A microscopic species of algae called Karenia brevis has been growing rapidly in Florida, leaving dead fish on the shore.
Harmful “red tide” wreaks fetid havoc on Florida’s Gulf Coast, canceling spring vacations for some beachgoers, causing burning eyes and respiratory irritation in people and killing wildlife.
In recent weeks, a microscopic species of algae called Karenia brevis has been growing rapidly there in the so-called red tide, as so-called harmful algal blooms change the color of the seawater.
These blooms develop offshore and are brought closer to land by currents and winds, usually by an upwelling of nutrients from the sea floor. And they don’t just happen in Florida; Red tides can occur in sea bodies around the world, and also as a result of other types of algae, although the algae caused by K. brevis are particularly harmful to humans and wildlife.
There is no certain answer as to when this latest Florida red tide event will end. “If we’re really lucky, it’ll fade or die off over the next few weeks,” said Richard Stumpf, an oceanographer with the National Oceanic and Atmospheric Administration (NOAA) who studies harmful algal blooms. “If we’re not so lucky, it may take longer.”
Because red tide conditions can change from day to day, it’s important to keep up to date if you’re planning to spend time on the water or on the beach anywhere. Here are some answers to frequently asked questions about Red Tide:
What causes red ride?
Red tides occur naturally and have been documented around the Gulf of Mexico in particular since the 15th century, said Richard Pierce, an ecotoxicologist at the Mote Marine Laboratory in Sarasota, Fla.
In particular, the algal bloom caused by K. brevis requires a complex variety of factors that are coordinated at the right time.
“The first is biology – the organism must be present in the water and outperform other phytoplankton,” explains the Mote Marine Laboratory on its website.
“The second is the right chemistry – which includes the right temperature, salinity and the nutrients it needs to grow and reproduce. The third component is the right physical conditions to concentrate and transport K. brevis. The fourth component is ecology – the presence or absence of other life forms, such as B. other seaweed that may promote or inhibit K. brevis blooms.”
When these conditions are ripe, buds will strike and the K. brevis organisms will multiply out of control.
Nutrient-laden runoff from sewage and fertilizer spills doesn’t cause a red tide, Pierce said, but it can intensify it. “If there’s a red tide in the area, it’s going to make it worse and stay longer,” he said.
How long does the red tide last?
Generally, harmful algal blooms form in the fall and can last anywhere from a few weeks to more than a year, Pierce said.
“The duration of a bloom in coastal Florida waters depends on physical and biological conditions that affect its growth and persistence, including sunlight, nutrients and salinity, and the speed and direction of wind and water currents,” according to the Florida Fish and Wildlife Conservation Commission or FWC.
A bloom will eventually “burn out” when the water is cooler, when the red tide is dissipated, and when the bloom is moved to an area with fewer nutrients it needs for reproduction, Pierce said.
A red tide in 2021 in China’s Xianglu Bay.
Can red tide make you sick?
Harmful algal blooms have been reported in all US coastal states. Those caused by K. brevis are concentrated in Florida and Texas around the Gulf of Mexico, but have also been found along the Atlantic coast to North Carolina.
K. brevis red tides are a big deal, not just because the red-brown water looks uncomfortable; The algae can also be toxic to humans and wildlife. K. brevis produces tasteless and odorless neurotoxins called brevetoxins, which are airborne and can cause eye and respiratory irritation in humans.
You don’t even have to get in the water to be affected. Just being outside near a red tide can cause symptoms.
“When I go to the beach with it, I feel like I suddenly have a cold. My nose is running. I cough. My eyes are crying. My sinuses hurt sometimes. i will leave the beach [and] 15 minutes later I’m fine again,” said Stumpf.
“People with asthma are at risk for greater health risks,” he added, noting that anyone with chronic obstructive pulmonary disease also needs to be cautious about exposure.
If you’re affected by red tide, Florida poison control centers recommend going to an air-conditioned room to relieve symptoms and seeing a doctor if your symptoms are more severe. Stumpf noted that wearing a mask can also help mitigate the risks of inhaling brevetoxins.
Exposure to brevetoxins can be deadly for animals, which is why red tides often leave smelly piles of dead fish on shore. The brevetoxins paralyze and kill fish gills, Stumpf said. “If enough is ingested, the toxin can kill birds and mammals,” he added. Just this month, a manatee was rescued in Florida from distress caused by the red tide.
Can you eat fish and seafood at high tide?
The neurotoxins produced by K. brevis can accumulate in shellfish and cause neurotoxic shellfish poisoning if ingested.
But Stumpf said it’s safe to continue eating fish and shellfish as long as you buy seafood from a reputable dealer and not off the back of a truck because the industry is closely monitored.
“Commercially available shellfish are often not harvested locally and, if harvested locally, are tested for red tide toxins prior to sale,” notes the FWC.
Can pets go outside on red tide?
As for pets, keeping them away from a red tide is better for their health.
“They are like people. If they’re on the beach with onshore winds, they’re breathing in the neurotoxins, and that’s not good for them,” Pierce said.
Also watch out for the foam that collects on the beach during red tide, as it can be high in toxins.
“Dogs in particular often lick off a fish that may be dead, lick off the foam and can become very ill. In fact, they can die from it,” Pierce said.
I am planning a beach vacation. How far in advance can the red tide be predicted?
Red Tide events have seasonal patterns. “Anyone who wants to avoid Red Tide should generally take a vacation [in Florida] would be May, June, July, August,” Pierce said. “Statistically, flowering would begin in September-October and continue through the winter, then tail off in late April.”
But if you’re planning a vacation weeks in advance, understand that it’s not yet possible to predict exactly when and where the red tide might affect specific beaches. It is best to check beach and weather forecasts for up-to-date information on red tide concentrations.
For example, the FWC regularly releases updates on red tide conditions based on K. brevis sampling. NOAA also predicts possible respiratory irritation at individual beaches in Florida and Texas based on field sampling of K. brevis concentration and factors such as wind speed.
According to Stumpf, wind direction can also help determine if it’s safe to be on shore.
“YYou could be out on the beach and never notice. I ate lunch on a beach during a severe red tide and had a wonderful lunch because the wind blew the poison across the Gulf, not inland,” he said.
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