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Can hurricanes impact red tide blooms?

Posted at 5:20 PM, Nov 03, 2022
and last updated 2022-11-03 17:20:40-04

Three weeks after Hurricane Ian made landfall, Eric Milbrandt with the Sanibel Captive Conservation Foundation teamed up with the Florida Institute of Oceanography and Professors at Florida Gulf Coast University. The team went on a week long expedition to see if powerful storms impact whether or not a red tide bloom will occur.

“Each time a major hurricane makes landfall, the following year, there is a long lasting, severe red tide bloom,” explained Milbrandt.

Red tides are harmful algal blooms. In past years, we have seen the algae lead to respiratory irritation in people and even kill marine life. Milbrandt said that red tide typically starts in September and continues through the fall.

But, he added that the idea that hurricanes can make them worse and last longer is not just a theory. It’s happened before.

Milbrandt said after Hurricane Charley hit in 2004, a red tide bloom began in January of 2005 and lasted almost a year. And after Hurricane Irma in 2017, he said 2018 brought one of the worst blooms Florida has ever seen.

“It had a lot of impacts to marine life, sea turtles and fish, and caused devastation to the area’s economy,” he explained.

Milbrandt said that researchers have been studying blooms since the 1940s, but not necessarily how hurricanes play a role.

But a recent week long expedition that Milbrandt was a part of focused on areas the team has revisited since 2018. The group tested the water at different depths and collected samples of nutrients and phytoplankton right after Hurricane Ian made landfall.

Milbrandt explained it’s potentially the perfect cocktail for red tide, “These storms they stir up a lot of sediment, there’s a lot of nutrients that maybe were unavailable previously that are maybe now in the water column either as particulates or dissolved.”

He furthers, “And then at the same time we had a thousand year flood event for the Myakka River. All that water is going over the landscape, picking up nitrogen and phosphorous and pushing it out into the estuaries and into the coastal oceans.”

The goal of the study was to detect if a bloom would occur before it did. Milbrandt told us that on their way back north to St. Petersburg, they did detect something. It was just 15 miles off Sanibel Island.

“I threw my bucket and grabbed some water and immediately the filter clogged and that told me that there was something in the water. And when I got back to the lab, that was two days ago, I was finally able to look at that under a microscope and it was 4 million cells of Karenia brevis, and that’s the dinoflagellate that causes red tide.”

So, could Hurricane Ian have caused the next big algal bloom?

Milbrandt believes one will come in 2023.

“That’s a prediction that I don’t know if it will hold or not but in the last 20 years it has, it’s happened twice,” Milbrandt stated.

He furthered, “It’s not a huge sample size but the more that we continue to document and look at the different pieces out there we can get a better look at how these algal blooms are forming and how they are ending.”

Milbrandt said that in a year they hope to have all of their research completed, just in time to prepare for the next hurricane season.

The team is still waiting for power to be restored to continue studying samples.