Algae bloom ‘brown tide’ detected in portion of Sarasota Bay

[USA] An algae sometimes referred to as “brown tide” due to its tendency to turn the water a brownish color has been detected in an area of northeastern Sarasota Bay.

A water sample taken by Manatee County Parks and Natural Resources Department staff Monday and examined by the Harmful Algal Bloom group at the Fish and Wildlife Research Institute in St. Petersburg found that Peridinium quinquecorne, a dinoflagellate, was present in “bloom concentrations of over 1 million cells/L,” according to the institute’s report.

While the red tide organism, Karenia brevis, was not detected in the water, this is the first time this area of northeastern Sarasota Bay has seen a bloom of this organism since 2010.

“This information confirms what staff saw late last week (and reported over the weekend) with localized fish kills due to lowered dissolved oxygen in the water, along with the corresponding odors,” Rob Brown, the county’s environmental protection division manager, said in an email to other county officials Tuesday afternoon.

According to the Florida Fish and Wildlife Conservation Commission website, this organism can be found “year-round in many brackish and estuarine waters in Florida.”

With the bloom conditions in the water, it will “depress the dissolved oxygen in the water and create an environment where you could have fish kills,” Brown said Wednesday. “It does cause fish kill when we get to these high concentrations because of the dissolved oxygen.”

While the eastern portion of Sarasota Bay doesn’t get a lot of circulation, Brown said with the strong winds out of the north this past weekend, it could be moving around.

Late last week, residents in Paradise Bay Estates expressed concern about the large number of dead fish, foul odors and murky water. The residents in the neighborhood, 10315 Cortez Road W., said they believed it was caused by a sewage leak.

As of Wednesday, residents say that the foul odor is gone but the water is still murky.

But Manatee County officials have said it is not related to the sewage system.

The county is still in conversations with Fish and Wildlife Research Institute discussing setting up a monitoring network, Brown said Wednesday. The county sampled water at three locations Monday: Tidy Island, Cortez Kitchen Marina and Paradise Bay Marina.

“We really do need a broader survey to see the extent,” Brown said. “I am sure the algae is in other areas but maybe in lower concentrations.”

Photo: Paradise Bay Estates residents are concerned with the murky water in Sarasota Bay, which they say is killing a lot of fish.

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