Winter is the deadliest season for Florida’s manatees. They respond to the cold in dramatic fashion, maybe more so than the average South Floridian. Today the endangered mammals are congregating by the thousands in warm water springs and power plants around the state seeking warm water.
Manatees exposed to cold water, below 68 degrees, for extended periods of time become susceptible to “Florida frostbite,” or white ulcerations around the face and snout. They will lose weight and eventually die.
“They just can’t handle the cold water,” said Tom Reinert, who supervises the manatee rescue and recovery program with the Florida Fish and Wildlife Conservation Commission.
Manatees have been feeling the cold spell this month. South Florida air temperatures hit lows in the 30’s last week and will do so again this week.
Last winter manatees died in record numbers. By April 9 more manatees had died in 2010 – 480 – than in all of 2009, which held the previous record for mortality with 429 deaths. Most of these deaths were due to cold stress, Reinert said.
In January, Miami, Fort Lauderdale and West Palm Beach all saw 12 consecutive days of air temperature lows below 50 degrees.
Aerial population surveys conducted immediately following this cold spell at springs and power plants resulted in a count of more than 5,000 animals, the largest number ever counted.
On the east coast three fourths of manatees surveyed were found at power plants with warm water outflows. “Manatees have become dependent on man-made sources of warm water,” Reinert said.
Power plants use water from canals for cooling purposes and discharge warm water. This mimics the protection manatees found before man at natural warm water springs.
Last week at the manatee viewing center at Tampa Electric’s Big Bend Power Station, visitors encountered over 50 animals in close proximity at the power plant’s canal. The temperature in the canal was a tolerable 70 degrees while the gulf water in Tampa Bay reached 54 degrees.
The former manatee viewing center at Florida Power and Light’s Riviera power plant was closed for security reasons but the company offers a webcam for the public. Today, over 30 animals can be counted within the frame.
What happens when power plants close down? Manatees have a strong sense of site fidelity, according to Reinert, which means that they will return to the same warm water site year after year. They will return years after the power plants have closed down.
Manatees died in big numbers in the 1990s after the closing of pulp mills in Jacksonville, said Craig Pittman, St. Petersburg Times environmental journalist and author of Manatee Insanity.
Scientists have been noticing the link between manatees and power plants since the 1950s when biologist Joe Moore studied manatees at industrial sites along the Miami River, Pittman said. They were swimming in the river despite it being “indescribably polluted” by raw sewage discharge. “We have altered their behavior,” Pittman said.
Habitat loss has also contributed to manatees becoming dependent on power plants. The depletion of Florida’s aquifers for human consumption, according to Reinert, has caused flow pressure to decrease in warm water springs, meaning fewer animals can use them.
“Kings Bay Spring’s [discharge] used to be so strong that people used to not be able to stand on top of it,” Pittman said. “It is much less powerful nowadays.”
“We’ve decreased manatee habitat but increased it by putting up power plants that put out warm water,” said Reinert.
Most of the cold stress deaths in early 2010 occurred along the Space and Treasure Coast in Brevard and Indian River counties respectively. Here, there is a large gap between power plants, the distance between Cape Canaveral and Palm Beach County. Many manatees died getting caught in between, said Reinert, causing one of his colleagues to dub the corridor the “wall of death.”
The Fish and Wildlife Conservation Commission rescues injured and distressed manatees but mostly what they do is recover manatee carcasses. They do this to determine cause of death, which ranges from watercraft injury to cold stress to red tide.
The carcasses are sent to the agency’s necropsy lab in St. Petersburg. Last winter, the lab was handling 10 carcasses a day six days a week during the cold spell, according to Reinert. Manatee carcasses were stacked in the lab’s walk-in freezer and its necropsy table. They were on the floor. Some were even waiting outside the lab.
After a necropsy, carcasses are chopped up and placed in 55 gallon drums for rendering into oils for bio-diesel. Last winter the renderer under contract with the agency could not keep up with all the carcasses, Reinert said. The renderer was picking them up twice a week and couldn’t keep up, so carcasses were dumped in landfills.
