Astonishing, Unfathomable, Irreplaceable – why we need to conserve our deep sea canyons

If you were to head out east across the Atlantic, eventually – over 100 km off the coast of Nova Scotia – you’d find yourself on the edge of the Scotian Shelf. Here the seafloor drops steeply to depths greater than that of the Grand Canyon, via channels cut into the seafloor that vary from narrow cuts to meandering valleys. Formed a long time ago by glaciers, these submarine canyons are home to a variety of benthic communities and create biological hotspots in the deep sea.

So, what lives in these canyons? Well, a keystone species in canyon ecosystems are cold-water corals, such as the bubblegum coral pictured below, that grow on hard surfaces at the bottom and on the walls of the canyons. They’re not plants, they’re animals too, but they spend their long adult lives attached to the sea floor providing important habitats for many other species. These canyons are also home to a host of other unique and astonishing creatures, such as sea pens, anemones, squid, octopus, and deep sea fish species. And this diversity isn’t only at the bottom – the surface currents attract all sizes of fish, as well as seabirds, and whales and dolphins. The endangered Northern bottlenose whale can be found year-round in these canyons, they travel from surface waters to the deepest parts of the canyon for food, spending up to an hour underwater and diving down to 1,500 metres.

There’s still a lot we don’t know about these submarine canyons – undiscovered species, unknown behaviours and occurrences, and many other mysteries of the deep – but what we do know is that these ecosystems are at risk from human threats. Climate change, harmful fishing practises, vessel collisions, entanglements, noise, and debris are just a few of the threats to canyon ecosystems, particularly given the slow growth and reproductive rates of many of these species.

Now is the time to act. We need more research to better understand the risks of human activities; reductions to ship speeds to avoid collisions; policies on pollution and dumping; prohibitions on offshore oil and gas activities; and stricter fisheries management measures. But perhaps one of the most effective tools for protecting biodiversity hotspots are marine protected areas (MPAs), clearly defined space dedicated and managed to achieve long-term nature conservation.

In 2004, the Gully became Canada’s first Oceans Act MPA to be designated in the Atlantic Ocean. At 40km in length and 15km in width, it’s the largest submarine canyon off eastern North America and is home to a resident population of endangered Northern bottlenose whales. As an MPA the Gully has a zone that is closed to all fishing activities to protect vulnerable ecosystems.

Earlier this year, the Eastern Canyons Conservation Area was established to protect additional canyon ecosystems from commercial bottom-contact fishing gear. The Gully MPA and Eastern Canyons Conservation Area are important sites for conservation, but they are not the only ones – there are other sites awaiting protection, and plenty of other canyons and sensitive offshore habitats all along the Scotian Shelf. By expanding our network of protected areas we can ensure long term biodiversity conservation of offshore ecosystems, but also support connectivity between populations and long term resiliency to climate change and human disturbance.

This year, CPAWS-NS and partners hosted canyon celebration events around Nova Scotia, to spread the word about these unique ecosystems and the need for conservation. The response from the event attendees was clear – Canadian’s care about deep sea canyons and want to see them protected.

Look out for more celebration events next summer!

Reanne