An international team of scientists says rising carbon dioxide concentrations in sea water can cause significant damage to the brains of fish.
More than two billion tonnes of carbon dioxide emissions are dissolved into the world’s oceans each year causing changes in the chemical makeup of the water.
Professor Philip Munday told AM’s Bronwyn Herbert that they found marked changes in the behaviour and sensory ability of young coral fish.
PHILIP MUNDAY: Higher CO2 levels in the ocean, the sorts of levels that we might see by the end of this century if we continue on our current carbon dioxide emission trajectory. Those sort of CO2 levels they actually influence the behaviour of baby coral reef fish. We found that the things that can be altered are behaviours such as their ability to smell predators, to turn left or right, to hear the sounds of reefs. These things are altered.
We’ve known this for a little while but we haven’t really understood what the common mechanism is that has linked all these sorts of diverse changes in behaviour and sensory ability and in our new work what we’ve found is that it is interference with a certain neurotransmitter in the brain called the GABA(A) receptor that is actually responsible for all these sorts of diverse effects on behaviour.
BRONWYN HERBERT: How significant is that damaged caused?
PHILIP MUNDAY: Well, the sorts of changes that we see in the fish even though you might just look at them in an aquarium or something like that and they look okay, the sorts of changes in behaviour could actually be quite significant. For example we found that normally these little coral reef fish they avoid the smell of predators and that is obviously quite a good thing to do. You wouldn’t want to swim up next to your predator.
But if they experience a higher CO2 levels their responses change quite significantly and they can actually be attracted to the smell of predators and so obviously that could have some pretty serious consequences.
BRONWYN HERBERT: How is it that dissolved carbon dioxide in the water actually damages the nervous system of fish?
PHILIP MUNDAY: That is what we have been trying to find out is exactly how the higher carbon dioxide levels affect the nervous system of the fish or affect their behaviour and what happens is that when they are actually experience higher carbon dioxide levels, it causes acidosis or it causes a change in PH in their tissues much as just putting extra carbon dioxide into water changes the PH of water. So they get a change in the PH of their issues.
To compensate for that, to make their PH back to normal, they actually change the concentration of irons in their blood and we’ve known for a long time that fish were actually very, very good at this but what it turns out is that of course, there are no free lunches in this world and changing the iron concentration then has an effect on these neurotransmitters.
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