It's taken nearly five years, 45 research expeditions, and more than 80 scientists and students, but the largest oceanic research enterprise, the ATLAS project, is officially complete.

Exploring 12 locations in the deep northern Atlantic, the project has set a gold standard for future marine research.

Driving underwater robots to areas never before explored, researchers have uncovered a dozen newly identified species, including fish, cold-water coral and other invertebrate sponge species. Not to mention the discovery of 35 known species in previously unknown areas.

Already, the results have produced 113 peer-reviewed papers, with 98 more soon to follow.

Among the new findings is a type of coral growth, known as Epizoanthus martinsae, which thrives on black corals over 400 metres deep (1,300 feet).

Other discoveries include a type of sedentary animal resembling moss, called Microporella funbio, which was found in an undersea mud volcano off the coast of Spain.

Another moss-like animal, named Antropora gemarita, was also found filtering and feeding particles of food drifting in the deep sea.

The project and its findings are unrivalled and speak to how much the deep ocean still has to offer. Yet without healthy, deep-sea ecosystems, these newly discovered species will no doubt struggle to survive.

"As the birthplace of deep-sea biology and the cradle of oceanography, the North Atlantic is the place we should know best," says Murray Roberts, the ATLAS coordinator, "but only in the last 20 years have we uncovered how varied and vulnerable its deep-sea habitats really are."

In fact, scientists today say we know more about the surface of the Moon and Mars than we do of the deep Atlantic, and that's a serious problem.

Cold water corals and seastas CREDIT IFREMERCold water corals and seastars. (French Research Institute for Exploitation of the Sea)

Sponges and corals may not seem like important animal species in the grand scheme of things, but in the deep sea they form the foundation for most ecosystems.

Marine biologists actually refer to them as the 'cities' of the deep, providing food and shelter for many more types of fish.

In a rapidly changing world, however, these remote ecosystems appear particularly vulnerable to human activity.

Despite their name, black corals are not always black, and while they do not bleach with high temperatures like shallower corals, climate change is still their biggest threat.

Given their propensity for growing in the deep, we still have very little information about these corals' conservation status, which means they could go extinct before we even find them. The same goes for any deep sea species they support.

Black coral and crabs at the ROCKALL BANK CREDIT UNIVERSITY OF EDINBURGHBlack coral and crabs (University of Edinburgh)

"If those cities are damaged by destructive human uses, those fish have nowhere to spawn and the function of those whole ecosystems is lost for future generations," Roberts told the BBC.

Oceans absorb up to a third of the carbon in our atmosphere, and research from the ATLAS project suggests half of all cold-water coral habitats are at risk from warming temperatures.

Sponge and sea urchins at the ROCKALL BANK CREDIT UNIVERSITY OF EDINBURGHSponge and sea urchins. (University of Edinburgh)

Nor is that the only threat faced by these deep sea communities. The ATLAS project found ocean acidification and fishing could also place nearly 20 percent of deep water ecosystems at high risk.

Acidification is one of the most disastrous outcomes for corals, corroding the skeleton of these reefs almost like osteoporosis in humans.

"That's attacking the very foundations of huge deep-sea coral reefs," Roberts explained to ABC News Australia.

"Predictions are showing the suitability of the habitats really collapsing over the next 100 years."

American lobster and squat lobster at Baltimore Canyon CREDIT STEVE ROSSAmerican lobster and squat lobster at Baltimore Canyon. (Steve Ross)

Even the major currents of the Atlantic are slowing with climate change, and this means the warm, salty water usually carried to the north is taking longer to cool and sink, possibly causing sea levels to rise or changing global weather patterns. It could also impact the resources deep sea ecosystems are able to access.

"Everyone knows how important it is to look after tropical rainforests and other precious habitats on land, but few realise there are just as many, if not more, special places in the ocean," says Roberts.

"In ATLAS we've studied most vulnerable ecosystems in the deep Atlantic and we now understand how important, interconnected and fragile they really are."

Lophelia pertusa CREDIT Solvin Zankl GEOMARLophelia pertusa, a cold water coral. (Solvin Zankl Geomar)

The massive project might be done for now, but it continues to serve as a model for other marine scientists.

Researchers in South America are already preparing to undertake a similar project in the southern Atlantic ocean, which is far less explored, and exploration is set to finish in 2023.

Who knows what treasures of the deep we'll find this time.