A team of marine biologists has discovered what it believes to be several new species of underwater creatures, including never-before-seen sponges, corals and sea stars.

The researchers returned to Halifax Wednesday after three weeks in the Atlantic Ocean aboard the Hudson, a Canadian Coast Guard ship.

Their mission took them to an underwater canyon called the Gully, as well as areas of the North Atlantic known as the Flemish Cap and the Orphan Knoll.

Also on board the ship was ROPOS, a remotely operated vehicle fitted with a movable arm that made it possible for the researchers to reach depths never before explored.

Species found 3 km below surface

With the help of ROPOS, the 27 biologists from Nova Scotia, Newfoundland and Quebec collected video, images and biological samples three kilometres below the sea's surface.

"We went down 3,000 metres, which is as deep as we have ever gone in these waters here," said Ellen Kenchington of the Bedford Institute of Oceanography in Dartmouth, N.S.

"At those depths, we found new species that we think will be new to science as well as new species to Canada. They include sponges, corals and invertebrates like sea stars, and even small worm-like creatures."

In addition to the scientific knowledge gained from the mission, the samples and evidence collected will allow researchers to make recommendations related to fish stocks and areas in need of protection.

"The push has been to identify these — where are they, what are they — put the science into defining them and their role in relation to the fish communities," Kenchington said. "I think the driver behind this is that we're seeing fish stocks undergo changes, and we really don't know enough about the entire ecosystem that they are a part of."

Many of the species collected are so new to science that they have yet to be named.