Toxic Algae: Florida’s Manatees in Crisis

A manatee swimming warm shallow water photo by Flickr, ASCOM Prefeitura de...

A manatee swimming warm shallow water
photo by Flickr, ASCOM Prefeitura de…

While “red tide” may sound like a biblical catastrophe, it is simply an unusual bloom of a common alga—karenia brevis—that turns saltwater a rust color.  While not supernatural this algae is not harmless, as it includes a neurotoxin called brevetoxin. In humans brevetoxin can cause muscle pains, headaches, impaired coordination, and is even occasionally fatal.

In manatees the effect is even worse, and has claimed the lives of 276 of the mammals near Florida this year alone. As the algae settles on the manatee’s food sources like sea grass, it finds its way into their regular diet. The resulting poison hampers their coordination, and leaves many manatees drowning, unable to surface for another breath. There also is evidence to suggest these blooms feed on nutrient pollution, and may be increasingly toxic due to climate change. All of this is just part of a tragic picture for manatees, as this is just one cause in the deaths of a record-breaking 769 manatees in 2013. That’s 15 percent of North America’s manatees!

A Murder Mystery?

In another part of Florida, a separate crisis within the Indian River Lagoon a crisis continues to unfold, with more than a 112 manatees dying without apparent cause since July 2012.

Manatees need to surface regularly for fresh air. Photo by USFWS SW, Flickr

Manatees need to surface regularly for fresh air. Photo by USFWS SW, Flickr

Whereas red tide may have poisoned the manatees’ diet, a separate brown algal bloom in 2011 simply destroyed more than 47,000 acres of sea grass. In its place a large amount of seaweed has grown up, which the manatees have been forced to turn to as an alternate source of food. This forced shift in their diet may have played a role in the deaths of these manatees, but owing to Florida Governor Rick Scott’s recent budget cuts, it is difficult for scientists to fully investigate the lagoon’s deadly secret.

A Larger Problem

Together with the tragically growing number of stillborn and underweight calves this year, and the manatees of Florida are clearly in crisis. Our first step to averting further tragedy may start simply with understanding. Supporting more research into the Lagoon’s crisis could help us better understand how we may address it. Most important of all is simply ensuring that the waters the manatees swim in and the sea grass they eat is not stained with toxins. Before this year there were roughly 5,000 manatees near Florida, the result of years of careful conservation efforts. Now all of this work is being thrown into jeopardy.

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