Red Tide Present Along Sanibel, Captiva Shores; Alert Issued

by SC Publisher Shannen Hayes

Water conditions in the Gulf of Mexico have deteriorated since the passing of Hurricane Ian and Tropical Storm Nicole. A high concentration of red tide near the shores of Sanibel and Captiva caused respiratory irritation and dead fish to wash up on the beaches last week.

Samples taken this week by the Florida Department of Health in Lee County and the Sanibel Captiva Conservation Foundation showed medium to high levels of red tide is still in the area. The FDOH issued an alert Thursday and posted cautionary signs at Blind Pass Beach Park.

But “additional local data and on-site observations indicate fish kills and respiratory impacts may be present along the entire Sanibel shoreline,” FDOH said in a statement.

SCCF Marine Lab Director Eric Milbrandt, Ph.D., said the red tide event started after Ian, near Sarasota, when there was flow of nutrients from offshore and substantial amounts of nutrient-rich runoff from storm flooding and rainfall.

The bloom moved south from Sarasota, he explained, and grew after late-season TS Nicole, which came 43 days after the powerful hurricane and further pushed red tide ashore with its strong onshore winds. “It’s a fairly large bloom,” said Milbrandt, “extending up to 10 miles offshore and fairly close to the Sanibel peninsula…”

Red tide is very dynamic, he explained, changing everyday with location, wind direction, tide and ocean currents and other factors. It’s also opportunistic once inshore and will use nearshore nutrients to fuel its growth.

The Lake O Effect

Nutrients from Lake Okeechobee releases are also known to feed red tide. And these back-to-back storms elevated lake levels to the highest point this year – 16 feet. The U.S. Army Corps of Engineers are considering making releases to protect its ecology and lower the level before the next storm season.

“The nutrients within releases have been associated with the intensification of red tide blooms,” said Milbandt. “We want to limit those releases, even though there are other considerations, such the level of the lake.”

SCCF and Captains for Clean Water are asking the Army Corps to refrain from authorizing additional high-volume releases and maintain lake flows at the lower end of the optimal flow range. That, they say, would ensure our coastal waters do not receive excess nutrients which could further feed the red tide.

“Our position is we have time to lower the lake before the next hurricane season,” said Milbrandt. “We think waiting for releases makes sense. That is why we are advocating for lower releases now and more releases later, hopefully when there is not as much red tide.”

The Red Tide Effect

Red tide is natural occurrence in Florida, developing each year at this time. Most red tides along the Gulf Coast are caused by Karenia brevis, a type of microscopic algae found in marine and brackish water. In large concentration, it can discolor water red to brown – giving its name.

K. brevis produces toxins which can sicken or kill fish, seabirds, turtles and marine mammals. Its toxin also causes respiratory irritation, usually temporary, in humans and pets should not come into contact with dead fish or foam on the beach during a red tide event.

Blooms typically last into winter or spring, but in some cases, can endure for more than year.

“If you look back to the 1950s,” said Milbrandt, “(red tide) has been pretty much every year. Every once in a while, a bloom will last more than a year. And that happened after Hurricane Charley and Hurricane Irma. (But) we can’t predict if it will be a very long bloom.”

Cooler water in the Gulf of Mexico stems the growth of red tide. “But if it hangs around until Spring when the Gulf warms up, there could be a continuation of the bloom throughout the summer,” Milbrandt said.

The county-wide no swimming advisory remains in effect.

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