Horse And Bird DNA Detected In Palma Sola Bay — Genetic Tests Find Sources But Not Their Contribution

New pilot genetic testing by local environmental groups detected DNA from horses and birds in Palma Sola Bay, but the study could not quantify how much each source contributes to the bay's persistently elevated fecal bacteria readings.

The Sarasota Bay Estuary Program (SBEP), in collaboration with Suncoast Waterkeeper, conducted a two-month investigation to supplement routine weekly enterococci testing. Enterococci is a fecal indicator bacteria used by the Florida Department of Health to assess recreational water safety, but it does not identify specific sources of contamination.

What the Study Found

The laboratory searched for genetic markers from four categories: humans, horses, birds and general bacteria. Testing detected genetic material from horses and birds, but the concentrations of horse DNA were below the level required to quantify a contribution. The study found no detectable human DNA during the sampling period.

"There was genetic material there, but getting to how much, and how much of an issue it is, is not within the scope of this pilot study," said Ryan Gandy, SBEP executive director, calling the work a preliminary effort.

Suncoast Waterkeeper Executive Director Abbey Tyrna said the results indicate that horses are one part of the problem but not the only one, and that birds appear to be a seasonal contributor as well.

Context And Limitations

The pilot study was targeted and limited in scope. It did not test for other possible sources such as decomposing seagrass, dog waste, manatee feces or fish excrement. The lab's focus on only four source categories means the results are not comprehensive and cannot assign precise percentages of contamination by source.

Gandy noted that horse DNA remained detectable in some samples even during a roughly one-month interval when horseback riding operators voluntarily paused rides along the Palma Sola Causeway. He said that persistence could reflect factors such as bacteria residence time in the water or the organism's ability to feed on available organic matter.

Response From Vendors And Officials

C Ponies Horseback Riding owner Carmen Hanson welcomed the findings because horse DNA was not found at quantifiable levels. Hanson said her company invested nearly $4,000 in boats and increased cleanup efforts, collecting visible waste with nets and cleaning beaches before and after rides.

Gandy acknowledged that vendors are making efforts to reduce waste loading. After the study, Suncoast Waterkeeper recommended that the City of Bradenton consider posting warning signage near the causeway and implementing a permit system for horseback riding vendors to help manage public safety and environmental impacts.

Mayor Gene Brown confirmed receipt of the recommendations and said he would meet with scientific consultants to review the findings. "Public safety is important to us," Brown said. "We're going to keep trying to evaluate the facts."

Next Steps

Officials must weigh whether to pursue a more comprehensive microbial source tracking study. Such a study could provide clearer attribution of fecal bacteria sources but would be more costly and time-consuming than the initial pilot. Meanwhile, stakeholders debate regulatory steps, signage and vendor permitting as low-cost mitigation measures.

SBEP and Suncoast Waterkeeper emphasize that the pilot study provides useful preliminary insight but is only an initial step toward understanding the complex mix of contributors to Palma Sola Bay's water quality issues.