Toxic "Red Tide" Plagues Florida's Gulf Coast

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Red tides (Photo credit: The Online Fisheman)

Florida residents are no strangers to harmful algal blooms (HABs), or “red tides.” The natural phenomena, which occurs along the state’s Gulf Coast annually, is the result of excessive growth of microalgae Karenia Brevis. The single-celled organisms, which are only visible through a microscope, are dangerous because they release brevetoxin – a nerve toxin, that attacks the nervous systems of animals with often fatal results.

Most years, the red tides, which emerge in late summer or early fall, last just a few months and are largely noticed only due to the namesake red color they give the ocean water. However, the most recent bout of HABs has been plaguing the area since November 2017 and spread across nearly 145 miles of the coastline in southwestern Florida. The extended season has caused mounds of dead fish to wash up on the beaches all the way from Tampa to Naples. The toxin has also killed over 266 sea turtles, 68 manatees, 11 dolphins, and a young whale shark.

Dead whale shark that washed ashore on Sanibel beach on July 27, 2018 (Photo Credit: Florida Fish and Wildlife Conservation Commission)

The stench of the dead animals has kept away the thousands of locals and tourists that frequent the area’s long, sandy beaches every summer, resulting in millions of dollars in losses for local businesses. On August 22, 2018, Florida Gov. Rick Scott declared a state of emergency for the seven counties affected by the red tides, providing $3 million to help with research, cleanup, and wildlife rescue.

Unfortunately, the situation may get worse before it gets better thanks to an outbreak of microalgae Trichodesmium in the waters offshore of Manatee County. The algal bloom, sometimes referred to as “brown tides,” floats on the water’s surface sucking nitrogen from the air. In contrast, the K.brevis, live below the surface and obtain their supply of the gas from the water. Experts at the Florida Fish and Wildlife Conservation Commission (FWC) worry that if the two blooms mix, the dying Trichodesmium could become a new source of nitrogen for the K. brevis bloom extending its stay in the area.

Red tide is causing sea turtles to get stranded on the beaches (Photo Credit: Florida Fish and Wildlife Conservation Commission)

Researchers are not sure of the cause of the 10-month-long deadly bloom, the worst in more than ten years. Most believe that it is a combination of factors such as heavy rainfall, warmer ocean temperatures, unlucky wind patterns, and pollution, which has helped create the perfect conditions for the K. brevis to thrive and linger.

“There’s a lot of different things that can be involved,” said Kate Hubbard, who leads FWC’s harmful algal bloom research group. “We do know that we haven’t had the physical conditions that sometimes help with bloom termination, that help push the bloom offshore.”

Image Credit: Florida Fish and Wildlife Conservation Commission

Though not much can be done about this year’s devastating red tides, researchers are scrambling to find ways to prevent future outbreaks. Richard Pierce, senior scientist at the Mote Marine Laboratory in Sarasota, Fla, and his team have been testing a patented technology that involves treating red-algae seawater with ozone. The researcher, who likens the process to that of cleaning aquariums and swimming pools, says, ''The algae cells are very highly reactive, and if it gets around any cell or any organic matter, it immediately destroys it. So ozone is great for killing the organism, and it's also good for destroying the toxins.”

The team is also exploring the idea of introducing other algae species to the area. Possibilities include the Diatom, a microalgae that competes with the K. brevis for food, as well as a larger algae known to release chemicals that stop the growth of red tides. "Maybe you could grow these algae around the ends of canals and in small embayment areas, which would actually inhibit the red tide from going in there in the first place," says Pierce. Hopefully, scientists will come up with a feasible solution to destroy the harmful algae before it strikes again.


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  1. What causes harmful algal blooms, or red tides?
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"The extended season has caused mounds of dead fish to wash up on the beaches all the way from Tampa to Naples."

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  • BellaTuesday, September 25, 2018 at 1:27 pm
    This is so sad and scary
    • gigiTuesday, September 25, 2018 at 12:56 pm
      That is realy sad
      • Billischill123Tuesday, September 25, 2018 at 12:41 pm
        I am so sorry for those animals and humans that have to deal with that. I wish there was a way I could help but I don't live in Florida.
        • whyTuesday, September 25, 2018 at 11:58 am
          fish poor fish Jk
          • anonumasTuesday, September 25, 2018 at 5:48 am
            i hate to see this stuff in the world
            • chichimonkeyTuesday, September 25, 2018 at 5:22 am
              this is just eww and poor fishies
              • LoudybellMonday, September 24, 2018 at 1:14 pm
                Sounds like the fisheys are sad . Poor fish. 😵
                • xxdaffygamerxx
                  xxdaffygamerxxMonday, September 24, 2018 at 1:13 pm
                  That's not good :( Poor fish
                  • xxdaffygamerxx
                    xxdaffygamerxxMonday, September 24, 2018 at 1:12 pm
                    Woah that's not good.
                    • wwwwwMonday, September 24, 2018 at 1:03 pm
                      this is vary sad:( pore fish

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