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Pinellas monitoring extensive algal bloom

Eric Horchy

Waters off of Philippe Park in Safety Harbor were cited as a fish kill zone during last year's algal bloom. The microscopic organisms are back this year.

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By Eric Horchy | The Suncoast News

Published: July 4, 2009

Updated: 08/05/2009 02:44 pm

Dinoflagellates may be tiny single-celled marine and freshwater plankton, but when in congregated masses, their impact on an array of aquatic life can be devastating.

Pinellas County officials and other area researchers are now keeping a watchful eye on Old Tampa Bay, between Safety Harbor and Weedon Island, specifically because of Pyrodinium bahamense and the algae's latest recurrence in area waters.

Though the P. bahamense bloom has been a yearly occurrence for about 20 years here, said Cindy Heil, senior research scientist at the Fish and Wildlife Research Institute in St. Petersburg, this is the largest such outbreak on record.

"The bloom does occur every year, we just haven't seen it this big," said Kelli Hammer-Levy, division manager for the Pinellas County Department of Environmental Management. "Last year it was just in the upper part of the bay, from about Safety Harbor to the Gandy (Bridge) - an area of a little over three miles long. Now it's 14 miles long, covering about four and a half times the area."

Blooms are triggered by pollutants and other excessive amounts of nutrients, notably phosphates and nitrates found in fertilizers, which wash into the water, Hammer-Levy said.

In the case of dinoflagellate blooms, once one takes hold in an area, it is virtually there for good, Heil said. In its life cycle it basically develops a cyst, or seed stage. At the bloom's conclusion, the cysts drop into the bottom sediment to grow once again the following year.

Being a single-celled organism, the P. bahamense dinoflagellate is in the same genus as another frequent visitor to the eastern Gulf of Mexico and the Suncoast, Karenia brevis, which can cause the algal bloom known as "red tide."

P. bahamense, however, does not pack the respiratory punch or other physical ailments to humans as K. brevis.

The same cannot be said for the creatures respiring beneath the surface, though. Last year's much smaller P. bahamense bloom from July to August featured reported fish kills ranging from anchovies and mullet to stingrays and blue crabs.

The reason for this lies in a body of water's concentration of dissolved oxygen and its diurnal cycle - the natural fluctuation of oxygen levels from morning, to midday, to night. During the daytime, algal blooms will carry out photosynthesis and produce oxygen, but come nightfall, the algae will reverse course and consume oxygen to respire, Heil said.

Problems come into play when the standard Florida sunshine is blocked out by cloudy, overcast and rainy days that have been strung together this past week.

"When you have a period of a couple cloudy days like this, respiration can increase relative to photosynthesis," Heil said.

Hammer-Levy said that a normal, 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 body of water becomes hypoxic at two milligrams. This is when fish kill reports start to flow in, she said.

Unfortunately, both Hammer-Levy and Heil said, there is nothing that can be actively done to fight off blooms; just monitor and wait.

Hammer-Levy and her colleagues went out and took water samples at multiple sites on Wednesday to observe the bloom's spread. The density of the bloom previously increased from 16,000 dinoflagellate cells per liter to 1 million cells per liter in early June, she said.

Because of its reach and density, Heil said, the 2009 bloom is visible from virtually any of the bridges crossing Tampa Bay. It will appear as reddish-brown patches.

Another indicator can be observed, interestingly, at night. Dinoflagellates are a bioluminescent species, meaning that if it is disturbed, it will glow, Heil said. Boat's wakes and strong winds will trigger the glow.

As of right now, there have not been any reported incidents of widespread fish deaths, Hammer-Levy said. But the Department of Environmental Management will continue to monitor the bloom's spread until it dissipates.

To report fish kills in Pinellas County, call 1-800-636-0511.

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

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