Ocean acidification is deadly threat to marine life, finds eight-year study

https://www.theguardian.com/environment/2017/oct/23/ocean-acidification-deadly-threat-to-marine-life-finds-eight-year-study

Fiona Harvey
Monday 23 October 2017

If the outlook for marine life was already looking bleak – torrents of plastic that can suffocate and starve fish, overfishing, diverse forms of human pollution that create dead zones, the effects of global warming which is bleaching coral reefs and threatening coldwater species – another threat is quietly adding to the toxic soup.

Ocean acidification is progressing rapidly around the world, new research has found, and its combination with the other threats to marine life is proving deadly. Many organisms that could withstand a certain amount of acidification are at risk of losing this adaptive ability owing to pollution from plastics, and the extra stress from global warming.

The conclusions come from an eight-year study into the effects of ocean acidification which found our increasingly acid seas – a byproduct of burning fossil fuels – are becoming more hostile to vital marine life.

“Since ocean acidification happens extremely fast compared to natural processes, only organisms with short generation times, such as micro-organisms, are able to keep up,” the authors of the study Exploring Ocean Change: Biological Impacts of Ocean Acidification found.

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Ocean acidification can reduce the survival prospects of some species early in their lives, with knock-on effects. For instance, the scientists found that by the end of the century, the size of Atlantic cod in the Baltic and Barents Sea might be reduced to only a quarter of the size they are today, because of acidification.

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Ocean acidification is another effect of pouring carbon dioxide into the atmosphere, as the gas dissolves in seawater to produce weak carbonic acid. Since the industrial revolution, the average pH of the ocean has been found to have fallen from 8.2 to 8.1, which may seem small but corresponds to an increase in acidity of about 26%.

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Worse still, the effects of acidification can intensify the effects of global warming, in a dangerous feedback loop. The researchers pointed to a form of planktonic alga known as Emiliania huxleyi, which in laboratory experiments was able to adapt to some extent to counter the negative effects acidification had upon it. But in a field experiment, the results were quite different as the extra stresses present at sea meant it was not able to form the extensive blooms it naturally develops. As these blooms help to transport carbon dioxide from the surface to the deep ocean, and produce the gas dimethyl sulfide that can help suppress global warming, a downturn in this species “will therefore severely feed back on the climate system”.