Bad one this year...
By Melissa Gray and Joe Sutton, CNN
updated 8:20 AM EDT, Tue March 12, 2013
(CNN) -- Florida's endangered manatees have long suffered from human activity, but this year they face an especially deadly threat hidden in the waters where they swim.
An algae bloom off southwest Florida, called Florida red tide, has killed 174 manatees since January, the highest number to die from red tide in a calendar year, state wildlife officials said Monday.
Unlike other algae blooms, red tides are not caused by pollution, the wildlife service said.
"Red tides occurred in Florida long before human settlement, and severe red tides were observed in the mid-1900s before the state's coastlines were heavily developed," the commission said.