Study: Carbon Dioxide Is “Driving Fish Crazy”

Rising human carbon dioxide emissions may be affecting the brains and central nervous system of sea fishes with serious consequences for their survival, an international scientific team has found.

AsianScientist (Jan. 3, 2012) – Rising human carbon dioxide emissions may be affecting the brains and central nervous system of sea fishes with serious consequences for their survival, an international scientific team has found.

In a paper published in the latest issue of the journal Nature Climate Change, Professor Phillip Munday and colleagues from the ARC Center of Excellence for Coral Reef Studies and James Cook University showed that high carbon dioxide concentrations in seawater disrupt a key brain receptor in the fish, impairing their ability to hear, smell, turn, and evade predators.

“We’ve found that elevated carbon dioxide in the oceans can directly interfere with fish neurotransmitter functions, which poses a direct and previously unknown threat to sea life,” said Prof. Munday.

Prof. Munday and his colleagues began by studying how baby clown and damsel fishes performed alongside their predators in carbon dioxide-enriched water. They found that, while the predators were somewhat affected, the baby fish suffered much higher rates of attrition.

“Our early work showed that the sense of smell of baby fish was harmed by higher carbon dioxide in the water – meaning they found it harder to locate a reef to settle on or detect the warning smell of a predator fish. But we suspected there was much more to it than the loss of ability to smell,” he said.

Other work showed the fish also tended to lose their natural instinct to turn left or right – an important factor in schooling behavior which also makes them more vulnerable, as lone fish are easily eaten by predators.

“All this led us to suspect it wasn’t simply damage to their individual senses that was going on – but rather, that higher levels of carbon dioxide were affecting their whole central nervous system,” he said.

The report states that high carbon dioxide levels lead to an overstimulation of a receptor in the fish brain called GABA-A, leading to a reversal in its normal function and over-excitement of certain nerve signals.

While most animals with brains have GABA-A receptors, the team considers the effects of elevated carbon dioxide are likely to be most felt by fish and crustaceans, as they have lower blood carbon dioxide levels normally.

2.3 billion tons of human carbon dioxide emissions dissolve into the world’s oceans every year, said Prof. Munday. This extensive amount of carbon dioxide comes from the burning of fossil fuels, changes in land-use, and primarily from deforestation.

“We’ve now established it isn’t simply the acidification of the oceans that is causing disruption – as is the case with shellfish and plankton with chalky skeletons – but the actual dissolved carbon dioxide itself is damaging the fishes’ nervous systems,” he said.

The article can be found at: Nilsson GE et al. (2012) Near-future carbon dioxide levels alter fish behaviour by interfering with neurotransmitter function.

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Source: ARC Center of Excellence for Coral Reef Studies.
Disclaimer: This article does not necessarily reflect the views of AsianScientist or its staff.

Marla Lise has an honours degree in animal science and a masters degree in environmental science from the University of Western Australia.

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