A radioactive isotope linked to water from power plant cooling canals has been found in high levels in Biscayne Bay on the Atlantic coast of South Florida, confirming suspicions that the Turkey Point nuclear plant's aging canals are leaking into the nearby national park.

According to a study released Monday by Miami-Dade County Mayor Carlos Gimenez, water sampling in December and January found tritium levels up to 215 times higher than normal in ocean water. The report does not address risks to the public or marine life, but tritium is typically monitored as a "tracer" of nuclear power plant leaks or spills.

The study comes two weeks after a Tallahassee judge ordered Florida Power & Light Co., which owns Turkey Point, and the state to clean up the nuclear plant's cooling canals after concluding that they had caused a massive underground saltwater plume to migrate west, threatening a well field that supplies drinking water to the Florida Keys. The judge also found that the state had failed to address the pollution by crafting a faulty management plan for the plant south of Miami.

This latest test, critics say, raises new questions about what they've long suspected: that canals that began running too hot and salty the summer after FPL overhauled two reactors to produce more power could also be polluting the bay.

"How much damage is that cooling canal system causing the bay is a question to be answered," said Everglades Law Center attorney Julie Dick, who had not had a chance to review the report. "There are a lot more unknowns than knowns, and it just shows how much more attention we need to be paying to that cooling canal system."

County commissioners, who have kept a close eye on the canals and objected to the state's management plan, ordered the additional monitoring of bay water last year. FPL officials declined to comment Monday.

Over the past two years, problems with the canals have worsened exponentially. After the 2013 plant expansion to increase power output by 15 percent, the canals began running dangerously high temperatures. FPL officials blamed problems on an algae bloom that worsened after the canals were temporarily shut down during the project. But when a summer drought hit in 2014, temperatures spiked. At least twice, when temperatures soared to 102 degrees, the utility was nearly forced to power down reactors.

After obtaining permission from nuclear regulators to operate the canals at 104 degrees, the hottest in the nation, FPL officials began plotting a course to fix the canals by pumping in millions of gallons of freshwater from a nearby canal as well as increasing the amount of water drawn from the Floridan aquifer.

But the growing saltwater plume triggered regulatory scrutiny. Over the past five years, the report said, cooling canal water typically has had tritium at levels 60 to more than 800 times higher than in the bay. County staff concluded the findings are "the most compelling evidence" that canal water has spread into the bay.