(WSVN) - They are an icon of Florida, but this year, they are dying in record numbers. Marine biologists are horrified at the number of manatees being found dead across the state. 7’s Kevin Ozebek has tonight’s special report, “A Dying Breed.”

They are the gentle giants that slowly graze in Florida’s waterways, and in the stretch of Biscayne Bay between the Julia Tuttle Causeway and the 79th Street Bridge, manatees were once easily spotted.

Jonathan Sidner, Miami-Dade County biologist: “This was a prime feeding ground for manatees.”

Biologist Jonathan Sidner has the job of trying to count how many manatees are in Miami-Dade County. He says, over the years, sightings in this patch of water have plummeted.

Jonathan Sidner: “We saw hundreds within a year in this area, and now we’re not seeing those numbers.”

But the bad news for the species extends well beyond this part of the bay.

It’s only May, and already the Florida Fish and Wildlife Commission has documented a record-shattering 712 manatee deaths in the state. This time last year, only 252 were found dead.

Deaths are surging in Central Florida, but manatee care experts here are on edge, too.

Julie Heyde, Miami Seaquarium: “We’re seeing emaciated animals.”

Julie Heyde helps rehabilitate manatees at the Miami Seaquarium. This is where FWC sends sick and injured manatees found in South Florida.

When a nursing mother was brought in, she was swimming on her side and barely bigger than her 8-month-old calf.

Julie Heyde: “The reason that they’re coming in this time is not necessarily because for that boat strike injury. It’s because they’re malnourished.”

Manatees are no longer spotted as often in this part of Biscayne Bay because they struggle to find food here, and the root of the problem can be seen beneath the surface, at the bottom of the bay.

Pamela Sweeney, Environmental Resources Management, Miami-Dade County: “Manatees need to have the food source, and it is all of our responsibility to keep the water clean so that food source can thrive.”

Pamela Sweeney leads a Miami-Dade County team dedicated to improving the health of Biscayne Bay. That means diving in and tracking how much sea grass is growing.

Miami-Dade County employee: “We just record everything we see down there.”

This is a manatee’s favorite meal.

Galia Verona, Miami-Dade County biologist: “In this part of the bay, the health of the sea grass was considered good until recently.”

In satellite images, you can see how acres of sea grass died off right where Jonathan used to spot manatees by the dozen.

Jonathan Sidner: “They don’t have a voice, so we have to be the voice for them”

Now the goal is to get the sea grass back to get the manatees back.

As for that mother and calf at the Seaquarium, after spending weeks packing on the pounds, they have been re-released. A bit of good news in an overall sad story.

Julie Heyde: “It’s heartbreaking, for sure. We were on an upward trend for so many years that they got upgraded from endangered to a threatened species, and now their numbers are declining.”

County biologists say, when you use fertilizers and weed killers, it can eventually end up in the bay and affect sea grass, so the less you use, the better.

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