Study said no red tide this year: what went wrong, why the science is still right

MANATEE – When a local university’s study predicted that red tide wouldn’t infect our shores, a collective sigh of relief could be heard up and down the coast.

No canceled trips to the beach. No stinky dead fish. No burning eyes or hacking up a lung.

But we all know how this story ends. Like a jinx, the toxic algal bloom clutched the coasts of Pinellas down to Charlotte for three months. When we thought it was going away for good, it came back like a boomerang. Even last week, Longboat Key still had a high concentration of red tide that it just can’t shake.

So what happened?

Don’t start pointing pitchforks at the scientists just yet.

“The one constant about science is surprise,” said Robert Weisberg, a professor of physical oceanography at the University of South Florida. He studies the physics of ocean circulation.

In June, he and a team of researchers with USF’s College of Marine Science and the Florida Fish and Wildlife Conservation Commission published two studies in the Journal of Geophysical Research: Oceans.

Red tide, a phytoplankton with the scientific name Karenia brevis, is naturally occurring; we just don’t notice it until its in irritatingly high concentrations, killing marine life and affecting our well-being.

Weisberg said scientists understand that red tide slowly blooms anywhere between 25 and 50 miles off the coast. When it’s circulated on the bottom of the ocean and gets to the shore through a process called upwelling, other plants will out-compete the red tide in low enough concentrations.

There’s also naturally occurring nutrients deep in the ocean that ride the same circulation system. Lots of natural nutrients mean other plants can compete and no red tide that year, they predicted. Deficiencies in the natural nutrients brought on red tide.

By using 24 years of satellite data to look at the height of the ocean and therefore how deep it is, the researchers built a model to accurately predict when red tide would come to the west coast of Florida. Out of those 24 predictions, they were only wrong five times.

Four of the predictions said red tide would come when it actually didn’t, Weisberg said. This year was unique for a number of reasons.