New Australian study of the effects of rising CO₂ on the marine ecosystem

The Guardian reports, 14th April 2014 : “A study by the Australian Institute of Marine Science, James Cook University and the Georgia Institute of Technology found the behavior of fish would be “seriously affected” by greater exposure to CO₂.

Researchers studied the behavior of coral reef fish at naturally occurring CO₂ vents in Milne Bay, in eastern Papua New Guinea. They found that fish living near the vents, where bubbles of CO₂ seeped into the water, “were attracted to predator odour, did not distinguish between odours of different habitats, and exhibited bolder behaviour than fish from control reefs”.

The AIMS study found the diversity of fish at the CO₂ vents was not influenced by the extra carbon, but that fish’s nerve stimulation mechanisms were altered, meaning the smell of predators became alluring.

More than 90% of the excess CO₂ in the atmosphere is soaked up by the oceans. When CO₂ is dissolved in water, it causes ocean acidification, which slightly lowers the pH of the water and changes its chemistry. Crustaceans can find it hard to form shells in highly acidic water, while corals risk episodes of bleaching.

A report released last year, which had input from the University of Western Australia’s Oceans Institute, found global warming could cause oceans to become 170% more acidic by the end of the century, the fastest rate of acidification in the past 300 million years.

Hugh Sweatman, research scientist at AIMS, said: “The acidification of the ocean is much discussed because it’s potentially a gigantic thing. It’s the difference between normal water and soda water, if you like. Ocean acidification seems to reverse sensations in fish so that things that smell repulsive become attractive. The small change in pH has a big impact on the fish.

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