Noxious Algae Bloom Returns to Tampa Bay

By Nanette O'Hara

An algae bloom is again covering a wide swath of Tampa Bay north of the Howard Frankland Bridge.

The algae, called Pyrodinium bahamense, is the same type that has flared up in Old Tampa Bay almost every year since 2007. The cysts remain dormant in the bay sediments until conditions are right for them to emerge or "bloom," usually following early hot weather and heavy rains in May or June.

The largest bloom to date occurred in 2009, when the algae gave an 11-mile stretch along the bay's eastern shoreline, from the Courtney Campbell Causeway to the Gandy Bridge, a reddish tint similar to tomato soup.

This year's bloom is occurring a little later in the summer, and scientist aren't sure why.

Sampling crews with the Environmental Protection Commission of Hillsborough County first detected the presence of the algae in July. Cell counts in early August showed concentrations at some stations as much as 16 or even 20 times the July counts.

Pyrodinium is not the type of algae responsible for Florida's infamous "Red Tides." However, it is a harmful algae that can reduce oxygen levels in the water and lead to fish kills. No fish kills have been reported yet in association with the current bloom.

Most algae, including Pyrodinium, are associated with the presence of too much nitrogen or phosphorous in a waterway. Nitrogen is the primary pollutant of concern in Tampa Bay. The bay typically receives high amounts of nitrogen in the summer when heavy rains wash fertilizer residues, vehicle exhaust, sewer overflows and other forms of nitrogen into the water.

This year's bloom appears to be even more rust-colored in appearance than previous blooms, and is readily visible to motorists on both the Courtney Campbell Causeway and the Howard Frankland Bridge.