ClimateWire: Oxygen-deprived waters are spreading over the continental shelves off the Pacific Northwest, threatening the marine species that live there.
Since 2002, more hypoxic, or oxygen-short, waters from deep offshore areas are moving into shallower areas near the shore, but they are not close enough to get oxygen from waves. That’s a result of oxygen reduction in deep water, which some scientists say may be a worldwide problem due to climate change.
Oxygen levels in the Pacific Northwest have been falling dramatically, leaving the area’s plentiful fish, sea stars and marine worms without air. Monitoring during a hypoxic event revealed many dead marine animals that could not escape.
Researchers say that if the trend continues, large fish like marlin, tuna and sailfish will have to move to shallow waters, making them more susceptible to being caught by fishers. The biodiversity of sea life would also take a great hit.
A paper to be published in Deep-Sea Research describes hypoxic water as a global problem, since tropical low-oxygen zones have expanded around the world while subsurface oxygen decreases. A research team led by oceanographer Lothar Stramma found that hypoxic areas where large species cannot survive have grown to nearly 5.2 million square kilometers since the 1960s. However, the problem is more pronounced in the Pacific because the deep waters there have not reached the surface for a long time.
Among the species that could benefit from the oxygen drain is the Humboldt squid, which has seen its population increase. Jellyfish blooms could also see a rise. However, larval fish could die out, as could species that rely on such fish for food (Michael Tennesen, Scientific American, Feb. 23). – JP