At least three-quarters of the world's ocean species remain unknown following a 10-year census of marine life, Canadian researchers say.

"We've estimated that for every species we know about, there's probably another three or four that we don't know, that have never been sampled by science," said Paul Snelgrove, a professor at the Memorial University of Newfoundland's Ocean Science Centre who led the group that compiled the results of the international Census of Marine Life.

Larger species tend to be better known, and when it comes to small invertebrates and microbes, "our level of knowledge is zero in many parts of the ocean," said Snelgrove Tuesday.

He was speaking during a break in a two-day meeting in Ottawa of Canadian marine biologists and representatives of ocean-focused federal agencies and departments such as Fisheries and Oceans.

Even in well-known areas of Canada's coast new species have been pulled up as recently as this past summer, including this possibly new species of sponge found near Nova Scotia in July. (Bedford Institute of Oceanography/Canadian Press)

The meeting is a Canadian follow-up to the census completed in 2010. Its goal is to figure out how to harness Canadian marine biodiversity expertise and apply it to make sustainable use of fish and other ocean resources.

Snelgrove said universities have a lot of the infrastructure and resources needed to keep tabs on the oceans and make informed decisions.

"So, partnerships between universities and federal agencies and between agencies, I think, are the only way that we can continue to do a better on job on sustainable oceans," Snelgrove said.

At the meeting, much of the focus was on how to decide the boundaries of protected marine areas.

"If we're going to give up those areas for activities like fishing … then we want to put them in areas where they're going to be most effective," Snelgrove said.

In the case of spawning cod, for example, the protected areas should be ones where the eggs and young are likely to survive, he said, and not places like the edge of a continental shelf where many eggs would get swept out to sea.

Meanwhile, there has been increasing recognition that even small, inedible species play an important role in the oceans by contributing to the balance of resources like nutrients, oxygen and a good base for the food chain, Snelgrove said.

"Species that we may not think are important to us, in fact, are because of other relationships to the environment … and also to the species that we do harvest," Snelgrove said. "If we're losing some of them, as we know we are, are we losing aspects of ocean health with them?"

Arctic, deep ocean largely unexplored

Knowledge about marine species in two areas of Canadian waters in particular is limited, Snelgrove said:

• The Arctic, because of the ice that covers much of it.
• The deeper areas of the ocean, because exploring them is expensive.

Even off Nova Scotia and Canada's Pacific coast, new species have been pulled up as recently as this past summer, said Verena Tunnicliffe, director of the VENUS, a group of underwater observatories near Vancouver and Victoria. She also holds a Canada Research Chair in deep oceans research at the University of Victoria.

Tunnicliffe addressed the conference Monday night with a talk called "Exploring the ocean frontiers — We have more to learn."

Even in locations where most species are known, a lot of research continues to slowly unravel how environmental factors interact with marine life. One example of this is the shipping lane of Vancouver harbour, where researchers are exploring how such factors as oxygen, temperature, carbon or even noise affect plankton blooms and zooplankton.

"Theres's tonnes left to discover," she said. "This really is a major frontier."