Oceanographic researchers have released a new paper showing worrying declines in oxygen levels in Queen Charlotte Sound, a large section of the British Columbia coast between Vancouver Island and Haida Gwaii. Its deep waters were once considered a refuge from low-oxygen conditions, but recent observations show seasonal and widespread occurrences of low oxygen—known as hypoxia—across large swaths of the continental shelf underlying Queen Charlotte Sound.
Researchers project that these harmful conditions will become more persistent in the coming decades—and that the deep waters in Queen Charlotte Sound will be largely hypoxic by 2050, with serious consequences for marine life and fisheries.
“Over the last few decades, we've seen a general decrease in oxygen in waters all over the globe, and the warning lights are flashing for the Central Coast of BC.” says Sam Stevens, an oceanographer and postdoctoral researcher at the Hakai Institute and lead author on the paper. “Now we're seeing a change in the ecosystem there. And if these trends continue, as we expect, hypoxia will continue to worsen in the coming decades.”
The study draws on nearly 20 years of data, along with intensive observations from 2022 and 2023, and was led by scientists from the Hakai Institute, the University of British Columbia (UBC), Fisheries and Oceans Canada, and the University of Victoria.
A large portion of the measurements from 2022 and 2023 were collected by the Canadian-Pacific Robotic Ocean Observing Facility (C-PROOF) using ocean gliders—autonomous underwater vehicles that traveled back and forth across Queen Charlotte Sound, diving from the surface to the seafloor to record oxygen levels, temperature, salinity, and other conditions in fine detail.
These declines in oxygen are largely caused by climate change, says Stevens, because as surface waters of the ocean get warmer it becomes harder for atmospheric oxygen to be mixed into the ocean via winds, storms, and tides. The team found a strong correlation between oxygen variability in Queen Charlotte Sound and conditions in subarctic waters off Japan and Russia, suggesting that changes in ocean conditions thousands of kilometers away are affecting oxygen supply to the Canadian shelf.
“The long-term changes that we're seeing now on the BC coastline actually seem to originate thousands of kilometers away across the Pacific,” says Stevens.
Warming causes seawater to hold less oxygen, but that explains only a small part of the loss. The bigger driver is that winters in the subarctic North Pacific are producing less cold, dense, oxygen-rich water, meaning less oxygen is delivered into the ocean’s interior—and eventually to BC’s coastal waters.
“These changes on the other side of the Pacific slowly make their way over to us here in BC, about eight to 10 years later,” says Stevens. “For most people, it would be quite surprising to learn that changes in the ocean near Japan are affecting the straits, inlets, and fjords of British Columbia.”
The authors estimate that by 2050, more than half of the Queen Charlotte Sound seafloor could be seasonally hypoxic. This shift has broad ecological implications.
"Over the last few decades, there have been mass die-offs of seafloor organisms in Oregon and Washington related to hypoxia, and it’s possible we’ll begin to see similar events occurring here in BC," Stevens says.
Hypoxia on the continental shelf has been linked to stress, displacement, and mortality in marine species such as crabs and rockfish, and could affect deep inlets and fjords that rely on Queen Charlotte Sound for oxygen-rich water—including Bute Inlet, Knight Inlet, and Rivers Inlet.
With the region entering this new regime, the researchers call for enhanced monitoring and modeling efforts to better anticipate and manage future changes.
“Queen Charlotte Sound supports valuable fisheries, biodiversity hotspots, and protected areas,” says Stevens, noting that the paper’s findings underscore the urgency of tracking both long-term oxygen trends and short-term variations, as well as the regional and global forces that drive them.
This would entail continued ocean glider monitoring, as well as developing “detailed physical and biogeochemical models and careful ecosystem monitoring for fish and seafloor invertebrates,” says Stevens. “The warning signs are there, and we need to keep a close eye on these troubling developments using all the tools at our disposal.”
Contact
Samuel Stevens
T: 672-200-2726
E: sam.stevens@hakai.org
Media Kit
A kit containing this press release PDF and images can be found at this link.
About the Study
This study was conducted by members of the Canadian-Pacific Robotic Ocean Observing Facility (C-PROOF), a partnership involving the University of Victoria, the University of British Columbia, Fisheries and Oceans Canada, and the Hakai Institute. This partnership focuses on using autonomous platforms—such as ocean gliders, moorings, and floats—to collect important oceanographic and ecological data in remote regions of the Canadian Pacific.
Title: Dissolved Oxygen Variability on the Canadian Pacific Shelf: Trends, Drivers, and Projections in the Context of Emerging Hypoxia in Queen Charlotte Sound
Journal: Global Biogeochemical Cycles
DOI: https://doi.org/10.1029/2025GB008608
