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How hurricanes can impact red tides

Sometimes a hurricane can end a red tide. Other times? Not so much.

Red tide season usually lasts from October to around February, but the current red tide has stayed along the coast for around 10 months, killing massive amounts of fish as well as sea turtles, manatees and a whale shark swimming in the area. Photo by Joe Raedle/Getty Images
Red tide season usually lasts from October to around February, but the current red tide has stayed along the coast for around 10 months, killing massive amounts of fish as well as sea turtles, manatees and a whale shark swimming in the area. Photo by Joe Raedle/Getty Images

JACKSONVILLE, Fla. – Red tides result in smelly fish kills that often show up in the summer through fall and can be especially irritating for people near affected areas.

When hurricanes churn with red tide, outcomes can be mixed sometimes exacerbating red tide or ending it altogether.

In 2005, Hurricane Katrina ended what could be one of the worst red tides similar to the massive fish kill recently seen along the Gulf in 2018.

The hurricane-driven winds pushed Gulf currents in a way that reduced the tiny organisms that poison marine life and cause respiratory illness in humans.

But it doesn’t always work out for the better.

Gradients between salty and less saline lighter water can concentrate red tide when hurricanes dump rain.

While some oceanographers suspect rain runoff laden with pollution or sewage may boost red tides, there is agreement that nutrients play a significant role in generating red tide outbreaks.

The Gulf of Mexico in general lacks nutrients closer to the coast. They are locked in the deep, blocked by a barrier of shallow seafloor along the west Florida coast called the continental shelf.

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Red tide thrives offshore under the low nutrient conditions generally found in the middle of the continental shelf.

Red tides are suppressed when deeper ocean currents push nutrients toward shore in spring to summer months, where fast growing microscopic plants can prevail over the slower growing red tide organisms.

Dr. Bob Weisberg, from the University of South Florida has found the loop current comes into play in forecasting seasonal red tide events.

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. (Credit: R. Weisberg, University of South Florida)

Occasionally red tide starting in the Gulf can reach the east coast of Florida. In 2017, the bloom never dissipated so that it enhanced the following year’s red tide.

By the time the red tide was near Tampa and Sarasota in high concentrations, strong easterly winds pushed the cells offshore past the dry Tortugas into the Florida Current and up the east coast.


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