It really does seem that the Earth’s oceans are bearing the brunt of the effects of climate change thus far. Glacial melting has caused rising sea levels, warming sea temperatures have bleached coral reefs… and now ocean oxygen levels are dropping, which could put fish at risk.
A recent study by scientists at Germany’s Geomar Helmholtz Centre for Ocean Research found that ocean oxygen levels have fallen by 2% over the past 50 years. If climate change continues at its current pace, that level will reach as high as 7% by the year 2100.
This might not sound like a huge problem to us land-dwellers, but it spells bad news for marine life. Most marine organisms can’t adapt to low levels of oxygen, so as the ocean’s oxygen levels drop, so will the numbers of living creatures swimming around in those waters.
Callum Roberts, a marine conservation biologist at the University of York, explained the seriousness of the findings in an interview with The Guardian.
“What we’re seeing is fallout from global warming,” he said. “It’s straightforward physics and chemistry playing out in front of our eyes, entirely in keeping with what we’d expect and yet another nail in coffin of climate change denial.”
How does warmer weather equal oxygen-deprived ocean water? First, warmer water can’t hold as much oxygen as cold water. Next, even as the surface water manages to capture and hold onto a certain amount of oxygen, warmer water is less dense and doesn’t circulate, depriving the lower water levels the oxygen that marine creatures need to survive.
As areas of the ocean become deprived of oxygen, animals in those areas will be forced into increasingly smaller areas that still have enough oxygen for them to survive. This affects the overall ecosystem.
“Unless we address greenhouse gas emissions urgently we’ll see more and more of this,” Roberts said. “Life will become harder for creatures that live in the sea and for those that depend on them – i.e. us.”
By Dawn Henderson, Earth.com Staff Writer