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Old Tampa Bay algal bloom getting worse

Photo from Dorian Photography

An aerial shot of the P. bahamense algae bloom in the section of northern Old Tampa Bay around the Courtney Campbell Causeway.

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By Eric Horchy | The Suncoast News

Published: August 8, 2009

Roughly two months after the discovery of a massive algal bloom in Old Tampa Bay, conditions have continued to deteriorate and the marine plankton's density has increased nearly fourfold.

And as things seem to be getting worse before they get better, newer blooms of differing species are now being monitored in two Hillsborough County locations; Hillsborough Bay and the Palm River.

The Pyrodinium bahamense bloom, which extends from the northern reaches of the Bay to Weedon Island in the south, has been measured at 3.75 million cells per liter, said Kelli Hammer-Levy, division manager for the Pinellas County Department of Environmental Management. That is up from a reading of 1 million c/L in early June.

Although the P. bahamense species, a dinoflagellate, is a nonirritant to humans, a persistent, dense bloom in a waterway can potentially cause ecological havoc.

The reason for this lies in a body of water's dissolved oxygen concentration and its diurnal cycle, the natural fluctuation of oxygen levels from morning, to midday, to night.

During the daytime, the algae in a bloom carry out photosynthesis and produce oxygen. Come nightfall, however, the algae will reverse course and consume oxygen to respire, Cindy Heil, senior research scientist at the Fish and Wildlife Research Institute in St. Petersburg, wrote in a July article to which she contributed.

According to Hammer-Levy, a healthy level of dissolved oxygen is around 5 to 6 milligrams per liter of water. A level of 3 mg/l can begin to stress animal life, and the subsurface environ becomes hypoxic at two milligrams. This is when fish kill reports start to flow in, she said.

She said no fish kills have yet to be reported in Pinellas, and Richard Boler, an environmental scientist with the Environmental Protection Commission of Hillsborough County, dittoed the lack of such accounts in Hillsborough.

Boler, who also assists in the monitoring of Old Tampa Bay, said a few stations have recorded dissolved oxygen levels from 2 to less than 1.

To the east, another dinoflagellate, Ceratium hircus, has infested Hillsborough Bay. Chattonella subsalsa, a form of algae known as a raphidophyte, is growing within the Palm River, Boler said.

A University of Washington School of Oceanography Web site describes Chattonella as a member of "a genus that has caused immense losses to the finfish aquaculture industry worldwide," citing a 1989 outbreak in Japan that caused $157 million worth of damage to farmed yellowtail tuna.

In terms of range, Boler said, this year's algal activity is the most widespread he has seen in area waters since blue-green algae blooms of the mid-1970s and '80s.

Algal growths are a natural phenomenon, but manmade pollutants containing nutrients such as nitrates and phosphates that run or leach into waterways can greatly exacerbate the concentration of blooms, Hammer-Levy said.

Though there is virtually nothing environmental management personnel can do to combat a bloom, the recent growths have triggered a special meeting of the Tampa Bay Regional Planning Council that will be held Aug. 13.

"I think right now it will be an information exchange to figure out who knows what about what is going on and to try to figure out if there is a strategy for management opportunities," Boler said of the upcoming meeting. "Is this something we're just going to have to learn to live with? What does this mean to Tampa Bay as a resource? And how well are we doing in terms of managing it?"

Eric Horchy can be reached at 727-815-1071 or ehorchy@suncoastnews.com.

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