The signs are scary.
"WARNING. High bacteria levels ... Swimming not recommended."
Until August, the Hillsborough County Health Department had posted them once on a South Tampa beach in four years.
Since August, they've put up the signs three times.
Health officials say they don't have a good explanation, but attribute part of it to a new testing scheme for water pollution.
Another possibility: The water could be dirtier than we thought.
Officials are testing water near beaches twice as often as they used to, and using a tougher standard for deciding how much bad bacteria is too much. More testing could mean more warnings, officials say.
The new standard is based on statistics, not new health rules. The more sampling that's done, the more reliable the data and the lower the threshold, health officials says.
Since the change, authorities are seeing a few more bad samples statewide. In Hillsborough, they're seeing a lot more.
In the past four months, 21 samples exceeded the threshold. In the same period last year, none did.
The new results expose the pollution that has been there all along, said Linda Young, a Tallahassee activist with the Clean Water Network, a group that monitors water pollution issues statewide. Under the old system, the pollution "was being masked," she said.
Don't panic yet. There isn't enough data yet to predict trends, scientists say. And there are other plausible explanations.
After a long drought, normal rainfall this year could be bringing bigger pulses of bacteria-laden runoff, said Bart Bibler, who heads water programs for the state Department of Health.
The testing changes apply to more than 300 beaches that participate in the Florida Healthy Beaches Program. Now they are tested weekly instead of every two weeks.
The reason: An additional $525,000 this year from the U.S. Environmental Protection Agency. The agency wants a more accurate picture of how much potentially harmful bacteria is flushing into offshore swimming holes.
The concern is bacteria found in the intestines of warm-blooded animals.
The excreted bacteria can flow into beach areas from runoff, sewer pipes or failing septic tanks. Wild animals spread them. So do dogs and cats.
When swimmers unwittingly ingest the bacteria, they face a bigger risk of stomach ailments such as vomiting and diarrhea. If cuts or scrapes are infected, rashes can result.
Increased testing helps officials protect the public.
"We spend millions of dollars a day to get tourists," said Patricia Bigsby, who oversees testing for the Hillsborough health department. "We need not sicken them."
Six beaches are tested in Hillsborough, including Davis Islands, Picnic Island and Cypress Point in South Tampa. Ben T. Davis Beach is also tested.
The beaches are posted with warning signs if two samples in a row, taken several days apart, exceed state and federal thresholds. The signs usually remain four to five days.
The thresholds are based on health studies that determined when the risk is too great.
Since August, authorities have posted Cypress Point twice and Picnic Island once.
Earlier this month, samples from Ben T. Davis and Picnic Island exceeded the threshold, but followup samples were okay.
(To see results, go to http://apps3.doh.state. fl.us/env/beach/ webout/default.cfm.)
Before the new testing regimen, the only beach posted in Hillsborough was the one on Davis Islands, in July 2001.
No one can pinpoint the culprits.
"Some of these things are transient," said Tim Kelly with the county health department, who tested the waters of Picnic Island Monday. "Maybe a manatee just happened to go in the channel minutes before you took a sample."
Maybe at Cypress Point, a magnet for dogs and their owners, canines are contributing.
Maybe Tampa's oft-criticized stormwater system is, too.
Despite spikes in samples, bacteria levels overall continue to be low, said Bibler with the state health department.
"It doesn't appear to be a chronic problem," he said.
Only time will tell.
_ Staff writer Ron Matus can be reached at 226-3405 or matussptimes.com.