Black algae washes up along the shores of the Caloosahatchee River

A woman living along the Caloosahatchee River said clumps of black algae have been washing ashore for days. She described it as a “foul smelling sludge” that she first noticed about 5 days ago.

“I was like, what is dead around here? I was like uh, then I walked out here and saw this. Thats when I posted it.” said Suzanne Kelly, from North Fort Myers, “I haven’t seen anything like this. We’ve had the red tide, algae, stuff like that.”

But what is it?

Dr. Barry Rosen from FGCU’s Water School said its a kind of red algae, called “Polysiphonia”.

He said it’s likely dying from a recent change in the Caloosahatchee’s salinity. The “foul smell” comes from it decaying.

“This is what we would call a nuisance bloom, rather than a toxic algal bloom.” Dr. Rosen said.

The only way it could cause a fish kill, is if it congregates in stagnant water, like a canal, where it could choke out dissolved oxygen. Other than that, he says its just a seasonal change, and much safer than Red Tide, or Blue-Green Algae.