Bradenton Herald
Will Florida’s red tide get worse because of Hurricane Nicole? Here’s what experts say
Max Chesnes – November 15, 2022
Red tide was found this week in the waters off Anna Maria Island, and now experts fear Hurricane Nicole could possibly make conditions worse for Tampa Bay.
Extra runoff from rainfall could mean more algal-bloom-fueling nutrients dump into the bay. That may — or may not ― spark more Red Tide.
“Of course our eyes are on any additional rainfall and runoff that might occur in response to . . . Nicole’s passage,” said Ed Sherwood, executive director of the Tampa Bay Estuary Program. “With red tide now present in lower Tampa Bay, additional nutrient loads may exacerbate the bloom if salinities remain high.”
It’s a big if, with plenty of variables. The organism that causes red tide, karenia brevis, prefers salty marine environments. Rainwater is fresh, but brings pollution along with it as it flows into the bay. That pollution, in turn, can fuel red tide blooms.
“Any additional nutrient loads to our coast — especially when a red tide is already present in the estuary — is a concern,” Sherwood wrote in an email. “As the red tide bloom that formed further south is carried by winds and currents into our estuary, any additional stormwater nutrient loads caused by (Nicole) may promote water quality declines this winter.”
State water samplers detected medium concentrations of red tide-causing karenia brevis, between 100,000 and 1,000,000 cells per liter, on the northern tip of Anna Maria Island Monday, according to the latest Florida Fish and Wildlife Conservation Commission data. Scientists consider that level a “bloom,” meaning breathing problems are possible and fish kills are probable.
On Nov. 2, small amounts were measured 11 miles offshore of Tampa Bay, data show.
There’s cause for concern for residents in the Tampa Bay area, “because it is likely that a red tide bloom will evolve here,” according to Bob Weisberg, a physical oceanographer at the University of South Florida. Once Red Tide is measured at the mouth of Tampa Bay, tidal currents could easily bring it into the estuary. Now, add the winds from Nicole into the mix.
The storm is currently pushing northerly winds, which makes conditions more favorable for the spread of red tide here, according to Weisberg. “Such winds will result in red tide cells located offshore along the bottom being transported toward the shore and hence an increase in what may be observed here in subsequent days.”
Still, the mixing of wind and water during storm events are speculated to hurt red tide, so there may also be a die-off of some karenia brevis cells, Weisberg wrote in an email. Nicole isn’t nearly as strong as the recent Hurricane Ian, though, so there’s a chance that more Red Tide organism feeds on runoff entering the bay versus being killed off in turbulent water.
“Red tide ecology is the whole shebang,” Weisberg wrote.
The most recent models from the University of South Florida’s Ocean Circulation Lab show traces of the red tide organism — resembling green strands of spaghetti on the chart — in small amounts entering into Tampa Bay over the next few days, beginning from where it was first measured on Anna Maria Island.
The takeaway is that there’s no immediate threat of dangerous red tide exposure through the weekend, but it’s definitely something to watch, according to Yonggang Liu, the lab’s director.
“It may still be OK for Tampa Bay area in the next three days,” Liu wrote in an email. “You may go to a beach and enjoy water activities without issues of red tide.”
With Nicole expected to drop as much as four inches of rain in the area, it’s still to be determined just how much runoff the bay will receive. But storm surge shouldn’t be a major issue for the estuary, according to tide models provided by Liu. Sea level will first recede, but not nearly as much as what was documented with Hurricane Ian earlier this year and Hurricane Irma in 2017.
Once Nicole passes, the bay should hopefully start to see a reprieve, according to Sherwood.
“We’re coming to the tail-end of our rainy season, so with the exception of the recent tropical storms that are impacting our region, we should start to see a decline in storm-water nutrient loads from our coast,” Sherwood said. “That in combination with cooling temperatures will hopefully lead to some water quality improvements over the next several months.”