NEW: Red tide is on a killing spree in Florida

Scientists are trying to solve a biological murder mystery on Florida’s southwest coast as a red tide infection endures well past its typical expiration date leaving a trail of gory evidence.

There’s little question thousands of dead fish that fouled Lee County beaches during the weekend and dozens of manatee corpses recovered since the start of the year were victims of red tide, which produces a toxin that attacks the nervous system.

But algal bloom experts are scratching their heads over why the deadly menace is still here this deep into summer.

The late checkout of Karenia brevis, which is usually gone by early spring, means it’s overlapping with a blight of blue-green algae on the Caloosahatchee River.

The combination is a gut punch to summer tourism.

“Right now, if you go out in the bay, you don’t see any dead fish because I don’t think there are any fish left in the bay to kill,” said Craig Hickok, owner of Island Jet Ski Tours in Englewood. “It used to be like an aquarium at my marina, and I look around now and there’s nothing. No life. It’s awful.”

RELATED: What killed this baby manatee? Manatee mortality highest since 2013

South Florida’s water woes come as researchers in their annual State of the Climate report released Wednesday warn that a warming globe could lead to an increase in ecological tragedies.


The years 2014 through 2017 were the four warmest years on record for Earth since measurements began in the late 1800s, according to the report.

“I find it stunning actually to see the extent of how these record warm temperatures affect very important parts of our ecosystem,” said Greg Johnson, a NOAA oceanographer who co-presented the report.

Johnson was speaking about an unprecedented three-year global coral bleaching event, but scientists, including Florida Atlantic University’s J. William Louda, have said algae blooms will worsen with the warmer temperatures and higher rainfall that come with climate change.

Record May rains in Florida are largely to blame for the blue-green algae that grew this summer in the Caloosahatchee River and St. Lucie Estuary as high amounts of nutrients were washed in from the watershed. Discharges from Lake Okeechobee exacerbate the problem, adding algae and diluting the brackish waterways.

RELATED: Sargassum assaults South Florida

But Richard Stumpf, a scientist with the National Centers for Coastal Ocean Science, isn’t ready to pin the red tide on rain.

Red tide grows far offshore in the Gulf of Mexico and can pile up near the coast in the fall as winter wind patterns blow cold fronts into Florida. It prefers ocean water, unlike freshwater blue-green algae, and is usually gone by the end of March, Stumpf said.

“We don’t understand the biology of what’s happening,” Stumpf said about the lingering red tide. “It wasn’t replaced by something else, it didn’t die off, we don’t know why that is.”

It’s not unprecedented though. A red tide bloom that began in 2004 lasted for 18 months, said Tracy Fanara, a staff scientist at Mote Marine Laboratory in Sarasota.


And while red tide will take advantage of high nutrient levels near the coast to multiply, Fanara said it’s not Lake Okeechobee discharges that initiated this year’s bloom. Also, the mouth of the Caloosahatchee is too far south for its water to reach areas such as Venice, which has also suffered bouts of red tide this summer, Fanara said.

“That’s the biggest misconception that we hear. Lake O releases did not initiate this bloom,” she said. “It is unique that it has lasted this late into the summer, but it’s not necessarily widespread and we’ve had blooms that have gone all the way up into the Panhandle.”

RELATED: Lake O discharges reduced; algae issue heats up in D.C.

Red tide can cause respiratory problems, scratchy throats, teary eyes and skin irritations if a person swims in it.

Stumpf said the red tide drifted south, then back north this summer. A wind shift is likely what caused the thousands of dead fish to wash ashore on normally pristine Sanibel Island this past weekend. The city is issuing a daily “fish kill clean-up” report because of the “unprecedented volume of dead sea life currently washing up.”

Social media is circulating heartbreaking photos of dead manatees tied to docks in Cape Coral so the carcasses don’t float away before Florida Fish and Wildlife officers can pick them up.

This year, 485 manatees have died in Florida through July 20. Of those, 29 were red-tide related with another 51 suspected to be from red tide.

The 485 is the highest number of manatee deaths for this time of year since 2013 when 694 manatees died through mid-July.

Turtles are also suffering. The number of dead or sick sea turtles in Sarasota, Charlotte, Lee and Collier counties totals 404 from Nov. 1 when the red tide event began to Monday. That’s double the amount of the five-year average, said FWC spokeswoman Michelle Kerr.

Red tide can get caught in the loop current and carried into the Atlantic where it typically disperses. That’s why it’s rare for southeast Florida to get red tide outbreaks, but it has been seen as far north as Delaware.

“It’s important for people to know that while the bloom is extending from Sarasota to Naples, it’s very patchy,” Stumpf said. “One beach may be bad and just a little down the road the other will be OK.”

People can check beach conditions, including whether dead fish are present, at The site is run by Mote Marine Laboratory.

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