As Southwest Florida continues to see its worst algal bloom in more than a decade, swaths of dead or dying marine animals continue to wash ashore on beaches normally packed with visitors this time of year.
The Florida Fish and Wildlife Conservation Commission (FWC) has been responding to the most recently reported finding of a dead whale shark nearly 8 meters (26 feet) long. In collaboration with the National Oceanic and Atmospheric Administration (NOAA), the two agencies performed a necropsy on the young male shark. The animal’s slightly decomposed body suggests a recent death. While officials are not able to confirm at this time whether the animal died from red tide poisoning, they can confirm hundreds of other red tide deaths and injuries found in various species of fish, dolphins, manatees, turtles, and sharks.
Earlier this week, a local news outlet reported nine bottlenose dolphins found dead of suspected red tide poisoning. All were moderate to severely decomposed, which makes sampling more difficult, but investigators were able to confirm that were three males and four females. The other two have yet to be determined.
Since last month, dozens of dead or suffering endangered sea turtles have washed up along beaches, as well as a large adult female manatee exhibiting signs of red tide poisoning.
Generally speaking, algal blooms are a common, naturally occurring event that happen when microscopic algae grow rapidly in the ocean, according to the Centers for Disease Control and Prevention. Specifically, Florida’s red tide is caused by a single-celled organism known as Karenia brevis. The dinoflagellate produces toxins known as brevetoxins, which can cause gastrointestinal and neurological problems in birds, marine mammals, fish, and even humans when it is accidentally consumed or breathed in.
When humans eat shellfish affected by the dinoflagellate algae, they can develop paralytic shellfish poisoning (PSP) or respiratory issues when breathing it in. Numerous reports of respiratory irritation have been reported in the last two weeks, according to an FWC hotline.
While red tide is nothing new in Florida, the length of this one is. For the last 10 months, officials have been monitoring ocean conditions and collecting thousands of seawater samples in a search for the algal bloom’s “smoking gun”. Conclusive evidence doesn’t point to one exact cause, but officials suspect it’s a deadly combination of the ocean’s naturally occurring bloom (which normally lasts from October to April) paired with human influences, such as changing ocean conditions and agricultural runoff and pollution.
There is no sign of the red tide ending soon, and experts warn beachgoers to report anything that looks out of place, pay attention to beach advisories and closures, and to call officials to report animal deaths or strandings.