SCCF Marine Lab scientists are tracking floating mats of cyanobacteria that have been sighted on both sides of the Sanibel Causeway since last Friday.

“These mats start out on the bottom or on top of Caulerpa or seagrass beds and float up, and some of them end up along shores or heading out the passes,” said Research Scientist Rick Bartleson, Ph.D.

He says excess nutrient loadings of nitrogen and phosphorus cause the overgrowth of cyanobacteria and macroalgae.

“The main species is Dapis pleousa, which isn’t toxic, but there could be other cyanobacteria and dinoflagellates mixed in that are toxic and which could cause contact dermatitis,” he said.

Yesterday, some mats were visible in swash zones along the causeway and near the Sanibel boat ramp.

“There were also some large mats floating, but not as many as Friday and Monday,” said Bartleson.

He says spring is a common time for the overgrowth of these mats if the estuary receives excess nutrients.

To help the Marine Lab track these mats, please report algae sightings through our Algae Reporting App.