Is there horse poop in the bay? What testing found amid Florida water debate

Results from advanced water testing in a Southwest Florida bay traced horse DNA to bacteria found around a causeway, adding fuel to a long-standing debate that horses contaminate the waterway.

Scientists with the Sarasota Bay Estuary Program and Suncoast Waterkeeper recently began the advanced sampling to pinpoint percentages of fecal indicator bacteria sources around the Palma Sola Causeway.

The groups collected water samples from all four sides of the causeway and, in three out of four sites, horse DNA was found as a source of fecal bacteria. For the water sample collected from the southeast site, birds were also identified as a source.

While the new samples provided some insight, the results also raised more questions, and the need for more tests.

“We had hits for horses as a source for bacteria in three of the four sites, including the bathing beach site,” said Dave Tomasko, the executive director of the estuary program. “At all three sites, the level was low enough that we couldn’t actually even quantify it.”

This means that, while there was a trace of horse DNA in the bacteria, the reading was so low that scientists aren’t able to accurately estimate if the bacteria was 50% or 0.5% horse-related.

“It’s like you hear a noise in the woods, but you don’t know how loud it was…like you don’t have a decibel reading,” Tomasko said.

Suncoast Waterkeeper and the Sarasota Bay Estuary Program plan to conduct four more samples, and Suncoast Waterkeeper Executive Director Abbey Tyrna said the research could help direct municipalities for potential regulation.

Need for specific DNA source sampling

Horseback riding in Palma Sola Bay has been a long point of contention between the horse riding companies, scientists and the community.

About two years ago, Tomasko gave a presentation to the Bradenton City Council on the potential impact of horses on the City of Bradenton. Part of the presentation focused on what impact, if any, the horse fecal bacteria has on the local waterway.

Suncoast Waterkeeper conducts weekly monitoring of fecal bacteria indicators throughout Manatee and Sarasota counties. One of those sites is the north side of Palma Sola Bay, which has high levels of fecal indicator bacteria 80-90% of weeks, according to Tyrna.

The Florida Department of Health designated the south side of the causeway as a bathing beach and, because of that, the agency conducts regular testing of the southeast side.

Both the health department and Suncoast Waterkeeper’s sampling looks for the presence of enterococci bacteria.

Enterococci is one of the main fecal indicator bacteria, but Tomasko said the indicators aren’t specific enough to pinpoint a source. Sometimes higher levels could mean more decomposing vegetation, not animal feces.

“None of them are specific to humans or mammals, or even animals,” Tomasko said. “Finding high levels didn’t necessarily mean the horses were the reason. So we suggested some source identification work should be done.”

Last year, Suncoast Waterkeeper took the next step. The samples confirmed that horse DNA was found in the fecal bacteria, but the question remained about how much horse feces was contributing to the issue, which is what the latest testing is trying to do.

Were the results a surprise?

“When we found the genetic indicator of horses as a source of some of the bacteria at three of the four sites, we thought it was important enough to let our policy board members know about it,” Tomasko said.

While the estuary program and Suncoast Waterkeeper expected to find evidence of horse DNA where horses enter the water on the north side, it was alarming to find it on the opposite side of the causeway.

“We don’t want to suggest it’s terrifying to dip into the waters. Horse manure is not as problematic as coming into contact with human fecal material,” Tomasko said. “Nonetheless, we do think finding evidence of the horse-related bacteria making it across the causeway…that’s a little different than saying, ‘Don’t swim next to the horses.’”

On the day the two groups collected water samples, Suncoast Waterkeeper also conducted its routine monitoring for enterococci.

Tyrna and Tomasko noted it was interesting that, while enterococci levels were low that day, the more advanced samples still found traces of horse DNA.

But Tyrna said it didn’t surprise her that they found traces of horse DNA.

“We were wading in the water each week and moving horse manure out of the way in order to get a sample,” Tyrna said. “We knew the problem was horses.”

Horseback riding company rebuttals

Carmen Hanson owns C Ponies Horseback Riding, a company that uses Palma Sola Bay about four to five times a week for horseback riding.

She argued the coin can be flipped either way. While some may find the detection of horse DNA alarming, Hanson says the low numbers are a sign that the horseback riding companies are doing a good job of keeping the bay clean.

“For it to be tested so mildly that they can’t put a percentage on it, to me that’s good news,” Hanson said. “The testing is so minimal that they couldn’t even say it was 0.05%...it’s so minimal that obviously we’re doing our job.”

Hanson said the company has cleanup crews that start cleaning the beach before they unload the horses, picking up any trash on the beach before the horseback walks begin.

Then, the crews have horses walk along the beach line first in case the horses need to defecate before getting in the water. Once groups are in the water, other crew members follow along to clean up any feces that the horses may drop.

“We use pool nets so that we try to get 99.9% of the waste,” Hanson said.

Hanson also pointed out that, at one of the sites, bird DNA was also found in an unquantifiable amount.

Regulation possible moving forward

While horseback riding companies and scientists may not agree on how harmful horse manure is, both sides see a possibility for compromise on regulation.

“We’re not opposed to regulation. We’ve never been opposed to regulation,” Hanson said. “We’ve never been opposed to working with the city on regulating anything.”

However, Hanson added that regulating horseback riding now would be “jumping the gun.”

“I think they need to continue to do the testing. When that south side does get shut down with a no swim advisory, that’s the perfect time to test,” Hanson said.

While the the estuary program isn’t a regulatory board itself, there are regulatory stakeholders on its policy board. Tomasko said he plans to present findings to Bradenton’s city council in September.

Tyrna said Suncoast Waterkeeper has never thought horseback riding should be eliminated entirely from Palma Sola Bay. Some regulation options could mean prohibiting horses from certain areas, diapers for horses or a permitting system to limit how many groups are allowed.

Speaking to fishermen, Tyrna said she’s heard stories about how horse manure has caused bait fish to die and some have pulled up horse poop in cast nets.

Tyrna hopes the right management practices in the future could strike a balance between all stakeholders on Palma Sola Bay.

“We hope to see Palma Sola Bay be a bay where one use is not excluding another use,” Tyrna said. “Right now we have one use that is creating problems for other uses.”

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