brevetoxins can cause severe health issues.”

And it appears concerned folks are no longer waiting for the right mix of politicians in the Florida Legislature to get serious about harmful algae blooms.

Late last month, we wrote an article about a coalition of environmental groups that petitioned the Environmental Protection Agency to use its authority under the Clean Water Act to step in and set water-quality standards to protect Florida’s residents, visitors, and wildlife from the health dangers posed by harmful algae blooms

It was the latest maneuver by environmentalists who say they have been trying for years to get state environmental officials to do something substantive about the growing problems of toxic red tide along the coasts and blue-green algae, also known as cyanobacteria, throughout inland waterways and lakes.

Florida Gov. Ron DeSantis has established separate task forces to study blue-green algae and red tide, but critics say the governor then ignores the two teams’ recommendations.

He may, or may not be doing that. He never got back to us when we contacted his office to ask.


Florida Fish and Wildlife Conservation Commission sampled for the red tide organism, Karenia brevis, and it was nowhere about, as you already know if you read the top of this report.

No reports of fish kills suspected to be related to red tide were received over the past week, nor was there any respiratory Irritation reported in Florida over the past week related to the harmful algae bloom.

The two birds that didn't make it due to red tide poisoning at the Clinic for the Rehabilitation of Wildlife were an adult laughing gull and a ruddy turnstone. They died within 24 hours of being admitted. An adult great egret and two juvenile double-crested cormorants were also admitted and were still in care.


It seems every day the Florida Department of Health is able to rescind a health alert for blue-green algae somewhere along the Caloosahatchee River they announce a new one in a different place.

So be careful anywhere along the river where you might get wet, and think twice about swimming in it.

The agency reminds the public all the time that winds and tides tend to push the components of blue-green algae around, so people in that region should be watchful for the potentially toxic bloom.

Satellite imagery of Lake Okeechobee saw about 300 square miles of the surface covered with moderate blue-green algae on June 6, but clouds were in the way during subsequent passes so for now 300 square miles is where it stands.

The Florida Department of Environmental Protection also makes a point of reminding all of us the on the Big Lake it is important to remember the blue-green algae potential is subject to change due to rapidly changing environmental conditions or satellite inconsistencies.

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 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.

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 like something with a naturally unpleasant odor has now started to rot, too.

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 FDEP 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 right away.

What causes blue-green algae?

Blue-green algae blooms occur when the algae that are typically present grow in numbers more than normal. Within a few days, a bloom can cause clear water to become cloudy.

Winds tend to push the 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.

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