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Why Is Florida's Red Tide Outbreak So Bad Right Now?

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It’s been a summer of algae for the Sunshine State. Last month, Governor Rick Scott declared a state of emergency in counties whose waterways were befouled by blue-green algae blooms. On Monday, Scott found himself declaring another emergency for a separate red tide algae outbreak taking place across the state.

The current red tide bloom developed last November off the coast of southwest Florida and is now in its tenth month. High concentrations of algae have been measured in coastal waters from Tampa Bay to Sanibel Island, where 267 tons of marine life have washed up dead since July, according to the Guardian.


So, why is this algae outbreak so bad?

Robert Weisberg, an oceanographer at the University of South Florida whose lab produces seasonal and short term forecasts of red tide, told Earther a confluence of ocean circulation and environmental factors are likely responsible for initiating the bloom. Others experts are pointing to the potential role of human-driven nutrient pollution in helping to maintain it.


The neurotoxin-producing algae responsible for the carnage, Karenia brevis, is found naturally in marine and estuarine waters off Florida, and blooms occur on the regular in the late summer and early fall. Weisberg explained nutrient availability is the key factor behind whether K. brevis can get a foothold in an area of the ocean known as the West Florida continental shelf. His research has shown that deep upwelling of nutrient-rich waters onto the continental shelf—driven by the Gulf of Mexico loop current—encourages growth of the algae’s competitors, keeping red tide concentrations low. But when the loop current shifts, fewer nutrients rise to the surface, and red tide can gain a foothold.

That, Weisberg told Earther, is exactly the oceanographic setup that’s been in effect over the past year. Ocean currents then carried the toxic bloom to the coastal areas and beaches where it has been wreaking havoc since. His team started predicting a bad summer for red tide back in June.

Once a bloom gets to the shore, it can kill fish, which decay and help sustain it. Many experts think nutrient runoff from agriculture and other human activities can also play a role. But while the blue-green algae blooms that pop up regularly around Florida’s Lake Okeechobee are clearly initiated by runoff, that isn’t the case with red tide events that start offshore.

Still, it’s possible nutrient runoff is helping fuel these blooms once they reach the shoreline, one complication being that K. brevis is a saltwater organism, and too much freshwater discharge can negatively impact their growth.


“The term ‘messy’ has been used when it comes to trying to understand the different nutrient sources that sustain these blooms,” Steve Davis, an ecologist at the Everglades Foundation, told Earther.

Florida Sea Grant director Karl Havens thinks that on balance, nutrients delivered to the Gulf Coast this year following heavy spring rains and water discharges from the lake did help fuel the red tide. Davis pointed out there could also be indirect effects. For instance, nutrients could help fuel the growth of other algae that K. brevis can actually graze on.


Unfortunately, as the Miami Herald notes, water quality monitoring that could help elucidate connections between human-caused pollution and red tide events has been cut under Scott. The paper reports that a coastal network of 350 monitoring stations has shrunk to 115, with the cuts including a station at Pine Island Sound experiencing the brunt of the red tide fish kills.

Recent injections of emergency funds are unlikely to make up for this loss of long-term monitoring capacity. And Weisberg, for one, believes the money that is going toward red tide monitoring could be much better spent. He says the community needs resources to sample offshore where the blooms form, something Scott’s latest emergency funds won’t facilitate.


“I’ve been contacted by absolutely no one that has resources to possibly contribute,” he said. “It’s been very frustrating.”

As if to underscore the need to understand red tide better, nobody can say when the current crisis will abate. Red tide “season” typically doesn’t begin until fall, and communities are going into that season with a bad bloom already underway.


“We have no idea what it’s going to look like in the coming months at this time,” a spokesperson for Florida’s Fish and Wildlife Commission told Earther.

Weisberg was a bit more definitive. “This year is bad, and I think it will get worse,” he said.