Code Red

While Florida’s East Coast is currently dealing with water quality issues stemming from the diversion of tainted water to protect sugar cane crops, almost every year Florida’s Gulf Coast is affected by a naturally occurring harmful algal bloom. Commonly known as red tide, Karenia brevis is a species of algae that can cause catastrophic damage to our state’s marine ecosystems and local economies. When the organism moves into an area and multiplies in higher-than-normal concentrations, a release of brevetoxins can not only cause harm to people, but also lead to widespread fish kills and poisoned waters for a variety of marine animals.


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FWC Fish and Wildlife Research Institute

Long-term forecasts for red tide can be unreliable, so organizations like the FWC and NOAA instead give weekly updates based on test results from samples taken around the state.

From late summer to early fall, the Karenia brevis cells that make up red tide are commonly found in the waters of central and southwest Florida, generally between Apalachicola and Sanibel Island. Karenia brevis cells can be present year-round in Gulf waters in background concentrations, meaning there are 1,000 or less cells per liter and pose no threat at all. These cells become harmful, however, when they bloom in higher concentrations and make their way inshore.

Scientists have determined that red tide originates in nutrient poor water that exists upwards of 50-miles offshore. These dead zones are low in oxygen content and when wind and current move concentrations of these single-cell dinoflagellates inshore, they can then bloom and develop to the point where natural resources are harmed

These seasonal outbreaks develop in four stages. The first stage is called the initiation stage, which consists of Karenia brevis cells accumulating and moving into an area. Next, in the growth stage, the concentration increases and within a few weeks can be large enough to kill fish and other marine life. After that in the maintenance stage, wind and currents control the bloom as it continues to render damage on the surrounding ecosystem. Blooms that move close to shore are known to expand due to nutrient runoff from land. Finally in the dissipation or termination stage, winds and currents disperse the cells and introduce new water that reduces the concentration of cells or moves the bloom entirely to a different area.

Because of the gravity of the situation, the FWC produces weekly red tide reports from samples collected across the region. As of press date, the FWCs latest update on the current status of red tide, only two of nearly 100 samples collected and tested showed presence of Karenia brevis cells in southwest Florida’s coastal waters. Both of the samples were from Charlotte County, but contained only background concentrations of cells. Further testing on samples from the northern Gulf showed no evidence of any cells.

After sampling results were reported to the FWC, Florida Department of Health and Florida Department of Agricultural and Consumer Services, it was determined that the official level of toxins in our state’s waters was “low to extremely low.”

The lack of red tide cells among Florida’s coastline this year is comforting, but beaches, lakes, rivers and estuaries have still suffered at the hands of a different culprit. In this case, cyanobacteria that originated in Lake Okeechobee washed onto Florida beaches after making its way through rivers and estuaries, harming local marine wildlife and residents, as well as negatively affecting the local economy as tourism withstood a substantial downturn.

Although not red tide, this blue-green algae still releases toxins that have resulted in the deaths of countless fish and marine mammals. Furthermore, multiple cases of people experiencing nausea or rash from exposure to the toxic algae have been reported.

According to the FWC, controlling these harmful algal blooms is a complicated matter. Since the toxins are actually released when the organisms die, simply killing the microscopic invaders does more harm than good. While scientists are researching different strategies in helping control the situation, the difficulty comes in finding a method that does not hurt the surrounding environment.

In the 1950s the U.S. Fish and Wildlife Service attempted to kill red tide cells using copper sulfate, hoping that it would also prevent the release of the harmful brevetoxins. This attempt was very much unsuccessful, as the addition of the copper sulfate failed to prevent the release of the toxins and had an additional destructive effect on marine wildlife.

Since, scientists have continued to swing and miss in trying to keep the cells from releasing these harmful toxins. They have, however, found ways to reduce shellfish toxicity during these harmful blooms.

This research could prove vital, as consuming shellfish that have been exposed to the toxins released during a bloom can be dangerous. Ingesting these toxic shellfish can lead to a case of neurotoxic shellfish poisoning, bringing about symptoms including nausea, vomiting, slurred speech and dizziness.

The FWC states that the best way to avoid contracting this sickness is to eat shellfish that have only been harvested commercially, since they are tested for brevetoxins once they are captured. Additionally, state law prevents the recreational harvest of shellfish in areas affected by red tide, so be sure that you are fully aware of the conditions and regulations in surrounding waters before going diving for dinner.

Long-term forecasts for red tide can be unreliable, so organizations like the FWC and NOAA instead give weekly updates based on test results from samples taken around the state.

Although the latest updates and weekly forecasts show that the presence of red tide cells state-wide is minimal and won’t cause any harm or damage, that can certainly change. It’s in your best interest, especially if you spend time in the notorious red tide stomping grounds of central and southwest Florida, to stay updated on weekly test results and predictions. Furthermore, just because red tide isn’t currently present does not mean that Florida’s waters are free of all algal blooms.

The solution will take a generation to fix if it is ever to be done. The natural flow of water from the Kissimmee River, into Lake Okeechobee, then into the Everglades needs to resume. The sugar farms need to be converted back to marshland that allows sheet flow of water. Engineering-wise, it is a nightmare and the dollars would be astronomical, but the end result is the only solution for returning the system to as close to what it was before we began farming the land.

We must be mindful of the toxic blue-green cyanobacteria blooms that continue to affect beaches and inland waterways on both the Atlantic and Gulf Coasts. To learn more about or report cases of red tide, visit