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Harmful algae blooms are occurring on the coast of Sarasota Bay

Blue-green algae floats on the surface of a body of water. A wooden pier is in the background.
Florida Fish and Wildlife Conservation Commission
In a photo from 2010, blue-green algae blooms on the surface of the lower St. Johns River. Similar blooms are now being spotted in Sarasota Bay.

While most algae blooms are beneficial, some can be harmful. These cyanobacterial blooms can look like foam, scum or mats on the surface of water — and they come with an unpleasant odor.

If you have walked along the beaches of Sarasota and Tampa Bay recently, you might have noticed strange mats floating in the water.

These mats are known as “blue-green algae” — scientifically named Lyngbya majuscula — one of the most important oxygen-producers on Earth.

Lyngbya is a natural part of the Sarasota Bay ecosystem, with blooms that have been occurring in the spring for a couple of years. While most of the blooms are beneficial, some can be harmful. These cyanobacteria blooms can look like foam, scum or mats on the surface of water with a naturally unpleasant odor.

If a bloom lasts too long, it can decrease the oxygen in water and cause problems for wildlife ecosystems. Over half of the statewide test sites have shown excessive amounts of algae.

Sarasota Bay Estuary Program Executive Director David Tomasko said that while it's uncertain whether the algae levels are increasing, they are worse than last year.

“What we seem to have now is a combination of three things,” said Tomasko. “The water temperature is getting warmer because it’s spring, there’s enough light to penetrate the bay’s surface, and the third thing is there has to be prior nutrient load.”

What you see on the water’s surface is a reflection of nutrients, like fertilizers and other harmful runoff that washed into the bay about two months ago.

Swimming in water that has this amount of algae could be harmful. Tomasko described the feeling as coming in direct contact with fiberglass insulation.

In addition to causing the death of marine life, the toxic algae that washes onto shore has been known to be fatal to dogs and horses who have consumed it.

It has also caused problems for waterfront businesses and homes.

“It doesn’t look good, it doesn’t smell good, if your house is on the waterfront, it’s probably not going to be great for your property values, so there’s that kind of economic and aesthetic issue,” said Tomasko.

There are several actions people can take to help reduce blooms.

“If you have reclaimed water, don’t fertilize at all. Don’t blow your grass clippings into the bay and storm drains. Pick up after your dogs,” said Tomasko.

And if there is any good news, Tomasko describes the overall water quality of Sarasota Bay as being the best it has been in the last fifteen years.

Madelyn Todd is a WUSF-USF Zimmerman Rush Family Digital News intern for spring of 2024.