World's largest deep-sea coral reef mapped 100 miles off coast of Florida. How big is it?

Three-quarters of the world's oceans are still unmapped with much detail. But as our technology improves, researchers can see more and more of what's hidden beneath the inky depths.

Such as, say, the world's biggest deep-sea coral reef sitting off the coast of Florida.

"It's essentially the largest deep-sea coral mound region in the world that's been documented so far," Derek Sowers, the Mapping Operations Manager for the Ocean Exploration Trust and lead author of the study, told USA TODAY. "It's just this amazing, huge ecosystem, sprawling across an area about three times the size of Yellowstone National Park."

A paper published by the scientific journal, Geomatics, details efforts over the last few years by the National Oceanic and Atmospheric Administration (NOAA) and its partners to explore the Blake Plateau.

Here's what you need to know.

How big is the newly discovered deep-sea coral reef?

The reef stretches from Miami to Charleston, South Carolina, about 100 miles off the southeast U.S. coastline. It is about 310.69 miles long and reaches up 68.35 miles wide at points, NOAA said, taking up about 6.4 million acres. The nearly continuous coral mound has a core area of high-density mounds up to 158 miles long and 26 miles wide.

In comparison, the state of Vermont is 6.1 million acres, according to the U.S. Forestry Service.

The coral mounds extend across much of the Blake Plateau, an area between the North American continental shelf and the deep ocean basin along the southeastern U.S. up to North Carolina.

Why didn't we know there was a massive coral reef off the coast of Florida?

The reef is also 100 miles out, at depths ranging from 65 feet down to 3,280 feet. Scientists have known since the 1960s that there was some coral in that area of the Atlantic Ocean but they had no idea how much since it was impossible to dive that far down.

"About 75% of the world's oceans are still unmapped in high resolution, and about 50% of the U.S. waters are currently unmapped," said Sowers.

How did researchers find the new coral reef?

Our technology got better.

An area nearly the size of Florida was mapped with 31 multi-beam sonars to make 3D images of the seafloor of the Blake Plateau, according to NOAA.

"The multi-beam sonars are mounted on research ships," Derek Sowers, the Mapping Operations Manager for the Ocean Exploration Trust and lead author of the study, told USA TODAY. "That's how we can map this type of habitat."

With the maps as a guide, a submersible with manned or remotely operated subs could be sent down to send live video feeds back up.

"This strategic multiyear and multi-agency effort to systematically map and characterize the stunning coral ecosystem right on the doorstep of the U.S. East Coast is a perfect example of what we can accomplish when we pool resources and focus on exploring the approximately 50% of U.S. marine waters that are still unmapped," Sowers said.

What did scientists find in the new deep-sea coral reef?

The mound region is made up of cold-water coral mounds, which are corals "shaped like bumps or pinnacles on the seafloor and can range in height from about ten feet to hundreds of feet tall, but average about 65 feet tall on the Blake Plateau," said Sowers in an email. "They are formed over long time periods out of the skeletal material of cold-water 'stony corals' and also sediments that are trapped by the coral rubble material."

According to NOAA, the largest area of the reef, which has been nicknamed "Million Mounds" by scientists, is mainly made up of stony coral or Desmophyllum pertusum. The cold-water species is mainly found in the ocean at 656 to 3,280 feet deep and survives by filter-feeding biological particles.

How is this coral reef different from Florida's Coral Reef?

Florida's Coral Reef, the only coral reef system in the continental United States and the third-largest barrier reef ecosystem in the world, is a shallow-water reef. This deep-sea one is biologically different, Sowers said, because the corals are out of reach of sunlight and in water that's on average 39 degrees Fahrenheit.

"They don't rely on photosynthesis because they're actually living in the dark," said Sowers. "But they do rely on filter-feeding particles that are coming down through the water column, and they capture those particles and bring them in."

Because it's farther down, deep-sea reefs don't have the same problem with coral bleaching, coral that turns white from stress from environmental changes such as climate change and recent record-high temperatures, leaving them susceptible to disease or starvation.

Happy Coral Reef Awareness Week! What you need to know about Florida’s Coral Reef

Deep-water reefs do still face dangers from climate change, however. "Climate change and the changing water temperatures and acidity of the ocean can also impact these reefs and is something that we need to try to manage in the future so we can keep these ecosystems functioning," said Sowers.

Deep-sea corals are still poorly understood, NOAA said, but studying them can provide insight into their health and resiliency which can help scientists predict "the impacts of human activities on coral communities" and help with "developing solid plans for their protection."

Why are coral reefs important?

Coral reefs are both beautiful and utterly vital to the ocean ecosystem and the local environment. They provide homes, food and breeding sites for millions of marine plants and animals, including the fish we eat. They offer important resources we've used to fight cancer, pain and inflammation. They help protect shorelines from extreme weather, erosion and flooding, and they provide income through fishing and tourism for millions of people, supporting over $6.3 billion in tourism revenue, according to Darren Soto, D-Kissimmee.

Coral reefs cover only a tiny area of the ocean floor — about 1% of the total marine habitat — but, like bustling cities, they provide homes and life to a wide variety of life.

"Coral reefs are among the most biologically diverse and valuable ecosystems on Earth," according to the U.S. Environmental Protection Agency. "An estimated 25 percent of all marine life, including over 4,000 species of fish, are dependent on coral reefs at some point in their life cycle. An estimated 1 billion people worldwide benefit from the many ecosystem services coral reefs provide including food, coastal protection, and income from tourism and fisheries."

And reefs help protect the coast, the first line of defense for a state that gets slammed with hurricanes and tropical storms every year. "Florida’s Coral Reef provides more than $355 million per year in flood protection benefits to buildings," the FDEP said on the floridascoralreef.org website, "and protects nearly $320 million in annual economic activity."

This article originally appeared on The Daytona Beach News-Journal: Giant coral reef off Florida is world's largest, bigger than Vermont