Climate change: Oceans running out of oxygen as temperatures rise
Climate change and nutrient pollution are driving the oxygen from our oceans, and threatening many species of fish.
That's the conclusion of the biggest study of its kind, undertaken by conservation group IUCN.
While nutrient run-off has been known for decades, researchers say that climate change is making the lack of oxygen worse.
Around 700 ocean sites are now suffering from low oxygen, compared with 45 in the 1960s.
Researchers say the depletion is threatening species including tuna, marlin and sharks.
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The threat to oceans from the nutrient run-off of chemicals such as nitrogen and phosphorus from farms and industry has long been known to impact the levels of oxygen in the sea waters and still remains the primary factor, especially closer to coasts.
However, in recent years the threat from climate change has increased.
As more carbon dioxide is released enhancing the greenhouse effect, much of the heat is absorbed by the oceans. In turn, this warmer water can hold less oxygen. The scientists estimate that between 1960 and 2010, the amount of the gas dissolved in the oceans declined by 2%.
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