OXYGEN-starved waters have invaded the shallows off Oregon in the US, making a graveyard of a 70-kilometre stretch previously teeming with marine life.
Francis Chan of Oregon State University in Corvallis and his team sailed into the 鈥渄ead zone鈥� on 8 August to search for signs of life using a robotic submarine, but found little but corpses. This is the fifth year in a row that a dead zone has appeared in the region, but this year鈥檚 die-off has been the most severe, with dramatic drops in oxygen levels.
鈥淚n past years, we measured oxygen concentrations down to about 0.5 millilitres per litre of ocean water,鈥� says Chan. This year the levels have dropped to 0.1. Anything under 1.4 is considered hypoxic. Fish can sense the drop in oxygen and swim to safety, but most other life simply suffocates.
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Researchers think a recent shift in wind patterns is to blame. Northerly winds sweeping down the western seaboard cause an upwelling of water from the deep ocean, which is naturally rich in nutrients but low in oxygen. Though shifting winds indicate a regional change in climate, Chan is hesitant to blame the dead zone on global warming.
