Seventy miles off Ocean City, scientists aboard the federal research vessel Henry B. Bigelow are exploring a lush underwater landscape that until recently few would have imagined — colorful corals clinging to the rocky slopes of deep-sea canyons.

On this and other research cruises, remotely guided submersible cameras have captured scenes of bubblegum corals, sea whips and more growing in the dark, hundreds to thousands of feet below the Atlantic Ocean's surface. Other smaller patches dot the ocean floor in shallower waters closer to shore. Cold-water relatives of the showy corals found in warm tropical seas, these also harbor a rich variety of fish, sponges and other marine life.

"The deep sea is not just this barren place — there's amazing things that live down there," said Martha Nizinski, a National Marine Fisheries Service zoologist leading the Bigelow's recent exploratory cruise off the Delmarva Peninsula.

On Monday, prompted by what researchers found in recent years, a federal fisheries council is expected to move toward protecting some or all of the coral-lined canyons along the eastern edge of the continental shelf, which one environmental group calls "hidden treasures" of the Mid-Atlantic.

"These are fragile and beautiful creatures in areas that are just beginning to be explored," said Joseph Gordon, manager of ocean conservation efforts in the Northeast for the Pew Charitable Trusts.

Depending on what the Mid-Atlantic Fishery Management Council decides, he said, it could establish the largest marine habitat protected area ever in the Atlantic — a stretch of ocean bottom as big as Maryland, Delaware and Pennsylvania combined.

It's a new frontier for science and for conservation. Only in the last several years have scientists realized how many corals can be found in the many "submarine" canyons carved into the eastern edge of the continental shelf, from the Gulf of Maine to Cape Hatteras.

"Even though they're right off some of the most populated areas of the United States, most of these canyons have never been explored," other than for some oil surveys in the 1980s, said Thomas Hourigan, chief scientist for deep-sea coral research with the National Oceanic and Atmospheric Administration.

Unlike their shallow-water cousins, the deep-sea corals don't depend on sunlight, as they have no algae growing on them and supplying them food. Instead, the deep-sea corals sustain themselves by trapping tiny organisms carried along in the ocean currents.

Relatively few deep-sea corals are the stony type that build reefs. Many tend to be smaller than the warm-water corals, though some commonly known as sea fans or whips can grow larger.

"Like shallow-water corals, they appear to be hot spots of diversity," Hourigan said, with anemones and sponges growing on them and "everything from crabs to starfishes to shrimp and all kinds of little critters" crawling over and under them.

Experts thought deep-sea corals existed only in scattered patches around the world. With better submersibles and remotely operated vehicles for exploring deep underwater, scientists have learned they are much more broadly distributed, some are hundreds and even thousands of years old, and they're habitat for many fish and other marine life.

"And that's really galvanized efforts, not just in the United States but internationally, to protect these habitats," Hourigan said.

Several years ago, Congress directed federal scientists to make a concentrated search for them in U.S. waters. There have been a series of cruises to probe the depths along the Pacific, Gulf and Atlantic coasts.

The mission of the NOAA vessel Bigelow during its 12-day cruise this month is to explore some of the canyons along the Mid-Atlantic coast. Nizinski said it's too early to say what they'll find. On previous explorations of the Baltimore, Norfolk and other major canyons, she and other scientists have seen many soft gorgonian corals in "fantastic colors,'' ranging from white to shades of yellow, gold, red, pink and orange, she said.

"I have to say we are excited about every dive that we do, because we're just not sure what we're going to find," Nizinski said.

Congress also gave the councils regulating fishing off the U.S. coasts the authority to protect them. The Mid-Atlantic council is the first to use that authority to consider broad-based protection for canyons.

The council, which meets Monday in Washington, is weighing whether to limit commercial fishing either across wide swaths of ocean bottom beyond a certain depth, or in more narrowly targeted zones around individual canyons. The biggest threat to the corals appears to be bottom trawling, in which fishing vessels haul nets across the ocean floor.

"Other places in the world, areas like this have been demolished," Pew's Gordon said.

If the most protective option under consideration is adopted, he said, it could safeguard roughly 37,000 square miles of ocean bottom.