Environmentalists are increasingly concerned about the sustainability of Florida’s waterways after the deaths of more than 600 manatees so far this year, three times the average rate.
Biologists with the Florida Fish and Wildlife Conservation (FWC) Commission first started getting concerned in December when manatees began dying in the Indian River Lagoon Area, one of the most biodiverse estuaries in the Northern Hemisphere and home to nearly one-third of the nation’s manatee population.
The following month, the agency noticed something else strange — a large portion of the manatees rescued from the Indian River Lagoon all the way down to the waters of Miami were found swimming sideways. According to Behavioral Ecologist and Senior Research Scientist Monica Ross, that usually indicates a manatee has made contact with a boat or other human-made object.
But the manatees encountered by scientists were not injured, they were emaciated.
“The number of deaths continued to rise and the number of rescues continued to rise,” said Ross. “Once it started to warm up the [Florida Fish and Wildlife Conservation Commission] started getting a lot more calls of animals that were orphaned calves. It's presumed that some of these recovered carcasses are the moms, and now the calves are still sitting at these warm water sites, waiting for mom to show back up, and they're starting to become skinny and emaciated. So they will be rescued.”
As manatee deaths and rescues continued to spike, wildlife managers dug into the reasoning behind the unusual mortalities, and a federal investigation was triggered by the National Oceanic and Atmospheric Administration (NOAA) at the end of March, with more money and resources being directed to state agencies and environmental groups involved in rescues.
Zoo Tampa is one of four manatee hospitals in the state, and by the beginning of April it was at 95 percent capacity after taking in sick and injured manatees.
As of April 2, a total of 613 manatees had died since the beginning of 2021, nearly eclipsing the 637 manatees that died in all of 2020. If the current death rate continues, the state could surpass the record of 830 manatee deaths set in 2013.
What biologists and wildlife managers have deduced is that the widespread manatee deaths have less to do with boating accidents and more to do with the worsening effects of climate change — specifically the higher frequency of algal blooms.
Ross described algal blooms as a shade covering the sun, creating a barrier between the seagrasses that manatees need to feed on and the source of light the marine plants need to grow.
“Any kind of submerged vegetation needs sunlight to survive — just like grass, or any kind of tree. When you have an algal bloom there are very tiny particles that, when there's high concentration of them, basically act like a cloud. They're shadowing what is underneath them so they aren’t able to get any light, so when you have the entire water column full of these tiny particles, then what is underneath just dies.”
The decline in seagrass habitat is what’s causing manatees to starve, and biologists say that has led the animals to gather in larger numbers around artificial warm-water sites, like power plants, without enough food for all of them to survive.
"The timing of the deaths is associated with manatees aggregating at warm-water sites, and we believe there's an interaction between large numbers of manatees at these warm-water sites and food availability," Gil McRae, director of the FWC's Fish and Wildlife Research Institute, told members of the Florida Senate Environment and Natural Resources Committee last week.
A new study has also shown that manatees have been chronically exposed to the key ingredient in pesticides like Roundup, due in large part to fertilizer runoff. The study by University of Florida scientists concluded that the chemical was found in the plasma of over half of the 105 manatees that were analyzed between 2009 and 2019. According to the study, the concentration of the herbicide has “significantly increased” in Florida manatees over the past decade.
“The situation in Florida presents a significant threat to all manatees and marine life as it is all connected,” says Jamal Allen Galves, an associate research biologist at the Clearwater Marine Aquarium Research Institute in Belize. “A majority of the threats that plagued the Florida manatees over the years have become real threats to the Anitillean manatee subspecies here in Belize.”
Scientists are hopeful that spring might bring some relief.
The warming waters of spring and summer are a time when some manatees will be able to leave the coastal waters of Florida in search of other food sources. Ross says that some Florida manatees have already been spotted as far north as Georgia.
For now, scientists are looking toward the future about how protective measures can be put in place for the gentle marine mammals, including the prospect of relocating them away from artificial warm-water sites and back into natural waterways.
The spike in manatee deaths comes as the state has been contending with a crisis related to a massive wastewater facility. Over Easter weekend, hundreds of residents in Manatee County were ordered to evacuate their homes as officials feared that a breach might occur at the 300-million gallon phosphate plant reservoir.
Engineers were moving quickly to get water out of the reservoir at a rate of about 35 million gallons a day last week, but environmental groups are worried that wastewater releases into Tampa Bay will fuel an algae bloom that could affect coastal Southwest Florida.
Patrick Rose, executive director of the Save the Manatee Club, said that this year’s manatee die-off should serve as a wake-up call for legislators about the effects of pollution in the state’s waterways.
“The manatees are again the sort of sentinel species that’s telling us something’s really broken here,” he said.
A version of this story was also published by The Hill.
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