When Cherisse Du Preez smiles, I feel I’ve pressed a hidden button. A deep-sea spatial ecologist with Fisheries and Oceans Canada and adjunct assistant professor at the University of Victoria, Du Preez stands on the front lines of climate change’s most pervasive and pernicious effect: ocean warming. And yet, though she’s more informed than most on the state of the planet, a grin wasn’t on my bingo card for a discussion of the defining subject of our lives.
“You have to find where we’re at right now fascinating in some way,” she explains, “or all you’re left with is depression.”
She’s right to conjure the anthropological. When it comes to outcome and consequence, understanding human decision-making can be as important as the subjects it turns on. “I’ve seen the government put out what I thought was a real feel-good story and still get criticized,” she says of why administrators can shy away from publicizing wins for fear of losing the message in a storm of discord. “We’re not the best at boasting.”
We are not. Which is why most Canadians know little of a substantive national achievement: Marine Protected Areas, whose deep seafloor habitats are the focus of Du Preez’s research. By protecting marine ecosystems and biodiversity in discrete areas of the ocean, MPAs represent a powerful nature-based solution to mitigating impacts of both climate change and resource exploitation, contributing to both national and international protection goals while supporting cultures and economies in coastal communities.
Shrimp on a Farea sp. glass sponge. Photo by NEPDEP Expedition Partners, CSSF ROPOS.
A scale worm (a new species to science) on a bubblegum coral (Paragorgia arborea). The polyps on the coral are anemone-like individuals living in colonies that together make the coral. Photo by NEPDEP Expedition Partners, CSSF ROPOS.
Profound ideals. Deep, even. And Du Preez’s explanation of what’s being protected and why offers a fascinating look into the importance of the planet’s last frontier.
Designated in 2003, Canada’s Endeavour Hydrothermal Vents MPA was the first globally to focus on these idiosyncratic structures, placing the country at the forefront of deep-ocean protection. Discovered only in 1977 in the Galapagos, hydrothermal vents discharge magma-heated seawater that can be over 370 C from geologically active areas of the seafloor—typically where tectonic plates are spreading apart.
Given the depth of such environments and absence of sunlight for photosynthesis, scientists were stunned by the extraordinary biodiversity found there—organic industry soon identified as reliant on chemosynthesis, in which microorganisms create energy by reducing chemical compounds dissolved in the superheated waters. It was a revelation akin to discovering life on Mars, changing our fundamental understanding of both marine ecosystems and the evolution of life itself.
A squat lobster (Sternostylus iaspis) on a Pinulasma sponge, a new species of glass sponge. Photo by Photo by NEPDEP Expedition Partners, CSSF ROPOS.
Hydrothermal vents opened new chapters in marine biology, sparking a renaissance in seafloor exploration by both manned (remember Alvin?) and remote-operated vehicles (ROVs—think large underwater drones). If we were only just finding out about vents, what else was down there still to discover?
“Off the west coast, we have the world’s fastest-moving tectonic plates, as well as the smallest. And that makes it a very dynamic environment,” says Du Preez, who uses ROVs to map seafloor features at exceedingly fine scales. In addition to clocking her fair share of hydrothermal vents during eight-to-12-hour ROV dives piloted and monitored onscreen aboard ocean-going vessels, she’s discovered dozens of seamounts in Canadian waters: volcanic structures over 1,000 metres high that support their own biodiversity.
Hydrothermal vents proved to be not only variable in type but often chemically, thermally, and biologically unique, of importance to oceanic mineral cycling and carbon sequestration, and fragile and ephemeral in nature. In the enormity of the ocean universe, they are tiny, geo- and eco-diverse planets that exist for but moments in geological time. The need to protect as many as possible could not be clearer.
The first thing to understand about MPAs is that they aren’t the only tool we have for managing marine environments, Du Preez says, citing levers such as fishing closures in marine areas that can be species- or method-specific, permanent or short-lived. But MPAs feature unwavering federal protections: while some activities may be allowed within their bounds (for example, shipping, sportfishing, recreation), others are strictly prohibited—no bottom contact, no mining, no dumping, and no oil-and-gas exploration or extraction. Subsequent prohibitions may be added, subtracted, or modified to achieve specific conservation values (for example, limits on sound that may interfere with whales). “It’s an adaptive approach once it’s in place,” Du Preez says, “but the basic protections can’t be turned off.” And you can’t move the boundaries.
Born in South Africa and raised in Canada, Du Preez was a self-professed “sporty person” in love with the ocean, a competitive surfer and diver involved in filming whales and sharks, so her later vocation seemed natural—albeit hard won. Dyslexic, she wrangled a sports scholarship to attend university. “I flunked my first attempt but got into a reading and writing program that helped me pass my undergraduate degree,” she says. Followed by a doctorate and postdoctoral positions. And her choice to focus on the deep-ocean, the black void below 200 metres? “If you want your work to have the most impact, choose the biggest ecosystem on the planet—the one with the most animals,” she says, referencing Earth’s single largest continuous environment, the one most responsible for planetary equilibrium, covering some 65 per cent of its surface and representing 95 per cent of ocean volume and living space. “DFO offered me the opportunity to protect stuff that mattered not only to Canada but to the planet.”
That the deep ocean’s importance doesn’t immediately resonate with most isn’t entirely due to its numinosity, arcane nature, or gaps in education. Du Preez also blames scientists.
“The discovery of hydrothermal vents was going to reinvent how we viewed the way the planet functions, but we unconsciously othered the environment and biological communities found there by referring to them as ‘extraterrestrial’ and ‘alien,’” she muses, parsing a view that no longer serves, given current knowledge of the importance of chemosynthesis globally and that the ocean is Earth’s largest single generator of oxygen.
“Every second breath you take comes from the ocean,” she reminds me. “The deep sea has a real connection to your life. We are not the centre of the universe.”
Located some 250 kilometres off Vancouver Island and 2,500 metres below the surface, the whimsical names of Endeavour’s vent fields—including Sasquatch and Salty Dawg—belie its status as Canada’s first MPA and one of only four to have been designated off our Pacific coast. Eleven additional MPAs exist off our coasts, eight Atlantic and three Arctic, the latter hosting the largest, Tuvaijuittuq, at 319,411 square kilometres. Aimed at protecting, conserving, and understanding the High Arctic sea-ice ecosystem in an age of rapid ice loss (the name is Inuktut for “place where the ice never melts”), Tuvaijuittuq represents approximately 5.55 per cent of Canada’s marine protection target under a global “30×30” initiative enshrined in the 2022 United Nations Convention on Biological Diversity, which seeks to protect 30 per cent of Earth’s land and ocean areas by 2030.
Tuvaijuittuq also represents another element of modern MPAs: collaboration on long-term protection priorities between the Canadian government and Indigenous partners, including support for an Inuit-led protected and conserved area. Indeed, MPAs are now co-created with coastal Indigenous peoples. The process starts with a partner overview of what should be protected and why. Natural values of geodiversity and biodiversity are assessed along with the human dimension: what economic interests might be lost—or gained—by conserving these? After public comment, a final agreement is based on nation-to-nation cooperation.
Du Preez has likewise dedicated her work to knowledge co-creation and cooperative management and monitoring initiatives with Indigenous peoples. This was illustrated in the July 2024 co-designation by Canada and the Haida, Nuu-chah-nulth, Pacheedaht, and Quatsino Nations of Tang.ɢ̱wan – ḥačxʷiqak – Tsig̱is (a mashup of various nations’ references to the deep ocean: TḥT for short), a 133,019-square-kilometre MPA west of Vancouver Island brimming with seamounts and hydrothermal vents that benefited from Du Preez’s involvement start to finish.
Within TḥT, bottom-contact fishing was significantly harming seamounts, so an interim fisheries closure in 2017 that shut down pressure on the environment was maintained until the MPA could be thoroughly studied and officially established. Given the eight years between, a biological mind wonders whether this yielded measurable dividends. Du Preez’s answer says more about the fragility of the seafloor than any quantitative assessment could deliver.
“With the deep sea, the only metric for something being successful is stopping the destruction, because some things don’t come back fast enough for us to assess, ” she says. “For instance, corals and sponges destroyed by bottom trawling take centuries to recover, so the measure of success is basically that fishers stop catching coral.”
There is, however, now opportunity to examine “spillover effects,” a key objective of MPAs wherein some species reach capacity in protected ecosystems and individuals leave to populate adjacent unprotected areas—outflow from a healthy ecosystem to one under more pressure, as Du Preez puts it. “Fisheries all over the world are waking up to the fact that protecting critical places with MPAs can enhance activities outside of them.”
With a boundary 4.5 times the size of Vancouver Island, TḥT protects an even larger area comprising the three-dimensional space between seabed and surface, which, as Du Preez explains, swells with life. “More than 90 per cent of biomass in B.C. lives in the deep sea,” she says. “The majority of the province’s wildlife are tiny, gelatinous, bioluminescent animals that never see the light of day and speak to each other in flashes.”
Not only is it hard to wrap your head around the number of animals saved in protecting an area this large, she says, but also the deep-time biodiversity preserved. “We used to clock the oldest deep-sea corals at about 4,500 years old, but we’ve recently found some that are over 7,500 years old, so that makes preserving these species even more important.” Some of the rockfish in MPAs—things you can find in the supermarket—are as old as Canada.
Hydrothermal vent chimneys called “black smokers” for the minerals precipitating out of the superheated (up to 400 C) water as it comes into contact with the near-freezing ocean water. Photo by NEPDEP Expedition Partners, CSSF ROPOS.
A deep-sea octopus (Graneledone boreopacifica) in a field of carnivorous sponges (white sticks—only carnivorous to small plankton.) Photo by Photo by NEPDEP Expedition Partners, CSSF ROPOS.
But if physical threats to marine life are enough to raise eyebrows, they pale in comparison to the hammer of climate change. The ocean absorbs 90 per cent of Earth’s non-radiated heat but may be reaching its capacity for heat absorption—even the recent Los Angeles fires have been linked to record warm surface waters. “I just attended a climate meeting where someone observed the planet would already be cooked if it weren’t for the deep sea,” notes Du Preez, who, along with colleagues, suggested in a 2020 paper that the climate-driven ocean acidification and oxygen loss they measured could lead to a mass-mortality event within 100 years. It happened in five. In an area she calls “Spongetopia” near the Explorer Seamount, 90 per cent of sponges died of oxygen deprivation.
“For the deep sea, that’s unprecedented,” she says. “This isn’t just the fastest we thought a deep-sea animal could die off, but the first quantitative evidence that low oxygen is having these effects right now.”
All things considered, existing and pending MPAs represent something for the climate-anxious to celebrate and all of us to embrace. “All of the processes we’re engaged in to mitigate climate change are things that the deep ocean already does naturally,” Du Preez summarizes. “Earth without the deep seas is basically Mars—and that didn’t go so well for Matt Damon.”
Read more from our Spring 2025 issue.
