Life on mountains in the sea

Two marine biologists offer a glimpse of life at the bottom of the ocean during 2018, 2019 and 2020 seamount expeditions 
  • Aug 06, 2020
  • 1,251 words
  • 6 minutes
Expand Image

We lose sunlight quickly. Thirty meters down is already pitch black. The area illuminated by the beams of our lights seems modest for our mission. Imagine mapping the Rocky Mountains at night by flashlight. As marine bilogists studying seamounts, what we do is similar but, for the full effect, imagine an unexplored Banff is hidden below three kilometers of water. Our expeditions take place hundreds of kilometers offshore of British Columbia, in Pacific Canada’s other great alpine environment, the mountains in the sea. As we descend into the ocean, illuminated passersby become alien-like. The dark abyss is speckled with the bioluminescence of lantern fish, squids and gelatinous critters of all shapes and sizes. Passing below 1,000 meters depth, we enter the ocean’s midnight zone. While the base of the mountain can be another one to two thousand meters deeper, the water is already near freezing and the pressure a hundred times greater than that experienced at sea-level.

During a seamount expedition, we routinely start our dives on a gentle-sloping flank and “climb” to the steep summit using a submersible robot — picture a gondola ride up a mountain, but equipped with banks of lights, high-resolution video and still cameras, dexterous arms, manipulators, arrays of sensors, and instruments. This equipment allows us to document and study the extraordinary life found on and around seamounts.

When lava from a large deep-sea volcanic eruption forms a giant seamount, the abrupt edifice drastically change the local conditions, creating a hidden underwater island oasis of life in the otherwise open ocean. Rocky seamounts rise kilometers above the surrounding mud that covers the majority of the world’s ocean floor. The flanks act as a ramp, driving up cold, nutrient-rich water, which can cause a cyclonic flow to form around the summit. The mixing of upwelled water at the shallower sunlit depths is the perfect recipe for phytoplankton blooms (microscopic plant-like organisms), which fuel the marine food web. These conditions attract a diversity of life, from the cold-water corals and sponges that colonize the deep pillows of volcanic lava to transient whales, sharks and seabirds that feed on the high concentration of prey. The positive effects spill over, and crabs, sea stars, fish, octopuses and many other species abound. The abundance of animals, biological diversity, and structural complexity found on a seamount can rival that of tropical coral reefs.

And because seamounts are a hotspot of life, they can play an essential role in ocean health and sustainability. However, for the same reasons, seamounts worldwide are under increasing threat from overexploitation and climate change. In the Canadian Pacific, conservation concerns include bottom-contact fishing, shipping traffic, oxygen depletion and ocean acidification. In the High Seas, concerns also include the prospect of underwater mining. 

Expand Image
We explore life on mountains in the sea using deep-sea submersible robots. This is the first submersible dive ever to Explorer Seamount (2018), Canada’s largest underwater volcano. The illuminated glass bugle-like sponges are the biological structures that create Spongetopia and are a brand new species. (Photo: Ocean Exploration Trust, the Northeast Pacific Seamount Expedition partners)

To safeguard a complex of three incredible seamounts, the Council of the Haida Nation and the Government of Canada established the SGaan Kinghlas–Bowie Marine Protected Area in 2008. Located offshore of Haida Gwaii, the largest seamount stands over three-kilometers tall and rises within twenty meters of the water’s surface — nearly triple the height of Banff’s iconic Mount Rundle. Its summit is so shallow that it’s home to kelp forests and coastal animals, some of which are threatened, providing an offshore refuge for life to thrive in the absence of near-shore pressures. Traditional knowledge and scientific evidence tell us that this seamount was once a volcanic island that has since eroded back into the sea. The Haida have experienced an intimate interconnection with SGaan Kinghlas since time immemorial.

The near-shore tectonic activity found in the Canadian Pacific is a globally-rare phenomenon, and Canada is fortunate to have an abundance of seamounts and other associated deep-sea environments in its Pacific waters (and jurisdiction). In 2017, Fisheries and Oceans Canada proposed a new Pacific MPA to protect over 75 per cent of known Canadian seamounts, which includes all seamounts shallow enough to be directly impacted by human activities. The MPA will also protect all known Canadian hydrothermal vent fields, which are deep-sea hot springs created by the same tectonic activity as seamounts but that support endemic animals found nowhere else on Earth.

To better protect these deep-sea treasures, we need to understand them. Every summer for the past three years, DFO has led a team of researchers and communicators on an unprecedented seamount campaign. We have discovered and described over forty hidden seamounts. We collected species new to science and filmed never-before-seen animals, places, and behaviors. Surprisingly, we have encountered tropical animals around the seamounts — such as bottlenose dolphins — their shifting distributions attributed to climate change. On Canada’s largest seamount, Explorer, we discovered Spongtopia — a “Dr Suess” city of towering bugle-like glass sponges that are meters high. We have found and mapped many other forests made of fragile, long-lived habitat-creating corals and sponges. Like an old-growth forest, if damaged, it will take decades to centuries for these ecosystems to recover.

Expand Image
The hidden underwater topography of the Canadian offshore Pacific (coloured as if 3,000 m of water was removed), its mountain ranges including SGaan Kinghlas-Bowie (SK-B) and Explorer (E) seamounts, and the locations of the existing and proposed seamount Marine Protected Areas (in the north and south, respectively). (Photo: C. Du Preez, Fisheries and Oceans Canada)

While our expedition research aims to support science-based decision-making in the development of protection, our imagery — with its broad reach — plays an essential role, showcasing Canadian seamounts and the extraordinary and unique life they support. As Jacques Cousteau famously said, “People protect what they love.” Alpine environments have not been precluded from this truth despite their general remoteness and historical inaccessibility. Photographs and stories capturing the beauty and importance of mountains have often been enough to inspire awe and shape public opinion, moving people to act. We can only hope for similar success with seamounts as millions of viewers have watched our expedition livestream and highlight reels across Canada and around the world in over 130 countries. Canadians are incredibly fortunate that seamounts are our national heritage and in our power to understand and protect. Remove the water and these mountains are as much a part of Canada as the Rockies.

Cherisse Du Preez and Tammy Norgard are marine biologists based in B.C. at the Institute of Ocean Sciences (Sidney) and Pacific Biological Station (Nanaimo), research organizations within the Department of Fisheries and Oceans Canada (DFO). Cherisse specializes in studying deep-sea benthic ecology using remotely operated vehicles video surveys and ship-based mutlibeam sonar. Tammy is the Program Head of the Large Offshore Marine Protected Area.


Are you passionate about Canadian geography?

You can support Canadian Geographic in 3 ways:

Related Content

illegal wildlife trade, elephant foot, ivory, biodiversity


The illegal wildlife trade is a biodiversity apocalypse

An estimated annual $175-billion business, the illegal trade in wildlife is the world’s fourth-largest criminal enterprise. It stands to radically alter the animal kingdom.

  • 3405 words
  • 14 minutes
A mountain half covered in snow


Why mountains matter in Canada

They sustain us, enrich our lives and inspire us

  • 1287 words
  • 6 minutes


The otter, the urchin and the Haida

As the sea otter begins its long-overdue return to Haida Gwaii, careful plans are being laid to welcome them — and to preserve a prosperous shellfish harvest

  • 3015 words
  • 13 minutes
Climate strike Victoria BC


Why Canada should recognize its citizens’ environmental rights

David Boyd, a Canadian environmental lawyer and UN Special Rapporteur on Human Rights and the Environment, reveals how recognizing the human right to a healthy environment can spur positive action for the planet

  • 1444 words
  • 6 minutes