The spectre\u00a0of\u00a0low-oxygen\u00a0\u201cdead\u00a0zones\u201d is\u00a0surfacing\u00a0along BC\u2019s\u00a0Central\u00a0Coast, threatening the region\u2019s rich marine ecosystems and fisheries.\u00a0<\/p>\n
Widespread hypoxia \u2014 when\u00a0oxygen\u00a0levels in the ocean fall below levels required by marine life \u2014 is being detected in the deep waters\u00a0of\u00a0Queen Charlotte Sound for the first time, said Sam Stevens, an oceanographer at the Hakai Institute and\u00a0lead author\u00a0of\u00a0a new study<\/a>.\u00a0<\/p>\n Aggravated worldwide by climate change<\/a>\u00a0since warmer oceans generally hold less\u00a0oxygen, marine hypoxia is now beginning to impact the sound, sandwiched between northern Vancouver Island and south\u00a0of\u00a0Haida Gwaii. Marine life, such as crabs, fish and a host\u00a0of\u00a0sea bed creatures like sea stars and anemones, begin to suffer from hypoxia when dissolved\u00a0oxygen\u00a0levels fall below two milligrams per litre, Stevens said.\u00a0<\/p>\n \u201cIn 2022 and 2023, we saw large areas below this threshold,\u201d he said, adding projections from the research data suggest marine\u00a0oxygen\u00a0levels will get significantly worse by mid-century. Preliminary data gathered during 2024 and to date in 2025 suggest that the region\u2019s deep waters continue to experience\u00a0oxygen\u00a0starvation.\u00a0<\/p>\n If that trajectory continues, by 2050, about half\u00a0of\u00a0the sea floor\u00a0of\u00a0the Queen Charlotte Sound could suffer hypoxia during summer, along with 40 per cent\u00a0of\u00a0the volume\u00a0of\u00a0deep water below 100 metres, he said.\u00a0<\/p>\n \u201cThat\u2019s a large fraction\u00a0of\u00a0the system,\u201d Stevens said. \u201cIt suggests big changes for ecosystems and the species that depend\u00a0on\u00a0them.\u201d<\/p>\n Marine die-offs and fisheries impacts<\/p>\n The research raises alarms about the future\u00a0of\u00a0some\u00a0of\u00a0Canada\u2019s most productive waters.<\/p>\n The deep waters\u00a0of\u00a0the sound shelter celebrated conservation areas, like ancient\u00a0glass sponge reefs<\/a>\u00a0and important commercial fisheries for groundfish like halibut, rock cod and hake. The region also falls within the\u00a0<\/a>Great Bear Sea<\/a>, or\u00a0BC\u00a0Northern Shelf bioregion, where a string\u00a0of\u00a0new marine conservation areas are being developed.\u00a0<\/p>\n The hypoxia levels\u00a0on\u00a0the\u00a0Central\u00a0Coast\u00a0raises the\u00a0threat\u00a0of\u00a0serious marine die-offs like those experienced in southern waters off the\u00a0coast\u00a0of\u00a0Washington and Oregon<\/a>, where in several instances in the past two decades, huge numbers\u00a0of\u00a0Dungeness crabs perished, said Stevens.\u00a0<\/p>\n Persistent low\u00a0oxygen\u00a0levels along the\u00a0Central\u00a0Coast\u00a0could also cause a shift in the distribution\u00a0of\u00a0fish, which unlike slower bottom dwelling creatures, will migrate away from hypoxic areas, he said.\u00a0<\/p>\n Data about changing\u00a0oxygen\u00a0levels can better help inform monitoring\u00a0of\u00a0fish stocks and conservation decisions, he noted.\u00a0<\/p>\n \u201cThat might look like managing the fisheries for certain species that might be more or less impacted by these conditions,\u201d Stevens said. Examining hypoxia data could help predict what areas in the region might be least affected \u2014 possibly acting as refuges for species needing protection. \u00a0<\/p>\n \u00a0Global drivers, local fallout<\/p>\n The new study also suggests that the local\u00a0oxygen\u00a0levels are being driven by global warming halfway across the globe in the subarctic waters near Japan and Russia, Stevens said.\u00a0<\/p>\n \u201cIt was particularly interesting to make the connection between the Queen Charlotte Sound and climate change processes happening thousands\u00a0of\u00a0kilometres away\u00a0on\u00a0the other side\u00a0of\u00a0the Pacific,\u201d he said.\u00a0<\/p>\n Oxygen\u00a0levels\u00a0of\u00a0deep waters arriving\u00a0on\u00a0the\u00a0coast\u00a0of\u00a0BC\u00a0appear to be affected by climate impacts\u00a0on\u00a0the massive ocean circulation system called the\u00a0North Pacific Gyre<\/a>\u00a0that rotates ocean water clockwise from North America west across the Pacific Ocean and back again.\u00a0<\/p>\n However, winters in the distant subarctic waters may be changing with global warming, lessening the mix\u00a0of\u00a0atmospheric\u00a0oxygen\u00a0into ocean waters as a result\u00a0of\u00a0storms and winds. Freshwater layers\u00a0on\u00a0the surface\u00a0of\u00a0the ocean, caused by melting ice, also act like a cap that makes it more difficult for\u00a0oxygen\u00a0to mix into deeper seawater for eventual transport back to North America.\u00a0<\/p>\n The combined effects mean there is less\u00a0oxygen\u00a0in deep ocean water when it returns to flow over the continental shelf along the\u00a0BC\u00a0coast\u00a0eight to 10 years later, he said.\u00a0<\/p>\n Additionally, the nutrient-rich but low-oxygen\u00a0water becomes even more hypoxic once it wells upward in coastal waters and triggers plankton growth. When organic matter and\u00a0dead\u00a0microscopic creatures from these plankton blooms sink as \u201cmarine snow\u201d into deeper water, bacteria breaking down the materials consume\u00a0oxygen, aggravating hypoxia, Stevens said.\u00a0<\/p>\n Ocean gliders an invaluable tool\u00a0<\/p>\n The research team drew\u00a0on\u00a0nearly 20 years\u00a0of\u00a0historical ocean data, much derived from shipboard studies. However, the new findings were discovered using robotic ocean gliders, Stevens said.\u00a0<\/p>\n