The first startling photos of a recently discovered Amazon coral reef have been released, showing what scientists say may be a unique marine biome.

The race to document the mysterious ecosystem is in high gear as oil companies, which obtained drilling rights before the discovery, prepare to scout the area for future production.

Greenpeace Fish peers out from shelter in the Amazon Reef as scientists snap its photo from a submersible off the coast of Brazil.

The surprise discovery of the reef off the mouth of the Amazon River was announced by scientists in April. The ecosystem is an unusual mix of sediment-heavy freshwater from the river plume and seawater from the Atlantic in a subtropical region. Much of the reef is in deep (up to 400 feet beneath the surface) or in murky water, which significantly reduces sunlight reaching the reef.

“We found a reef where the textbooks said there shouldn’t be one,” Fabiano Thompson of the Federal University of Rio de Janeiro, a co-author of the report revealing the reef discovery, told National Geographic last spring.

The reef extends almost 620 miles along the coast of Brazil and covers some 3,600 square miles with corals, sponges and red algae. It reaches from the Brazilian state of Maranhao all the way to French Guyana.

Greenpeace Researchers capture the colors of the Amazon reef on film for the first time.

Greenpeace Light infuses the waters of the Amazon Reef far below the surface.

Greenpeace Scientists are already worried about the threat of oil drilling near the reef.

The latest addition to the world’s list of reefs is already in trouble. The mouth of the Amazon is about to be a focus of oil exploration. The oil giants Total and BP plan to begin exploratory drilling in the area, according to Greenpeace.

Total has oil rights to territory less than five miles from the reef. Researchers worry that drilling disruptions or an oil spill could be catastrophic. The area also provides crucial habitat for the vulnerable American manatee, the yellow-spotted Amazon river turtle and giant river otter.

Greenpeace Scientists believe the surprise Amazon coral reef could be a new marine biome.

Greenpeace A reef resident is watched by scientists from a submersible research station.

Oceanographers who discovered the reef are currently onboard the Greenpeace ship MY Esperanza, on an expedition to document the reef.

“This reef system is important for many reasons, including the fact that it has unique characteristics regarding use and availability of light, and physicochemical water conditions,” Nils Asp, researcher at the Federal University of Pará in Brazil, said in a statement to Greenpeace. “It has a huge potential for new species, and it is also important for the economic well-being of fishing communities along the Amazonian Coastal Zone.

“Our team wants to have a better understanding of how this ecosystem works, including important questions like its photosynthesis mechanisms with very limited light,” Asp continued. “Hopefully, this will lead to a gradual mapping of the reef system.” Less than 5 percent of the reef system has been mapped.

In the current Greenpeace expedition, pairs of researchers from the University of Rio are diving in a minisub to observe the reef and take photos.

Greenpeace Researchers Fabiano Thompson and Kenneth Jozeph Lowick prepare to descend from the deck of the Greenpeace ship MY Esperanza to explore a new coral reef discovered off the mouth of the Amazon.

Greenpeace Oceanographers take off in submarine launched from Greenpeace ship MY Experanza off the coast of Brazil to explore the Amazon Reef.

Greenpeace Researchers Ronaldo Francini Filho and John Hocevar descend in a mini-submarine for their first close-up examination of the Amazon Reef.