At a Glance

An'unprecedented' number of sea turtles have been found dead on Southwest Florida beaches.The red tide event is said to be the worst since 2006.Humans are at risk as well.

The worst red tide event in more than a decade has left droves of dead animals, including an "unprecedented" number of sea turtles, on Southwest Florida beaches.

According to the Fort Myers News-Press, have been collected in Lee and Collier counties over the past week. Hundreds of others may have also died from "this particularly strong red tide event."

"We took in four new sea turtles yesterday," Heather Barron, director of the veterinarian hospital at the Center for the Rehabilitation of Wildlife on Sanibel, told the newspaper. "Two very large adult male loggerheads and each were over 200 pounds and both were very consistent with red tide poisoning. We also took in a Kemp's ridleyjuvenile and it was showing signs of red tide poisoning, and we also took in a juvenile loggerhead."

Other animals that are being affected include pelicans, double-crested cormorants and mallard and mottled ducks. Experts say the wildlife found dead on the beaches or on the surface of the ocean is only a fraction of the actual toll from the red tide. Most of the dead animals sink to the bottomof the ocean.

Humans are at riskas well.

The National Weather Service issued a red tide beach hazard advisory Friday for Lee, Charlotte and Sarasota counties through Monday.

"It's definitely an advisory for people who have respiratory issues when exposed to the algal blooms," Tony Hurt, an NWS meteorologist in Ruskin, told the newspaper.

Beachgoers to the Fort Myers area, including Sanibel and Captiva islands, not only faced the dead fish and the red tide, they were kept from enjoying the beach because of rough sea and rip tides.

Meghan Temple, 33, of Lexington, Kentucky, was on vacation with her family on Sanibel Island this week. She told weather.com the time they spent at the beach was "interesting, to say the least."

"We were coughing like crazy and the smell made our noses drip," she said. "There were dead fish everywhere, and the water was rough, super rough."

Hurt noted that respiratory symptoms could linger even after people return home from the beach.

"It's not only from being in the water at the beach but people get back home and then start to experience some of the symptoms," Hurt said. These can includecoughing, an itchy throat, watery eyes and difficulty breathing.

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In June, fishing guide Chris O'Neill told the Fort Myers News-Press the red tide that began in October. It is the longeston record since 2006.

"It’s pretty bad, and it smells like massive death," O'Neill told the newspaper. "I saw a manatee and a sea turtle and six tarponsdead in one small body of water. I only had to look for a couple of hours. It wasn’t hard to find.I could see about six Goliaths laying on the beach at Boca Grande."

The bloom originated in waters off Lee Countynear Fort Myers but has expanded to include waters just south ofTampa Bay, the Florida Fish and WildlifeConservation Commission reported in June.

Although often mistakenly used interchangeably, red tides and blue-green algae blooms are very different.

are naturally occurring algae blooms caused by Karenia brevisthat form in marine water, while blue-green algae blooms are caused bycyanobacteria and form in fresh water.

According to the FWC, blue-greenoriginate fromrunoff containing human waste and fertilizers from nearby farms and neighborhoods.Nitrogen and phosphorus, as well as other nutrients in the polluted runoff, can act like fertilizer for the algae, creating large and long-lasting blooms.

Red tides, on the other hand, occur naturally and typically develop 10-40 miles offshore in Florida. The Marine Laboratory and Aquarium notes that there isbetween nutrient pollution and the frequency or severity of red tides in Florida.However, once red tides move closer to shore, they are capable of using man-made nutrients from runoff for their growth.

If ingested, water contaminated with toxic cyanobacteria can cause nausea, vomiting and, in severe cases, acute liver failure, the FWC also said.

The Centers for Disease Control sayscan result in a rash. Some research indicates a link between long-term inhalation of toxic algae fumes and neurological disorders like Parkinson’s and Lou Gehrig’s diseases.