Nova Scotia

Deep-sea biodiversity map finds surprising varieties of life

Brittle star samples from around globe show great diversity in deep, dark oceans

Deep Sea Diversity 20160511

A brittle star is shown in a handout photo.A humble, star-shaped creature that crawls across the floors of the seabed has helped a group of scientists that includes two Nova Scotian researchers come up with a map predicting surprising amounts of life in some of the world's deepest, darkest oceans. (HO-Nick Hobgood/The Canadian Press)

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A humble star-shaped creature that crawls across the floors of the seabed has helped a group of scientists that includes two Nova Scotian researchers come up with a map predicting surprising amounts of life in some of the world's deepest, darkest oceans.

The maps linking biodiversity to thousands of samples of the brittle star from around the globe came out on Wednesday in the journal Nature.

They suggest that deep waters such as those off Canada's continental shelves — once thought to be barren deeps — can have a greater density of some species than shallower and warmer waters.

Derek Tittensor, a biologist at Halifax's Dalhousie University, says the team collected 165,000 records from museums around the world over a 15-year period.

Big task

Giant file clam

A new species of giant file clam has been discovered in a deep underwater canyon called the Gully, about 220 kilometres off Nova Scotia. (Submitted by the Department of Fisheries and Oceans)

The findings were fed into a database that he and fellow Dalhousie biologist Boris Worm helped analyze, with the involvement of six other scientists including lead author Skipton Woolley, a doctoral candidate at the University of Melbourne.

"It was a huge effort compiling this information from sources dating back to a century or so and putting it together," said Tittensor in a telephone interview from his office at the United Nations Environment Programme World Conservation Monitoring Centre.

The database is a compilation of each variety of the brittle star, where it was found, the latitude and longitude and the depth where it was located.

Tittensor said co-author Tim O'Hara telephoned, emailed and visited museums where the samples were stored away after being scooped up off the ocean floor by methods such as trawls or deep-sea submersibles.

The team compiled the data to look for hot spots where there was a wide variety of brittle stars, as one indicator of biodiversity, said Tittensor.

"This is the only group at present for which we have enough information to put these distributions together," he said.

Brittle stars thrive in deep, frigid oceans

brittle star

A brittle star (top) and sand dollar captured at the bottom of Sable Gully, a 2.5-kilometre deep canyon located about 220 kilometres off the coast of Nova Scotia. (Department of Fisheries and Oceans )

The biologist explained that on land and in shallow oceans, biodiversity tends to peak in the tropics, but for the brittle stars, they found dense concentrations in areas such as the deep and frigid oceans off Canada's east coast.

"You tended to get the highest number of species at the mid latitudes," he explained. "Places like the central and North Atlantic or New Zealand, places quite far from the equator."

The density of the brittle stars thriving in the lightless waters of the deeps may be linked to areas where plankton production is raining chemical energy into the ecosystem, says the biologist.

"This is the first test as to how well those hypotheses explain biodiversity in the deep ocean," he said.

Marine 'snowfall' feeds deep sea creatures

benthic octopus

This benthic octopus is one of the creatures discovered in surveys of The Gully. (DFO)

The scientists say the seasonal cycles in the northern and southern hemispheres spark natural cycles that produce large-scale algal blooms in the spring and fall.

During the process, the plankton produced on the surface clump together and the energy-rich particles then cascade to the bottom of the oceans like marine snowfall, providing nutrients to the sea life that may be over two kilometres deep.

Tittensor says the science team is hoping that as more data from around the world is collected, global maps of sea floor diversity will continue to become more detailed and cover a wider range of marine life.

The data may also provide further support for protecting the ocean floors as governments plan to manage and conserve ocean areas, said the biologist.

"The implication ... in terms of planning to conserve an area is we'll need to take into account not just the shallow oceans but also the deep sea floors."

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