Florida’s early and severe red tide raises concerns for coastal bird safety


Dead fish pile up like sand dunes in Tampa Bay. Holley Short has watched them for weeks with growing apprehension. Whenever a shorebird attacks one of the carcasses, it wants to chase it away. “These are really easy selections for them. But it’s so dangerous for their health, ”she said.

As a shorebird project manager for Audubon Florida, Short is in charge of monitoring several Black Skimmer nesting colonies, as well as populations of bay terns, pelicans and cormorants. Normally, she worries that beachgoers and their pets accidentally disturb skimmer nests. This year, fish bathed in toxic algae are on his list of concerns.

Harmful algae blooms, also known as HABs or “red tides”, occur when toxic algae become highly concentrated in ocean waters. Tampa Bay is currently in the throes of an intense bloom, which resulted in the removal of more than 900 tonnes of dead fish and other marine debris from beaches last week, according to the Pinellas County Solid Waste Department. The tide currently extends from Pasco County to Cape Coral. As the situation worsens, dozens of organizations have called on Florida Governor Ron DeSantis to declare a state of emergency.

Red tides have been reported off the coast of Florida since the 16th century, and they’ve probably been around for much longer. But four of the five most enduring red tides on record in Florida have occurred in the past three decades, including the devastating 2018 bloom that killed some 2,000 tons of marine life and cost an estimated $ 8 million in tourist losses. . “It’s a natural process, but I think it has intensified in recent years,” says Mark Rachal, manager of the Sanctuaries on the Audubon Coastal Islands in Florida.

This year’s red tide is remarkable both in its severity and in its timing. Harmful algal blooms usually do not appear until early fall and disperse in January. Experts say it’s unusual and disturbing to see one so early in the season, when it can affect nesting birds and have plenty of time to intensify before the cooler weather starts.

Fortunately, Short has yet to see any signs of red tide poisoning in any shorebirds she watches. She attributes a change in the diet of the birds. “We have seen many adults bringing freshwater fish to their chicks over the past two weeks,” she says. Either way, she plans to keep a close watch on the birds, especially given the hundreds who perished in the 2018 red tide.

But not all bird populations have remained unscathed. The Seaside Seabird Sanctuary has hosted more than 100 birds, including cormorants, gulls, pelicans and herons, made ill by the toxin since June. They are not able to save them all, but they have rehabilitated most of those who enter. Many are back in full health and ready for release, says Melissa Edwards, director of the Seaside Seabird Sanctuary Bird Hospital in Indian Shores, Florida. But with the intensification of the red tide, she said, “we haven’t felt comfortable doing it yet.”

Much like a hurricane, the severity of a harmful algal bloom is determined by a confluence of factors, says Barb Kirkpatrick, executive director of the Gulf of Mexico Coastal Oceans Observing System. This year these included a perfect storm of pollution, drought conditions, strong winds and ocean currents.

Between March and April, the Piney Point fertilizer plant dumped more than 200 million gallons of nitrogen-rich runoff into Tampa Bay to prevent a leak at the facility from flooding the nearby community. . Hundreds of residents were forced to temporarily evacuate over Easter weekend, and the incident sparked outrage from environmental groups. Nitrogen is one of the essential nutrients that toxic algae need to thrive. While this event did not directly cause the bloom, it almost certainly contributed to its severity, say Kirkpatrick and Rachal. Winds and ocean currents from Tropical Storm Elsa also spread the microbes along the Florida coast, where they combined with another burgeoning red tide to the south. Warmer-than-average months of March and April could also have played a role in this year’s early flowering schedule. In the coming decades, scientists fear that warming oceans will continue to make red tides longer and more frequent.

Like many harmful algal blooms in the Gulf, the Tampa Bay red tide is caused by a microscopic organism called Karenia brevis, which creates a myriad of concerns for wildlife and coastal populations. When waves break along a shore, the organisms separate and release toxins, called brevetoxins, which can affect brain, nerve, and respiratory functions in vertebrates. “They are very fragile,” says Lorraine Backer, an environmental epidemiologist with the Centers for Disease Control, who helps assess algal blooms harmful to the agency.

In water and sea foam, the toxin creates a dangerous soup. Exposed fish die quickly, their gills paralyzed. Eating contaminated fish or shellfish can be harmful to birds, dolphins, and land mammals, including humans. While shorebirds like skimmers and terns are most likely to be affected, wading birds are also vulnerable. They can lose their motor functions and “seem almost drunk,” Edwards says.

Brevotoxins can also be airborne when fragments of organisms are trapped in tiny bubbles of sea spray. In this form, they pose a relatively low risk to humans and terrestrial wildlife, but still keep people away from the beach. They can trigger allergy-like symptoms, such as watery eyes, runny nose, itchy throat or, in more severe cases, difficulty breathing. “People with asthma may experience their symptoms longer, even after leaving the beach,” Backer explains.

NOAA is now monitoring wind patterns and the concentration of these airborne particles for its experimental red tide forecast, which currently has many beaches around Tampa Bay in the high-risk category. Although Short does not consider herself susceptible to respiratory symptoms, this year she has experienced the effects firsthand. “It’s like you have a cold or something, but you don’t have one,” she said, “I knew when I started having all of these symptoms that it was pretty serious.”


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