SCCF, Sanibel Sea School: Testing finds red tide on beaches
Water samples taken by the Sanibel-Captiva Conservation Foundation’s Marine Lab scientists from Oct. 4-10 at Tarpon Road Beach and Algiers Beach showed red tide at medium concentrations, according to officials.
SCCF reported that in addition, sampling done by the Sanibel Sea School on Oct. 9 found medium concentrations at Donax Road Beach.
“It’s the first time we’ve had counts over 100,000 since November 2018,” SCCF research scientist Dr. Rick Bartleson said. “There’s a red tide bloom south of the island that is about the size of Sanibel.”
The levels are high enough for the brevetoxin from the red tide bloom to aerosolize with onshore winds and cause respiratory irritation to beach visitors and fish kills. Counts of 100,000 to 1,000,000 cells of the red tide organism Karenia brevis per liter are considered to be in the medium range of concentration.
Over the week, counts at Tarpon Road Beach ranged from 130,000 to 1 million. The count at Donax Road Beach was 580,000, while the highest count at Algiers Beach was 352,000.
Fish kills are considered possible when counts exceed 100,000. No fish kills had been seen by SCCF scientists. But, Bartleson could feel the red tide tickle in his throat as he was collecting samples.
Two weeks ago, an offshore water sample taken by Research Associate Mark Thompson alerted scientists to an offshore bloom. The highest concentration of K. brevis found was 34,000 cells per liter at a site eight miles offshore of Sanibel.
“We’ll be going offshore again in a couple weeks and I expect we’ll find higher counts,” Thompson said. “It’s trending that way right now, where we’ve gone from inshore counts from 2,000 up to 10,000, now up to 500,000 to 1 million.”
Karenia brevis produces neurotoxins, called brevetoxins, that can sicken or kill fish, seabirds, turtles and marine mammals.