Manatee, Sea Lion Deaths May Be Health Warnings for Humans

Scott Norris in St. Louis, Missouri
for National Geographic News
February 28, 2006

You may think you have little in common with a sea lion, an otter, or a manatee.

But if you happen to eat seafood, own a cat, or live near the coast, the health of these ocean animals might be relevant to your own.

Marine mammals, scientists say, are often indicators of environmental problems such as disease-causing life-forms and biologically produced toxins.

Earlier this month experts presented a new picture of contaminants in the marine environment that shows some surprising health connections between land and sea.

In Florida (map), for example, scientists are finding that powerful poisons known as brevetoxins—produced by the algae responsible for so-called red tides—are more durable and spread in more ways than previously suspected.

Recent die-offs of bottlenose dolphins and endangered Florida manatees led researchers to the new discoveries, said Gregory Bossart, director of marine mammal research at the Harbor Branch Oceanographic Institution in Fort Pierce, Florida.

Manatees and Red Tides

This month Florida wildlife officials announced record manatee deaths for January—one-third more than were reported for the same month last year.

The cause of half the deaths is still unknown, but officials suspect red tide might have played a role.

Red tide algal blooms—sudden, massive growths of algae—are known to cause massive fish die-offs, and often prompt authorities to shut down beaches and shellfish beds.

These blooms are natural occurrences but have been increasing in frequency in many parts of the world. Experts suspect water pollution and rising ocean temperatures are to blame.

Bossart's group has shown that toxins produced during a red tide become airborne, forming a chemical cloud over the affected waters.

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