What’s polluting Tampa Bay’s water? A new study maps its ‘nutrient fingerprint’

Equipped with high hopes and an arsenal of cutting-edge technology, scientists have embarked on a new quest to scope out the sources of Tampa Bay’s pollution.

Is the water at your favorite bayside park dirty from a leaky sewage pipe? An upstream farm? Your neighbor’s over-fertilized lawn?

That’s the central question driving a new, two-year study that will document the health of Tampa Bay’s water monthly.

The research, called the Nutrient Fingerprint Project, aims to pinpoint polluters, inspire more action from Florida lawmakers and combat harmful algal blooms and ecological decline that plague the bay, organizers said.

“A lot of the technology that we’ve had up to now gives us a broad picture of what the water quality problem’s sources are. But it doesn’t give us the tools that we need to really draft legal interventions that will help us address the problems,” said Jon Paul “J.P.” Brooker, director of Florida Conservation for the nonprofit Ocean Conservancy, a partner in the study.

In other words, it has been historically hard to pin down specific polluters that release excess nitrogen, a fuel for harmful algae species, into the bay.

But there’s a new tool in the toolbox now: It’s called the EXO2, and it can monitor a suite of water quality conditions in real time. At $25,000 a pop — and with the backing of public and private funds and some extra work in the lab — it’s already giving scientists a leg up in the hunt for pollution.

“Reducing nitrogen inputs, even slightly, will have significant impacts to seagrass regrowth and a reduction in harmful algal blooms,“ Brooker said from the shores of Davis Islands this week.

”We’ll be able to understand where the nitrogen is coming from — and narrowly tailor interventions that reduce the nitrogen — so that we can have those positive impacts for the bay.”

Mapping what’s in our water

Since April, scientists have collected water samples monthly from more than 20 locations along the winding Hillsborough River.

The river was selected for several reasons: It’s a main source of drinking water for Tampa; it’s a tributary that empties directly into Tampa Bay; and there’s a mix of urban and agricultural influences along the waterway that could be monitored for pollution.

All are relevant in the quest to map Tampa Bay’s nutrient fingerprint.

“It’s a historically impacted waterway, and it brings a lot of stuff into Tampa Bay,” said Kassidy Troxell, the project’s lead scientist and a biochemistry doctorate student at Florida International University.

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Troxell is looking for chemicals that can pass through the human body and enter the marine ecosystem. Then she and her team monitor how those chemicals interact with algae-fueling nitrogen.

Each chemical detected gives a different clue about the origins of Tampa Bay’s pollution, Troxell said.

Take, for instance, an artificial sweetener called sucralose.

We use sucralose all the time: In soda. Baked goods. Frozen desserts.

Sucralose is “stable,” which means it doesn’t degrade in the environment and also doesn’t get removed during the wastewater treatment process. So when scientists find it in the natural world, they know it likely came from wastewater. But where exactly? From a septic tank? A sewage leak? A wastewater plant?

When scientists can scan for more chemicals in a single sample, the picture becomes clearer.

Caffeine, for instance, could offer more clues if it’s found together with sucralose: Caffeine degrades in the environment within 30 days. It’s also removed easily by wastewater treatment plants. So when scientists detect it in the water, they can typically attribute it to a recent sewage leak.

And that helps answer the question on the specific source of an area’s pollution.

“It really gets us to a much more granular scale,” Troxell said from the bow of a boat in the middle of the Hillsborough River. “We’re now able to tease out and untangle the sources to understand what’s happening.”

From pollution to policy

Pinpointing Tampa Bay’s pollution sources is just one step on the road to preventing it. Once pollution hot spots are identified, new regulation is needed to stop it, Brooker said.

That’s why the Nutrient Fingerprint Project is a consortium of public and private organizations and universities from across the state, including the University of Florida, Florida State University and the local University of South Florida. With enough scientific and community firepower at the table, the hope is that lawmakers will take the study’s findings seriously.

“I think it’s really critical to show that there are many different diverse stakeholders who have skin in this game. It’s not just another study done by another scientific organization,” Brooker said. “This is a broad-spectrum approach with many stakeholders who all want to see the same thing: nutrient reductions for Tampa Bay, improvements to water quality, more fish in the water and more manatees.”

The multiyear project comes on the heels of several recent studies that have underscored the growing plight of Tampa Bay, Florida’s largest open-water estuary.

In February, state water managers unveiled new seagrass monitoring results that showed the bay has lost 12% of its seagrass in two years, with some areas at a historic low. A study in April showed Tampa Bay’s redfish are contaminated with drugs. And in June, researchers found that pollution from the Piney Point wastewater disaster spread much farther than previously thought.

Hillsborough Bay, the northeastern section of Tampa Bay that receives water from the Hillsborough River, lost 428 acres of seagrass between 2020 and 2022, according to state data. That’s a decline of more than half of its total seagrass in just two years.

All of these reasons underscore the urgent importance of new research, according to Justin Tramble, executive director of Tampa Bay Waterkeeper.

On Tuesday, Tramble powered his boat while Troxell dipped her 6-foot paint stick with a 3D-printed bottle holder, with bottle attached, into the waters of the Hillsborough River. Nitrogen is natural and we need it in our ecosystems, but too much of it is a bad thing.

“Clean water supports our economy and the long-term sustainability of this Tampa Bay region,” Tramble said. “That’s why you want clean water.”

Times staff writer Jack Prator contributed to this report.