How Long Does Red Tide 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 Red Tide Last?

Normally, Florida’s naturally occurring Red Tides called Karenia brevis last 5-6 months beginning in the late summer/early fall & lasts through winter until February/March, where it normally dissipates because of sustained winds or lack of nutrients to feed on.

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 the 2018’s season, according to the  NOAA forecast and Update the movement of the Red Tides and monitors daily on their Web Site called Red Tide In Florida and Texas.


How Long is Red Tide Season In Florida


What Is a Red Tide? | NOAA SciJinks – All About WeatherThere are early reports of this natural phenomenon called Red Tide in the Gulf Of Mexico region of Florida waters, documented years ago 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 section 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 previous to humans and industry populated the coast.

Karenia brevis blooms causing Red Tide that occurs in the Gulf of Mexico almost every year, generally in late summer or early fall. They are most common on the central and southwestern coasts of Florida between Clearwater and Sanibel Island but may occur anywhere in the Gulf.

Red Tides show up in Fall around September but are normally at their peak in November. The Harmful Algae bloom can last anywhere from a few days to three to five months and sometimes longer in Florida waters once a year.

The concentrations of tide toxins Karenia brevis 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, red tides more frequently formed miles offshore of the southwest coast of Florida between Tampa Bay and Naples.

Occasionally red tide a harmful algal bloom (HAB) that’s forms mostly offshore pollution on the west coast of Florida red tide is transported to the east coast by ocean currents. Every few years blooms may also form offshore at the top of the Florida PanhandleIn Texas, blooms are most frequently reported in the section of Port Aransas and South Padre Island regions.

Red Tide starts 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 many species of fish and affect shellfish and other marine wildlife. Wind and current control the movement and push it toward land.

Red Tide can be fed by nutrient runoff from land making it become much larger. A harmful algal 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 ago are worse than others and some years are better for red tide occurrence but with no solid rhyme or reason.


Red Tide Karenia brevis 


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. He also said from “September to October is typically when red tides reach their peak of severity and then disappears”

“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 waters.

The red tide 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 harmful algal blooms by hurricanes that have developed in the area in 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 water and Florida waters and the Red Tide could be using that as a food source.

It can inhibit the growth of other (blue-green) algal blooms until everything dies. Eat all the food that other species need to survive, Karenia algal bloom can use numerous types of nitrogen and other nutrients according to research, so if you take one source away it will find another way to eat.

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

So when it runs out of food namely phosphorus it can turn its toxins emitters on, and kill marine 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 the shore, along with southwest Florida water being a perfect haven for these algae to grow numerous and free, this makes many people believe the Red Tide season is increasing from past years in frequency size, and duration, the event more dangerous from the past here in Florida’s waters and will be a danger around the globe in the future.


Red Tide Blooms 


It’s well known that Red Tides in Florida waters can cause Respiratory IrritationsKarenia Brevis produces a Neurotoxin that’s called Brevetoxins, which is released from the cell into 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.

Red tide in Manatee County in 2021: 9 things to know | Bradenton HeraldThe 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 in the Red Tide season.

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. Respiratory irritation and other conditions and information along the coast from the latest red tide pollution forecast news can change from hour to hour so residents need to take some precautions.

Health Officials recommend using air conditioners when indoors and even wearing 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 tide toxins, but again that would depend on the person being sensitive more than other people. Health officials 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, there won’t be enough oxygen for the fish to survive and they will also die.

The Red Tide blue-green algae are good at survival they move into different levels of open water in the daytime using the sun for photosynthesis and at night at the bottom where there are more nutrients and more protection. They can survive anywhere from a few days to three to five months and in Florida for more than a year.


Is Red Tide Harmful to Pets


Animals that swim in water with algae blooms may experience illnesses similar to their owners, and worse, depending on the amount of toxin they are exposed to.

Red Tide 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 being in contact with tide toxins or an algae 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 during Red Tide. Remember, algal blooms can present in shades of bright green, brown, red, orange, purple, 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 bloom should be washed with clean clear water quickly before they have a chance to lick their fur.


Blue Green Algae Blooms


Left: K. brevis, the species that causes red tide and associated fish kills. Right: The dominant cyanobacteria (Microcystis aeruginosa) responsible for the blue-green algal bloom in Lake Okeechobee, 2018.

Both are algae and both are in bloom this summer, but a different microorganism is to blame for each. The dinoflagellate Karenia brevis, or K. brevis, is the alga responsible for red tide, while blue-green algae are caused by different types of cyanobacteria, namely Microcystis aeruginosa, which is believed to be blamed for the massive bloom in Lake Okeechobee, according to researchers from the University of Florida.

Blooms in freshwater lakes and reservoirs are most commonly caused by blue-green algae (also known as cyanobacteria). There are several different kinds of blue-green algae that can cause algal blooms including Microcystis, Anabaena, and Cylindrospermopsis. Water samples suggest that the dominant species affecting the 2018 Lake Okeechobee bloom is Microcystis aeruginosa.

Lake Okeechobee is most prone to having large cyanobacteria blooms when the weather is warm and sunny (spring through early fall). Periods of high rainfall and tropical storms can increase the potential for blooms by stirring up nutrients in the lake bed and increasing the flow of nutrient-rich water into the lake from upstream watersheds.

Like the red tide, blue-green algae can also be harmful to humans and wildlife. Some, but not all, blue-green algae types release toxins that can kill fish and wildlife. These toxins can also have negative human health impacts. Microcystis aeruginosa is known to release a toxin called microcystin, which can result in gastrointestinal problems and possibly liver damage if contaminated water is ingested. For more information about the 2018 Lake Okeechobee algal bloom.

What Causes Harmful Red Tide Algal Blooms


What are HABs?

In every natural body of water on Earth, there is a tiny one-celled organism floating just beneath the surface called phytoplankton. Phytoplankton uses 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 these phytoplankton in a natural setting are 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 Red Tide algal blooms can be any color besides the Red tides here in the Gulf of Mexico.

Scientist has named these algae in the past Harmful Algal Blooms or HABs.  Research Scientists 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 for commercial and recreational fishing industries especially in Texas and Southwest Florida Waters

This hurts tourism and the likelihood of residents in 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 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. Do Red Tides kill marine life? Blooms are often patchy, so impacts vary by the beach and throughout the day.

NOAA monitors conditions daily and issues twice-weekly forecasts for red tide blooms in the Gulf of Mexico and the 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 its locator. This information may help you find an unaffected beach if you are visiting the coast.

NOAA’s 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 similarly 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 while 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 Algae Bloom events.

The latest forecasts are created by Public Red Tide 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 on Florida waters and analyze everything. To ensure the highest degree of accuracy, all operational HAB forecasts undergo secondary review prior to dissemination.

Scientists believe that we should be monitoring places of interest around the world. Red Tide Blooms 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.



JimGalloway Author/Editor


The University of Florida-Harmful Algal Blooms: Red Tide vs. Blue-green Algae



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