ST. PETERSBURG — Carmen Hanson has spent the past four years rehabilitating abused and neglected horses by taking them to the beach.

Her business, C Ponies, used the horses to take tour groups splashing through the waters of Tampa Bay with the Sunshine Skyway Bridge in the background. The exercise is good for the horses, she said, and it shows them that not all humans are bad.

But now her work may be coming to an end.

The Pinellas County Commission on Tuesday voted 5-1 to approve an ordinance prohibiting horseback riding, walking and training in the waters of the bay within the county’s borders. It also prohibits unpermitted seagrass damage in the county’s 41 aquatic preserves.

Officials feared horse manure had a negative impact on the waters of Tampa Bay and the Pinellas shoreline.

‘We are a very pristine county, very very fragile," County Commissioner Janet Long said at the meeting. "We only have one body of water to protect. We only have one planet to save.”

But Hanson said that could spell the end of her business, because many of her rides take place on the St. Petersburg side of the bridge, at North Skyway Bridge Park. Now she doesn’t know how many of her rescue horses she can take care of without the income.

“Our livelihood was at stake," Hanson said. “They’re hitting a small business that hires minorities, they’re hitting me right in the belt.”

Tour operators such C Ponies take guests on a horseback swim along the beach near the Sunshine Skyway Bridge in St. Petersburg. But Pinellas County has banned the practice, fearing the horses and horse manure was having a negative impact on the water and sea grass beds. [ LUIS SANTANA | Times ]

Two tour companies, C Ponies and Cypress Breeze Farm, said they’ll be hit hard. Each offers $150 hour-long rides in the shallow waters of the bay. The tour groups were among the most popular activities on St. Pete’s TripAdvisor page.

But then 18 months ago, complaints started trickling in. Environmental activists feared the impact of the horses defecating in Tampa Bay, Florida’s largest estuary.

RELATED: People love riding horses in Tampa Bay waters. But what about all the poop?

Bringing horses into the bay violated county water quality ordinances, said Kelli Hammer Levy, an environmental management director of Pinellas County’s Natural Resources Division.

For one thing, there was all the horse poop. Both companies required employees to scoop manure into muck buckets. But it was impossible to collect all of the droppings while horses swam through the water.

Pinellas County has banned horseback riding along the shores of Tampa Bay to keep horse manure from affecting the health and quality of the the bay. [ LUIS, SANTANA | Tampa Bay Times ]

State officials collected water samples in areas the horses frequent that showed high levels of bacteria in the water, Levy said during Tuesday’s meeting. They found enterococci, bacteria that has been linked to infections and gastrointestinal diseases.

Pinellas officials also collected manure samples to confirm suspicions that it was the horses’ excrement that was flooding the water with bacteria and nitrogen.

“Every time horseback riding was going on," Levy said, "the water was not clean.”

Officials also want to protect the bay’s sea grass beds, which plays a crucial role in filtering water in the estuary’s ecosystem. Environmentalists worried that the horses were also ripping out the delicate plants as they trotted along the shore.

The Agency on Bay Management has spent decades restoring the seagrass population to what it was in the 1950s, said Wren Krahl, deputy executive director of the Tampa Bay Regional Planning Council, back in June. Sea grasses beds are an indicator of the health and water quality of the bay, providing food and shelter for fish and other marine species.

The new ordinance also applies to other activities that could damage sea grass, such as kiteboarding.

Levy showed the commissioners aerial images of North Skyway Bridge Park to demonstrate how the horses have changed the area.

Aerial images show changes to the sea grass beds that officials blame on horseback riding along the shore. [ Courtesy of Kelli Hammer Levy. ]

Cypress Breeze Farm owner Monika Bruehsel criticized the overhead photos, saying her business operates on a sandbar away from sea grass beds.

“You can’t actually see what kind of muck is down there,” she told commissioners on Tuesday.

More than 20 people commented during the public hearing, including one woman from Kalamazoo, Mich. Jenny Cook, a Michigan Equine Trails Committee representative, told commissioners she had organized three family vacations to Florida to go riding with C Ponies.

“It is a dream come true,” she said. "It is therapy. It is so important.”

Only one commissioner, Kathleen Peters, voted against the ordinance. She told the meeting that she took one of the horse tours along the beach to see what it was like firsthand.

“I saw an enormous amount of sea grass that we swam over and were not stepping on," she said. “The beach was pristine."

Peters also said she’s seen dogs defecating on other beaches. Should the county address that as well?

“Are we going to start patrolling every single sand bar?" she said. “It’s silly.”

The Pinellas County Attorney’s Office filed the ordinance with the state Wednesday. Signs will be installed along the Skyway causeway to spread awareness before local law enforcement starts to enforce the new rule.

As for the local businesses?

“We are going to work with the community and see if we can find some alternatives that work," Levy said. “They’re beautiful horses."

Hanson isn’t going to try to fight in Pinellas anymore. C Ponies will continue rides at its Myakka City farm. But Hanson knows that alone may not be enough to support all of her rescue animals.

“We’re going to focus on being positive and see if we can find another line of work for these horses," she said.