Why Are Florida’s Manatees Starting to Die Again?


An “unusual mortality event” has reared its head again in Florida’s Indian River Lagoon, claiming the lives of nine manatees since the end of May.

“They seem to be in good condition, they’re healthy, big animals, and suddenly they get an acute shock and a lot of them drown on the spot,” Martine de Wit, lead veterinarian at the Marine Mammal Pathobiology Laboratory of the Florida Fish and Wildlife Conservation Commission in St. Petersburg tells The Christian Science Monitor.

Since designating the state a “refuge and sanctuary” for manatees in 1978, Floridians have made progress in being good stewards for the gentle giants – enforcing boat-free sanctuaries and speed limits to curb death by speedboat, the manatee’s biggest killer. But pollution-driven algae blooms are taking their toll and the mammals depend on the warm water released by power plants, which might not operate in the same way for long.

Indian River, an estuary stretching along Florida’s east coast that is home to around 50 threatened and endangered species, was struck with an outbreak of algae blooms in July 2012, which correlated with the beginning of the manatee die-off that has claimed 166 of the animals so far. The die-off seemed to let up for nine months, but the latest manatee carcasses to be uncovered bear the hallmarks of the earlier phenomenon.

The algae bloom is to blame again, scientists predict – but microscopic algae don’t kill the 800 pound marine mammals directly.

“As far as cause of death, the exact mechanism isn’t known but the thought is that because of the algal blooms, you have a loss of seagrass, which is the manatee’s primary food source, and the result is that the manatees are finding another food source, macro algae, which is toxic in and of itself or has a toxic component,” explains Katie Tripp of the Save the Manatee Club in a phone interview with the Monitor.

“We need to do a better job of protecting our waterways. These algal blooms are a symptom of bad pollution management,” says Dr. Tripp.

The manatees have been recovered with little to no seagrass in their stomachs, Dr. de Wit told the Orlando Sentinel. Instead, their digestive systems were filled with seaweed.

Manatees face much bigger threats than this particular bloom, according to de Wit, first of which is watercraft collision.

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SOURCE: Christian Science Monitor, Nicole Orttung