CO2 Damages Fish Brains
London, Jan 22 (TruthDive): Rising levels of carbon dioxide emissions in the ocean may cause neural damage in fish, interfering with their ability to smell and making them more vulnerable to predators, a new study has suggested.
According to Professor Philip Munday of the ARC Centre of Excellence for Coral Reef Studies and James Cook University, carbon dioxide concentrations predicted to occur in the ocean by the end of this century will interfere with fishes’ ability to hear, smell, turn and evade predators.
High levels of human carbon dioxide emissions may be affecting the brains and central nervous system of sea fishes, thereby threatening their survival in the long run. Biologists were able to show that dissolved CO2 is directly damaging the fishes’ nervous systems.
“For several years our team have been testing the performance of baby coral fishes in sea water containing higher levels of dissolved CO2 – and it is now pretty clear that they sustain significant disruption to their central nervous system, which is likely to impair their chances of survival,” Prof. Munday said.
In their latest paper, Prof. Munday and colleagues reported world-first evidence that high CO2 levels in sea water disrupts a key brain receptor in fish, causing marked changes in their behaviour and sensory ability.
“Our early work showed that the sense of smell of baby fish was harmed by higher CO2 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.”
The team then examined whether fishes’ sense of hearing used to locate and home in on reefs at night and avoid them during the day – was affected.
“The answer is, yes it was. They were confused and no longer avoided reef sounds during the day. Being attracted to reefs during daylight would make them easy meat for predators.”
Other work showed the fish also tended to lose their natural instinct to turn left or right – an important factor in schooling behaviour which also makes them more vulnerable, as lone fish are easily eaten by predators.
The team’s latest research shows that high CO2 directly stimulates a receptor in the fish brain called GABA-A, leading to a reversal in its normal function and over-excitement of certain nerve signals.
Prof. Munday said that around 2.3 billion tonnes of human CO2 emissions dissolve into the world’s oceans every year, causing changes in the chemical environment of the water in which fish and other species live.
“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 CO2 itself is damaging the fishes’ nervous systems. This will create a direct and previously unknown threat to sea life,” Prof. Munday added.