Florida manatee deaths soar as toxic algae blooms and pollution choke off their food source

Manatee – Courtesy: Shutterstock — Jacob Loyacano

Nearly 1,000 of Florida’s beloved manatees have died since the start of the year, mostly due to starvation, wildlife officials stated. 

According to mortality statistics provided by the Florida Fish and Wildlife Conservation Commission (FWC), the 984 manatee deaths recorded so far in 2021 more than doubles last year’s total of 483 deaths. 

Most mortalities were associated with starvation due to the lack of seagrasses near warm-water refuge sites in the Indian River Lagoon, the FWC said, noting that a comprehensive investigation into the deaths will continue.

Manatees, nicknamed “sea cows,” typically weigh around 1,000 pounds and are usually spotted swimming through the shallow, warm waters off Florida’s coast.

But when nutrients from runoff or wastewater containing fertilizers, microplastics, or toxic chemicals make their way into a manatee’s marine habitat — whether saltwater or freshwater — they can throw off the water’s natural balance and cause harmful algae blooms to form.

The blooms blanket the water’s surface and shade out the seagrasses beneath that rely on the sun’s rays to survive, eventually killing the grasses.

The seagrasses that survive the aggressive blooms are overgrazed by manatees whose food sources have shrunk, so the plants cannot regrow quickly enough to feed the sea cows, stated Michael Walsh, a clinical associate professor at the University of Veterinary Medicine who specializes in aquatic animal health.

Manatees begin to eat less or eat other plants that do not provide the same nutritional value they need when seagrasses die. Over time, this leads to malnutrition, and eventually, starvation. 

Manatees can travel hundreds of miles until they find warm water and a new source of food, but the colder it gets, the more food they need to survive and stay warm. If there is less food, they will succumb faster due to cold stress. For their impressive girth and thick skin, they don’t have enough blubber to keep them warm when the water temperature drops below 68 degrees Fahrenheit.

The last comparable unusual mortality rate event occurred in 2010, when Florida’s temperatures fell to a historic low in a cold snap that proved dangerous for manatees and sea life. According to the FWC, more than 760 manatees died that year.

“We are committed to working with partners and our dedicated funding to identify actions necessary to conserve Florida’s population of manatees,” Carly Jones with FWC stated. “We will continue to evaluate next steps based on what we learn from this event.”

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