ST. PETERSBURG —- For the first time during the current bloom, state biologists have detected higher concentrations of Red Tide algae near a Pinellas County beach.
But the dead fish that washed up recently appear to be from a bloom far offshore, Kelly Richmond of the Florida Fish and Wildlife Research Institute in St. Petersburg said Wednesday.
Meanwhile the latest prediction from the University of South Florida College of Marine Sciences, released late Wednesday, shows the bloom moving southward again. If it proves true, that would mean Pinellas County's beaches could remain unsullied by Red Tide for a while longer.
The state's fish-kill hotline recently received several calls about dead fish on Pinellas beaches, Richmond said. That prompted biologists to go take water samples at Madeira Beach, Indian Shores, Sand Key, John's Pass, Pass-A-Grille Beach, Sunset Beach and Treasure Island.
In all but one case, they found exactly what they had been finding in previous weeks: either no sign of the Red Tide algae at all, or only background to low concentrations of it, not enough to cause a problem.
But in the water just north of Madeira Beach they found something new. The concentration of algae in the water there was large enough to qualify for the "medium" classification, Richmond said.
At this point it's still not quite enough to send tourists running from the surf in a panic. But this marks the first time the algae named for a St. Petersburg-based scientist has reached that level at a Pinellas beach during the current bloom, which is the largest in a decade.
So far the bloom has not gotten bad enough to kill any fish in Pinellas.
"Extremely decomposed fish were noted at several beaches," Richmond said. "Biologists suspect the dead fish washed in from an offshore algae bloom seen during aerial monitoring" rather than coming from a bloom closer to Pinellas.
No one knows what sets off a Red Tide bloom, although scientists say climate change is likely to create the conditions for more of them to occur. Algae that float in the Gulf of Mexico all year in small quantities suddenly explode, multiplying rapidly and becoming a bloom that turns the water a rusty color.
When the bloom moves closer to shore, it can be fueled by human pollution — fertilizer-laden stormwater runoff and leaky sewer lines and septic tanks.
It also can be fueled by dust blowing across the Atlantic Ocean from the Sahara desert. The dust, when it lands in the gulf, contains iron that stimulates the growth of a type of bacteria called Trichodesmium. The bacteria produces nutrients that boost the Red Tide.
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Recent aerial surveys from Manatee to northern Charlotte counties discovered offshore blooms of Trichodesmium, suggesting the dust that blew across the Atlantic last month is helping to prolong and strengthen the Red Tide.
The current bloom began in November. For months it has slowly spread both north and south, each day inching a little further along the coast. Lee, then Charlotte, then Sarasota county beaches were hit hard. Finally, this month, it reached Anna Maria Island in Manatee County, right at the mouth of Tampa Bay.
Although there have been predictions it would soon move into Pinellas, that has not happened yet.
The bloom's toxic properties have killed thousands of fish, particularly snook and snapper, and are suspected in killing goliath grouper, a dozen dolphins and a whale shark. About 500 sea turtles and more than 100 manatees have died as well, and their deaths have been blamed on Red Tide.
The stench of the fish kills along the Southwest Florida coast, along with the Red Tide's propensity for making humans cough and wheeze, has caused a mini-boom for hotels along the Pinellas beaches.
The scientific name for Red Tide is Karenia brevis, honoring retired biologist Karen Steidinger, who spent decades studying its properties at the state's marine science lab.
Contact Craig Pittman at firstname.lastname@example.org. Follow @craigtimes.