A study in sea cow mortality for 2021 shows a disturbing picture

July 16, 2021
By Marcy Shortuse

The death toll for the first half of 2021 is greater than it was in the entirety of previous years

While natural selection does play a part in the lifespan of all species in nature, the record-breaking amount of manatee deaths in the first six months of 2021 in the state of Florida is far from being based in nature. The fact is, we have had more manatee deaths in this first half of 2021 than we had in all of 2020.

The Florida Fish and Wildlife Conservation Commission’s report through July 2 shows that 841 manatees have died since January 1 of 2021, compared to the 637 manatees killed in all of 2020. Because the average amount of annual manatee deaths for the state is 213, the FWC is calling this an “Unusual Mortality Event.”

In the first three months of 2021 alone, more than 400 manatees died. That is more than the amount of manatee deaths in all of 2015.

In May it was announced that the FWC and the Florida Wildlife Research Institute would be receiving $8 million to help save the manatees. The funding is supposed to go toward habitat restoration and restoring manatees’ access to springs, and is part of a random list of items that were accepted into the state’s budget by the Florida House of Representatives.

That $8 million will be almost 100 percent more than the manatee program’s budget usually receives, paid for by special sea cow license plats and stickers, as well as boater registration fees and private donations. The money raised is monitored by the FWC. In the 2019-20 fiscal year manatees were allotted $3.9 million.

Unfortunately, wildlife experts have openly admitted they had no idea how they would use that money to make things better, but there are a few things in the works that could help.

For instance, the reason the majority of Florida’s sea cow deaths have occurred in Brevard County, where manatees congregate in Indian River Lagoon and the surrounding tributaries in the winter months to enjoy warmer waters, is because there are 10 power plants in the northern part of the state that discharge warm water.  There is a proposal to create new warm-water areas for manatees in other areas of the state, using solar heating or gas-fired water heaters. In recent years the South Florida Water Management District built special pools in Collier County to create new warm-water manatee habitats.

It is still unknown where any portion of the $8.3 million manatee money can be used for those types of projects. It has been suggested by some that the power industry corporations could help to pay for these warm-water substitute locations, but so far there has been no clear answer as to whether or not that will happen.

Why is it that manatees crave that warmer water in colder months, when other marine mammals seem to survive a Florida winter without it? Sea cows migrate during the winter to find warmer water because they have a low metabolism and, believe it or not, have relatively little body fat: They need to constantly eat to survive, and they need to keep their body temperature regulated to survive as well.

For decades Florida manatees have migrated to the waters of Brevard County to find warmth from the power plant emissions, which means there are a whole lot of sea cows in a concentrated part of the state during the winter months. Last March it was reported by the Daytona Beach News-Journal that 46,000 acres of sea grass had died in Indian River Lagoon, one of the very favorite manatee hangouts. That’s more than half of the amount of seagrass that was there in 2009.

When the manatees can’t find sea grass to eat in those waters, they swim only a short perimeter out before returning, so they don’t freeze to death.

According to researchers, it is definitely true that a manatee would rather starve to death than freeze to death.

But not only is the seagrass gone, not only do the manatees die but so does the ecosystem that once lived within vegetation. The seagrass is used not only as protective cover for many types of fish, turtles and other marine life, it provides a nursery for shrimp, crabs, sea urchins, anemones, polychaete worms, spongers and many other life forms.

When the sea grass is gone, so are they … and so are the species of fish, birds and land mammals that feed on them.

In particular, the southern end of the Indian River Lagoon has suffered from a series of algal and phytoplankton blooms that are caused by water pollution. The pollution comes not only from insecticide, pesticide and fertilizer runoff from central Florida agricultural areas, as well as from industrial pollution, it also comes from private homeowners who over-fertilize their lawns. When you add tar and oil residue from road construction projects and human waste from failing septic tanks, you have a mucky mess. That means the normally clear water is murky, which means that the sunlight needed to nurture sea grass can’t get through the water’s murky depths.

When you combine a hungry proliferation of sea cows with those elements, as well as with the infusion of fresh water and nutrients from Lake Okeechobee water releases that occur when the lake level gets to a certain point, you can understand why the sea grass that is so vital to so many species, and to the ecosystem as a whole, is dead or dying.

There are more manatees starving to death in recent months than there were sea cow deaths due to an excessive red tide in 2013. That year there were 830 manatee deaths.

The Florida Wildlife Research Institute backs that up in a statement made this month on the FWC website. It reads, “Unprecedented manatee mortality due to starvation was documented on the Atlantic coast this past winter and spring. Most deaths occurred during the colder months, when manatees migrated to and through the Indian River  … because of the large number of manatee deaths documented in this Atlantic event, the preliminary statewide mortality number for the first half of 2021 has surpassed the previous highest annual statewide number of 830 mortalities from 2013. As temperatures warmed up and manatees on the Atlantic coast dispersed to other habitat for foraging, the numbers of malnourished carcasses and manatees in need of rescue decreased.

“The recurrence of watercraft-related mortality as the leading cause of death in manatees necropsied in the Atlantic region in June, consistent with similar observations on the Gulf coast, underscores the need for previously identified threats such as watercraft-related mortality to continue to be recognized as a concern for the population. In addition, the long-term health effects of prolonged starvation in manatees that survived the Atlantic event to this point are not yet known.”