How Long Does Florida’s Red Tide Normally Last

Thousands of dead fish, numerous turtles, manatees, and even sea birds. have been washing up on the beach in Southern Florida where Karenia brevis, microscopic toxic algae that make up the Harmful Algal Blooms (HAB) turning the water off the coast of Florida Red. The Red Tide causes toxins called Brevetoxins that leave the ocean depleted of Oxygen and poisoned also creating airborne toxins that can hurt humans and marine life. How long does Florida’s Red Tide Normally Last?

Normally, Florida’s naturally occurring Red Tide species, Karenia brevis (HAB) begins in the late summer or early fall & lasts through the winter until February or March, where it dissipates because of sustained winds, lack of nutrients or predators.

Red Tides have been around for hundreds of years and are a typical sight every year in this area of Florida. But for the last 20 years, the massive Algal Blooms are dissipating slower, especially since 2018’s season’s, according to the NOAA who forecast and Update the movement of the Red Tides and monitors daily on their Web Site called Red Tide In Florida and Texas.

When is Red Tide Season In Florida


There are early reports of this natural phenomenon called Red Tide in the Gulf Of Mexico region of Florida, documented as early as the 1500s in Captains logs from Spanish explorers that described the same kind of symptoms of their crew, as people describe today from the coastal areas of Florida.

Sneezing, coughing, and watery eyes along with red color and dead fish. The first sample was taken from the Gulf in 1844 but the organism that causes the algae wasn’t discovered and named Karenia brevis until 1944. Florida’s Red Tide was around long before humans and industry populated the coast.

Karenia brevis blooms occur in the Gulf of Mexico almost every year, generally in late summer or early fall. They are most common off the central and southwestern coasts of Florida between Clearwater and Sanibel Island but may occur anywhere in the Gulf. Red Tide shows up in Fall around September but is normally at its peak in November.

The concentrations at this time can be 1000 cells per liter or less and are 25 to 45 micrometers long and 15 to 20 micrometers deep. Other times it could be many more. They are able to move through the water by themselves and tolerate salinity and temperatures that are prevalent in the ocean. In Florida, blooms more frequently formed miles offshore of the southwest coast of Florida between Tampa Bay and Naples.

Occasionally a harmful algal bloom that’s formed offshore the west coast of Florida is transported to the east coast by ocean currents. Every few years blooms may also form offshore the Florida Panhandle. In Texas, blooms are most frequently reported in the Port Aransas and South Padre Island regions.

Red Tides start in nutrient-poor water between 11 and 46 miles offshore. The population of Karenia brevis move into the area and populate heavily. Within a few weeks, concentrations are so heavy that there big enough to kill fish. Wind and current control the movement and push it towards land.

The mass can be fed by nutrient runoff from land making it become much larger. A bloom can linger in a coastal area for weeks or months, eventually be broken apart by wind, current, and ocean, then the population of the algae is dispersed. Since records have been maintained in Florida, they show that some years are worse than others and some years are better for occurrence but with no solid rhyme or reason.

How Long Does Red Tide Last

Vincent Lovko, staff scientist and program manager for Phytoplankton Ecology at Mote Marine in Sarasota, Florida said the Red Tide season is typically from late summer to late fall. Scientist say from September to October is typically when red tides reach their peak of severity and then disappears.


There is a concern across the coastal communities that this year’s bloom in 2019 will be worse as conditions ripen for it. the Bloom that happened in 2018, 9 months ago is still growing and shows no signs of slowing down.

There have been blooms in the last decade or two, where they have lasted more than one year and then stopped. This one in from 2018 is somewhat different and scarier because of it’s an ongoing threat to aquatic life and growth.

How and when a red tide bloom will end is difficult to predict. A good storm with enough wind and rain can break up a bloom and push it out to sea, “but that doesn’t always work,“ Lovko said. “In 2012 we had a remnant of a hurricane come through and broke it apart, but it came back and was one of the worse we’ve seen.”

Most people in this area of the Country agree that it’s the nutrients that are natural or man-made that feed the bacteria and then increase the population that enables the Red Tide to have a longer season. Not everybody agrees with why this is happening. Some Officials believe the many estuaries around the Gulf in Florida mainland are the source of nutrients that are feeding the Algae blooms, but those same nutrients are feeding the fish in the ecosystem around Florida.

The blooms start too far offshore for anything onshore to determine their size and longevity. Other reasons have been looked at like runoff from Lake Okeechobee and worldwide Climate Change.

Researchers have studied nutrients that have been dragged miles away offshore to feed the algal blooms by hurricanes that have developed in the area the last few years.

The only thing they are sure of is that the Karenia brevis algal blooms are getting worse and the Brevetoxins that come with them are doing increasing damage. This alga can actually feed off of other algal blooms. There could be a huge different type of algal bloom in the Gulf and the Red Tide could be using that as a food source.

It can inhibit the growth of other algal blooms. Eat all the food that other species need to survive, Karenia algal bloom can use numerous types of nitrogen where if you take one source away it will find another way to eat.

Karenia Blooms have the ability to kill fish even though the fish don’t use it as a food source if there is a lack of phosphorus in the water, Red tide algae have the ability to turn on or turn off its toxins emitters.

So when it runs out of food namely phosphorus it can turn it’s toxins emitters on, kill fish that will eventually provide plenty of the new food source, creating their own source of nutrients if necessary.

This makes them a pretty powerful self-sustaining entity in the ecosystem. They could be dangerous aquatic organisms. Very hard to get rid of in the right circumstances. There is some scientific proof that the Karenia brevis algae learned to feed off other bacteria.

With a density in population and constant nutrients being washed out to shore, along with Florida being a perfect haven for these algae to grow numerous and free, this makes many people believe the Red Tides season is increasing in frequency size and duration and more dangerous here and will be a danger around the globe in the future.

Is A Red Tide Harmful To Humans


It’s well known that Red Tide can cause Respiratory Irritations. Karenia brevis produces a Neurotoxin that’s called Brevetoxins, that is released from the cell to the water. The ocean or bay’s agitation can break the walls of the algae cell and releases this toxin into the water. Then when a person inhales the sea spray that is caused by the ocean water, coming off the beach they inhale the toxin.

The toxins have been measured as far inland as 1 mile. Common symptoms of inhaling this toxin are coughing, sneezing and watery eyes. The symptoms are confused with an allergic reaction so Health Officials have stated that in order for you to experience the toxins from the Karenia brevis you have to have actually had contact with it.
Some people are more sensitive to toxins than others.

Once the person leaves that area where the toxins are having an effect on them the symptoms will clear up and go away. People who suffer from a chronic respiratory illness like Asthma or COP, should try and make an attempt to stay away from the beach during a Red Tide alert.

Some people could have a very hard time dealing with it. There are studies showing that Red Tide could lower immune systems to other illnesses such as Bronchitis, pneumonia, and asthma that can be triggered by the Red Tide. To feel the effects of Red Tide at the Beach you must have 3 things that are necessary. You must have:

  1. A high enough Algae Bloom Level
  2. Wave Action
  3. Wind blowing Sea Spray in your direction

Most people who get sick, probably wouldn’t even know that Red Tide is in their area. Conditions along the coast change hour to hour so residents need to take some precautions. Health Officials recommend using air conditioners when indoor and even wear a paper mask to cover your face when you’re down near the beach. This will ensure that you have no contact no sea spray

Rashes and skin irritations have been reported by people that swim in Red Tides, but again that would depend on the person being sensitive more than other people. Health Official recommend rinsing off in the shower as fast as you can if you make contact with it.

Florida Red Tide causes Neurotoxic Shell Food Poisoning. (NSP) Are now known to cause by eating contaminated Shell Fish like oysters, whelks, clams, and mussels.

Fish kills happen when the Red Tide is at medium to high levels. Bottom fish are normally the first to be affected. Not poisoned. Brevotoxin paralyzes fish by keeping them from swimming so they can’t breathe. Fish need to swim in order to breathe. It is very possible that in the backwater bays where there is lower oxygen content and algal blooms that there won’t be enough oxygen for the fish to survive in and they will also die.

The Red Tide’s Karenia brevis are good at survival they move into different levels of the water in the daytime using the sun for photosynthesis and at night at the bottom where there are more nutrients and more protection.

Is Red Tide Harmful to Pets?

Animals that swim in water with algae blooms may experience illness similar to their owners, and worse, depending on the amount of toxin they are exposed to.
Symptoms include increased drooling, loss of appetite, skin rashes, trouble walking, weakness, vomiting, diarrhea, numbness/tingling, difficulty breathing, heart and circulatory problems, convulsions, loss of consciousness, and death.

This may happen with little time for owners to respond. If your animal shows any of these signs after contacting a bloom, please see your veterinarian.
Pets, domestic livestock, and wildlife should not swim in or drink water where an algal bloom, discolored water, or foam is present. Remember, algal blooms can present in shades of bright green, brown, red, orange, purple, and yellow or other colors.

Sometimes algal blooms are reported to resemble spilled paint in the water due to their bright colors.
Pet owners should report any severe illness to their veterinarian immediately.
Pets that have been exposed to a bloom should be washed with clean clear water quickly before they have a chance to lick their fur.

What causes harmful algal blooms?


What is HAB’s?
In every natural body of water on Earth, there is a tiny one-celled organism floating just beneath the surface called phytoplankton. Phytoplankton use chlorophyll to collect sunlight just like land plants, but instead of making large trees, phytoplankton makes lots of single cells that float around in the water. When nutrients are available in the water they will use this as food.

If they have enough to eat they will multiply very quickly. When there is an abundance of this happening in nature it’s called a bloom. Most of this phytoplankton in a natural setting is healthy and are used up as food for fish and other aquatic life. There are a few species of phytoplankton that can make fish and animals sick and die. Out of 5,000 known species, there are 100 known to be toxic. These algal blooms can be any color besides the Red tides here in the Gulf of Mexico.

A scientist has named these algae Harmful Algal Blooms or HABs.  Scientist have noticed that there is an increase in these blooms in recent years. The increase in frequency is a major concern. Not only a public health concern but a concern to commercial and recreational fishing industries. This hurts tourism and the likelihood of residents on the coastal communities where these Red Tides show up. Karenia brevis is one of the most common HABs on the Gulf Coast today.

In the Gulf of Mexico, algal blooms are caused by the rapid growth of the microscopic algae species like Karenia brevis (commonly called red tide) but they are only one of many different species.

Red tide can cause respiratory illness and eye irritation in humans. It can also kill marine life. Blooms are often patchy, so impacts vary by beach and throughout the day.

NOAA monitors conditions daily and issues twice-weekly forecasts for red tide blooms in the Gulf of Mexico and East Coast of Florida. You can find up-to-date information on where an algal bloom is located and a 3–4-day forecast for potential respiratory irritation by selecting a region on their locator. This information may help you find an unaffected beach if you are visiting the coast.

NOAA’ Harmful Algal Bloom (HAB) operational forecast system in the Gulf of Mexico identifies whether or not a bloom of algae will contain a toxic species how big it is, where it’s headed and if it’s likely to be trouble down the road. Or down the Coast, I should say. It works similar to a weather forecast and provides coastal towns and their officials the details on what may happen with the mass of algae.

The towns where this phenomenon may be affected will have to make decisions based on the information it gets, whether to close beaches or discontinue shell food harvesting. They can do this with more accuracy and be a little more precise and saving money at the same time. The system relies on satellite imagery, field observations, buoy data, health reports and models in order to create information on Bloom events.

Forecast are created by Public HAB conditions reports using the data to create the likelihood of a respiration irritation or other health impact on the people who live in the area along the coast.

Expert Oceanographers from NOAA go over the updated reports and analyze everything. To ensure the highest degree of accuracy, all operational HAB forecasts undergo secondary review prior to dissemination. Because of the Blooms in the Gulf of Mexico,

Scientist believe that we should be monitoring places of interest around the world. This Red Tide could be an extension of new and more dangerous problems we will face on the horizon because of Global warming and the changes it’s making to our Earth’s Oceans. 

Related Questions:

How often does red tide happen?

Karenia Brevis blooms or Red Tides occur in the Gulf of Mexico almost every year, generally in late summer or early fall.

Is red tide natural?

A red tide is caused by an increase in the population of Karenia Brevis microscopic toxic algae. This natural alga has been around for hundreds of years.

Can red tide damage your lungs?

This algal toxin commonly inhaled in sea spray, attacks and damages human lungs causing lung irritations.




When will the Red Tide Go Away-Tampa Bay Times Sept 2018

Jim has over 30 years of experience in Water/Wastewater Treatment & Water Filtration Business as a Consulting-Operator. He has written over 300 articles on the World-Wide Water Situation. 


Editor/Author, MyWaterEarth&Sky

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