Recent cold fronts were good news for Tampa Bay’s red tide situation. At least for now.

ST. PETERSBURG — Under Karen Henschen’s microscope, a single drop of ocean water comes to life.

Popcorn-colored cells float around like butterflies. They dart, then pause, then dart again. An entire world teems with motion in an amount of water that would barely cover the face of a penny.

“What we’re looking at here are Karenia brevis cells, which are what cause Florida’s red tide,” said Henschen, a research associate at the Fish and Wildlife Research Institute in St. Petersburg. “They’re beautiful, they’re healthy and they’re eating well. In short, they’re surviving.”

That may be good news for the algae species, but not for humans.

This particular water sample was collected less than 24 hours earlier offshore of Anna Maria Island, near the mouth of Tampa Bay. Henschen’s analysis, completed Wednesday morning, shows red tide conditions are improving — but yes, still lingering — across the bay area.

There were between 1,000 and 10,000 Karenia brevis cells per 1 liter of ocean water in Henschen’s latest tests from Anna Maria Island, or a “very low” amount relative to the most severe red tide blooms. At the current level, there’s a chance for respiratory irritation and potential for shellfish harvesting closures, according to the state agency.

“The blooms have definitely shifted south again, but there’s still red tide around,” said Kate Hubbard, the director of the state’s Center for Red Tide Research. The recent cold fronts have brought southward winds that push the toxic algae away from Tampa Bay and toward Sarasota. Blooms have ebbed and flowed offshore of Southwest Florida since Hurricane Ian’s landfall in late September.

“It’s still something that we’re keeping a close eye on, but we’re not seeing those same high concentrations here” compared to what was documented in Pinellas County in December, she said.

Below: The latest red tide water samples from the Florida Fish and Wildlife Conservation Commission.

As with all toxic algal blooms, conditions can change quickly based on weather, ocean currents and other factors. But the snapshot of the current conditions offshore of Tampa Bay — compared to the bloom’s peak last month — is a hopeful sign that things could be trending in the right direction. At least for now.

Of the 89 samples in which Karenia brevis was detected in Southwest Florida over the past week, 11 were considered “blooms,” or more than 100,000 cells per liter of water. None of those blooms were documented in Pinellas County, compared to nearly 20 measurements over the span of one week there last month. Instead, red tide is now lingering offshore of Manatee, Charlotte, Sarasota and Lee counties, according to the latest Florida Fish and Wildlife Conservation Commission data.

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No fish kills were reported in Pinellas County over the past week, and there were no reports of respiratory irritation caused by the toxic algal blooms, according to the wildlife commission.

“Conditions can vary from beach to beach. We could see a bloom in one part of Pinellas County, for instance, and it could be clear in another part,” Hubbard said. Water samplers, for example, detected medium red tide concentrations at the Skyway Fishing Pier on Tuesday, state data shows. But beaches farther north that had high levels of the toxic algae last month, such as Treasure Island, are now clear.

Colder air recently is partly to thank.

Cold fronts bring dense air from the north to the south. The strong northerly winds tend to dissipate red tides and “push” red tides southwest, away from the coast, according to Chuanmin Hu, a professor of optical oceanography at the University of South Florida.

“The red tide situation has continued to improve over the past week for the Tampa Bay region, especially after this weekend’s cold front,” Hu wrote in an email to the Tampa Bay Times. “The situation is likely to continue to improve in the coming weeks.”

Pinellas County’s environmental management team was on the water recently to measure red tide levels and detected very low concentrations at two locations near Fort De Soto Park. But beyond that, most of the coastline along Pinellas County looks fairly clear, according to county spokesperson Tony Fabrizio.

“At the moment, it looks pretty good,” he said.

How to stay safe near the water

When red tide blooms become particularly severe, these are some important health tips to keep in mind:

• Beachgoers should avoid swimming around dead fish.
• Those with chronic respiratory problems should be particularly careful and consider staying away from places with a red tide bloom.
• People should not harvest or eat mollusks or distressed and dead fish from the area. Fillets of healthy fish should be rinsed with clean water, and the guts should be thrown out.
• Pet owners should keep their animals away from the water and from dead fish.
• Residents living near the beach should close their windows and run air conditioners with proper filters.
• Visitors to the beach can wear paper masks, especially if the wind is blowing in.

Source: Florida Department of Health in Pinellas County