What is red tide? Inside the toxic phenomenon destroying Florida’s marine life

(Photo by Joe Raedle/Getty Images)
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(Photo by Joe Raedle/Getty Images)

Credit: Joe Raedle

Credit: Joe Raedle

Florida is experiencing its most toxic red tide in more than a decade, decimating at least 120 miles of its Gulf of Mexico coast since November 2017.

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According to officials with the Florida Department of Environmental Protection, thousands of dead marine animals have been found washing up on the state's beaches.

"Since Sunday, 10 dead Goliath grouper, the massive reef fish that can live four decades or more, have floated to the surface," the Miami Herald reported this week. "At least 90 sea turtles have been found stranded as the tide stretches well into nesting season. And  onTuesday, as hundreds of residents packed a standing-room-only Cape Coral yacht club to hear about the federal government's efforts to deal with water conditions, a dead manatee washed up at a nearby boat ramp."

According to the National Oceanic and Atmospheric Administration, red tide refers to a "harmful algal bloom."

These harmful algal blooms occur when algae colonies grow out of control and produce toxic consequences (typically the toxic phytoplankton, Karenia brevis) on marine life, birds and people. The growth can even make it difficult to breathe the surrounding air.

These toxins often cause eye irritation, respiratory issues, asthma and can sometimes kill.

“As the name suggests, the bloom of algae often turns the water red,” according to the National Oceanic and Atmospheric Administration, though officials note scientists prefer the term harmful algal bloom over red tide.

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Are all algal blooms harmful?

Absolutely not. Most algal blooms are actually beneficial and function as a significant source of food and energy for marine animals.

What’s up with this year’s harmful algal bloom?

Both Florida and Texas face red tides annually, but the effects of this year’s red tide are unprecedented.

Officials have called it the worst red tide since post-Hurricane Katrina in 2006, which killed more than 250 manatees over a year and a half.

Since last November, nearly 300 sea turtles have already died and several other animals (fish, pelicans, manatees, a whale shark) have also washed up. Officials predict the bloom will last until 2019.

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According to the Miami Herald, Sanibel, Florida, Mayor Kevin Ruane "blamed the tide on a perfect storm of coastal pollution and a hot Gulf ignited by flushed nutrient-laden water from Lake Okeechobee," conditions that only make the problem worse, he said.

Hurricane Irma may have played a role in this year's damaging bloom. NASA scientists have previously noted that hurricanes likely help create more red tides on the Florida coast by creating a lot of runoff and dropping groundwater nutrients born far out at sea into coastal waters. Such nutrients, including nitrogen, encourage harmful algae growth.

"Wildlife is the canary in the coal mine," Heather Barron, a veterinarian and research director at Sanibel's CROW Clinic wildlife rescue center, told the Miami Herald. "It's the thing telling us your environment is very unhealthy and as a human species you need to do something about it."

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How does climate change affect red tides?

While the extent of climate change’s influence on the blooms isn’t clear, freshwater algal blooms are known to thrive in warm waters.

Timothy Davis, associate professor of biology at Ohio's Bowling Green State University, told the New York Times that climate change's warmer temperatures and higher rainfall will likely intensify the blooms.

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“We’re expecting to see larger blooms that last longer and could potentially be more toxic,” he said.

"Climate change will lead to higher air temperatures which can have a corresponding effect on raising water temperatures," the EPA website states. "Higher water temperatures combined with increased stormwater runoff of nutrients can result in conditions favorable for algal blooms. Consequently, with a changing climate, harmful algal blooms can occur more often, in more fresh or marine waterbodies, and can be more intense."

Learn more about climate adaptation and harmful algal blooms at epa.gov.

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