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Warm water combined with an algal bloom could be behind dead fish in Manatee County

Human activity that adds nutrients, like nitrogen and phosphorus, tends to speed up the growth of algae and diminish the availability of dissolved oxygen.

High water temperatures and an algal bloom are killing fish in an area located between Anna Maria Island and the city of Bradenton.

The Florida Fish and Wildlife Conservation Commission said they have received multiple reports of the fish kill in Palma Sola Bay.

David Tomasko of the Sarasota Bay Estuary Program says warm water holds less oxygen, and that can be lethal for fish. To make matters worse, an algal bloom in the bay is also depleting oxygen.

"If that was pure water, we wouldn't have a fish kill," he said. "But we have an algal bloom in there. That algal bloom is occurring in very warm, very salty waters. The algae is consuming oxygen at night and that is not a good sign."

Current weather conditions have created a lethal combination for local species such as flounder and blue crab. The heat and lack of significant rain has also proved to be a fertile breeding ground for a certain type of algae called Lyngbya.

"So, nutrient management makes sense for us to do," he said. "We can't cool the water, but we can make it less susceptible to having that dissolved oxygen sag."

Tomasko says nutrient management includes having residents and businesses minimize fertilizer use. Algae growth responds quickly to elevated concentrations of nitrogen.