Manatees in the Florida Keys appear to have escaped the deadliest year on record for the protected marine mammal.
The Save the Manatee Club out of Maitland, north of Orlando, reported that 769 manatees have died this year as of Tuesday.
"With more than two months still to go in 2013, nearly twice the number of manatees have already died than died in all of 2012," club officials say in a report.
The previous worst-recorded rate of manatee deaths took place in 2010 when the extended period of January cold weather chilled waters where the animals usually seek warmth.
A total of 766 manatees died statewide in 2010 -- and 118 of them perished in the Keys and Florida Bay.
However, the 2013 mortality can be traced to the environmental collapse of Indian River Lagoon ecosystem, which has been linked to 224 manatee deaths in Brevard County and 40 in Volusia County.
A red tide off the state's west coast killed most of the 269 manatees that died in Lee County waters, and 31 manatees in Charlotte County.
Monroe County has suffered six manatee deaths in 2013, within the average annual range for the Keys. Three of those were attributed to watercraft strikes.
"We did not have the impact from the environmental conditions that affected the east coast and west coast," said Mary Stella, spokeswoman for the Dolphin Research Center on Grassy Key that handles manatee rescues and recoveries in the Keys.
Brian Lapointe, a researcher for the Harbor Branch Oceanographic Institute, told National Public Radio that the extensive loss of seagrass in the Indian River Lagoon has forced manatees to eat a type of red algae that has become toxic because of the lagoon's altered chemistry.
The January 2010 cold killed extensive areas of the lagoon's seagrass, and this year's release of accumulated fresh water from Lake Okeechobee after heavy rains dealt the brackish system another blow.
"There's little question that human mistreatment of the Indian River Lagoon had a hand to play in the disastrous cascade that began in 2010," said Katie Tripp, Save the Manatee's director of science and conservation. "On the southwest coast, during the peak of the red tide, manatees were dying so fast that scientists didn't have the time or resources to conduct post-mortem exams on all of them before committing them to mass graves."
The record year of manatee deaths does not correlate to the slowly increasing manatee population, Tripp said. "These deaths are not natural controls on a growing population. They are a loud and clear signal that our waterways are in trouble."