Turkey Point's hotter and saltier cooling canals have become increasingly inhospitable to the endangered crocodiles that use the sprawling system for a nursery.
Over the last year, the number of nests counted along the banks fell precipitously, from between 20 to 25 nests over the last five years to about a half dozen this year, said U.S. Fish and Wildlife spokesman Ken Warren. The dramatic drop has prompted federal wildlife managers to take a close look at the canals, which produce a third of the nests statewide and serve as one of only four nesting grounds.
In all likelihood, federal officials will re-evaluate measures needed to protect the crocodiles, which rebounded significantly under a successful management plan operated by Florida Power & Light.
"It's a matter of concern because that area has been significant in the recovery of the species," Warren said. "Our primary concern is what can be done to lower the salinity."
The problems with the crocs are just the latest for the aging canals, which began running hotter after the utility temporarily shut the canals down to increase power output and triggered an algae bloom. An underground salt plume, pressured by the canal's heavier, saltier water, has also spread west, threatening drinking-water supplies and prompting legal action by the city of Miami, environmental groups and rock miners.
Biologists first discovered the problem with the crocs when they visited the 6,700-acre system, which acts like a massive radiator, during the spring nesting season.
"There was a change in order of magnitude at Turkey Point and nowhere else was there a similar change," said University of Florida biologist Frank Mazzotti, who monitors the Turkey Point nests along with two nesting sites in Everglades National Park and another in Key Largo.
Scientists don't know for sure that the decline in nests is caused by the saltier water, but they do know younger crocs can't tolerate such conditions.
"It's correlated in time and space," Mazzotti said. "But these things are so difficult to prove -- the actual cause -- especially when you don't have controls."
Last year, after rising temperatures repeatedly risked shutting down nuclear reactors they help cool, FPL obtained permission to run the canals hotter at 104 degrees. But as temperatures topped 100 degrees, salinity climbed to as much as three times the nearby ocean water in Biscayne Bay.
FPL hastily obtained an emergency permit to pump water from the nearby L-31 canal to freshen the canals. But the permit only allowed pumping after enough water reached Biscayne Bay, which has also been fighting increasing salinity. FPL was only able to pump water for a few weeks before the dry season kicked in. The utility renewed the permits, but this summer's drought got in the way. Since last year, FPL has added over 2 billion gallons of water, but salinity levels remain well above the bay.
FPL officials pointed out that the number of nests fluctuates over the years, although never this low.
"We do believe that canal conditions, with increasing salinity, has reduced the number of crocs spending time in the system" said spokesman Greg Brostowicz. "But these animals move in and out of the canal system regularly."
The utility said it does not believe the increase in power output is affecting the crocs, he said.
To freshen the canals, FPL hopes to install permanent wells to pull additional water from the deeper Floridan aquifer, which lies beneath the Biscayne aquifer that supplies freshwater to the region. It also plans to control the spreading plume by installing deepwater injection wells in an agreement made with Miami-Dade County earlier this month. FPL will also ask to renew temporary permits to pump from the L-31 until salinity, which is down from a high of about 90 parts per thousand to 50 to 60 parts per thousand, matches Biscayne Bay, Brostowicz said.
If the canals return to what they were, Mazzotti said there's no reason to believe the crocs won't return.
"If FPL fixes the problem -- they need to get the salinity down and the algae bloom under control -- I don't see why the crocs would not return and the nests will be back up," he said. "That should be what everyone should be focused on."