Why tonnes of dead fish are washing up on Florida beaches
Beachgoers and tourists hoping to enjoy Florida’s sandy beaches have come across a bleak scene for the past few months: the coasts are dotted with dead fish, maggots and a toxic white foam, all brought on by a harmful algae bloom called “red tide”. The bloom, which experts say has been intensified by local pollution, has posed a severe threat to wildlife and the barely recovering tourism industry.
Since May, the western coast of Florida on the Gulf of Mexico has been impacted by a severe red tide. Local docks and beaches have become a scene of desolation, particularly after Hurricane Elsa winds in July blew tonnes of fish carcasses to the shorelines.
The outbreaks have been particularly severe in Sarasota, Manatee and Pinellas counties, located on Florida’s southern Gulf coast. More than 1,700 tonnes of fish and debris have already been collected from beaches in Pinellas County. Residents and tourists alike have been sharing photos and videos of the dismal scenes, garnering millions of views on TikTok.
Red tide is a regular phenomenon in the Gulf of Mexico caused by blooms of algae called Karenia brevis, which releases harmful toxins that can kill aquatic species as large as manatees and cause respiratory irritation in humans. Local wildlife such as birds who eat the dead fish can also be poisoned.
Everywhere the #waves wash up scene after scene of twisted #eels, #fish, and #dead sea grasses. I was told by one beach-goer the further north you go (towards Crystal River/#PineyPoint leak) the larger the dead #sealife and #fish become. #redtide #GOM pic.twitter.com/aOFRDYuwdb— Christina RadChick Consolo (@radchickyo) August 3, 2021
Officials have warned locals and tourists to stay away from affected beaches, while local fishermen have seen their livelihoods grind to a halt.
Karenia brevis has impacted Gulf waters since at least the 1800s, typically in the autumn and winter, after Florida’s rainy season. However, the frequency and duration of recorded red tide blooms have been increasing since 1995, according to data from the Florida Fish and Wildlife Conservation Commission.
A bloom in 2018 prompted Florida Governor Ron DeSantis to declare a state of emergency, but locals say this year’s is even worse, thanks to manmade pollution and favourable conditions in which the algae can thrive. This year, more than three times the number of fish have been killed by red tide in the Tampa Bay area than in 2018.
‘Human sources of pollution supercharge the blooms’
Maya Burke is the assistant director of the Tampa Bay Estuary Program, an association working to restore and protect the waters of Tampa Bay. She says that such a severe red tide within Tampa Bay hasn’t been seen in decades.
I’ve lived in Florida my entire life, and it’s very common for us to experience a red tide in the Gulf of Mexico – it happens fairly frequently. And we’ve had several large red tide blooms in my life. What’s different about this event is what happened in Tampa Bay, it’s a really localised effect. For it to be at such a level where it's killing marine life and causing those respiratory irritations in Tampa Bay as early as the month of May and June, I've never seen anything like that in my life.
Karenia brevis is just part of the ecosystem of the Gulf of Mexico, these blooms have been documented hundreds of years before really intense human development on the coast. But when they interact with human sources of pollution, that’s what can sort of supercharge the blooms and provide all this fuel for intense and more frequent red tide. That’s what happened this year.
In March and April, 237 million gallons of toxic wastewater from a former fertiliser processing plant, high in levels of phosphorus and nitrogen, leaked or were pumped out of the Piney Point Reservoir into local waterways and Tampa Bay. Officials evacuated nearby residents and deployed emergency workers to control and repair the spill.
Officials said the water did not contain radioactive substances and would not pose a concern to marine ecosystems, but Burke and other local researchers say this influx of nitrogen into the bay would have direct impacts on red tide blooms.
[The Piney Point discharge] basically doubled the nitrogen flow to that part of the bay. It was an entire year’s worth of nitrogen delivered over a 10-day period. Karenia brevis is not a picky eater, it can consume nutrients from a variety of sources. We think that’s really what caused this bloom to intensify and take off in Tampa Bay in ways that it has never done before in my lifetime.
Warmer waters brought on by climate change can also make conditions more hospitable for these dangerous algae blooms, but the main driver is human development, Burke says, particularly pollution from wastewater and auto emissions. She worries that sustained and repeated red tide blooms will have significant impacts on local ecosystems.
Usually, the fish populations are able to rebound in about three years or so, but we are just coming out of a really significant red tide event in the Gulf of Mexico from around 2018. So things like fisheries were really just starting to open back up, and then we get hit with another event. We really worry about the long-term sustainability of our fish population. But the other thing that we worry about is seagrass [...], which performs a lot of ecosystem services that are really important to the bay, it’s a really important food source for things like turtles and manatees.
The number one thing we can do is control nutrient pollution, no matter the source. By improving water quality, you’re reducing the food that’s available to fuel these kinds of blooms in the future.
As of August 7, the bloom began to subside in the Tampa Bay area, but it continues to impact beaches in Sarasota and Manatee counties.
Several conservation groups in Florida have filed a lawsuit against Governor Ron DeSantis and regulatory agencies for the toxic wastewater spill at Piney Point. Although state and local funds have been allocated for coastal cleanups and red tide research, local associations and environmentalists have denounced DeSantis’s response to the events, imploring him to declare a state of emergency.