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CO2 causes baby fish to get lost on their way home. Save Nemo, change a lightglobe!!

Just when you think headlines can’t be that stupid:

Baby fish may not find their way home as the level of CO2 in the ocean rises, study finds

— ABC  Isabel Dayman

Baby fish may lose their ability to find their way home in the future due to rising CO2 levels in the ocean, a marine ecology expert has found.

What the study found was that fish larvae were not paying attention to the right noises.

The researchers put the larvae in a tank and bubbled CO2 through it constantly. They appear to forget that CO2 changes naturally every night on reefs all over the world. Fish are not just used to having a daily shift, they prefer it. 

In shallow water, ocean acidification happens at 7pm daily, and after 400 million years, somehow, fish have adapted.

One previous study declared fish might become reckless in a high CO2 world, but later discovered that it was the laboratory setting that was the problem, not the CO2. When they added the daily pH swing back to their tanks, the fish behaved better and coped with the extra CO2. The real message is that laboratories are bad for fish.

As far as adapting to long term climate change, fish carry around hundreds of millions of years of assorted junk genes in the gene-pool, which help them cope when things change. (Remember the fish that adapted from salt-water to fresh-water in just fifty years?) Tools from past disasters may well linger on in a small proportion of the population. Natural selection can find that and amplify.

Barramundi have 32 million babies to lose at a time:

It’s gloom and doom on the ABC:

“When we raised these larvae under elevated CO2, we saw that those larvae were no longer attracted — and worse, they were deterred by — the natural sounds of their natural habitat,” he said.

And that will have devastating consequences because there will be no “recruitment”, or returning larvae, Professor Nagelkerken explained.

“The question is, what proportion of species will show this response — is it 10 of the fish species? Is it 50 per cent or 80 per cent?” he said.

Since one big Barramundi mother seriously does have 32 million eggs at a time, it might not be the end of the world if only 27% find their way home instead of 65%.

If it half the babies are wiped out, Barramundi numbers will drop temporarily — then five or six years later the new generation will be better adapted to higher CO2. One hundred years allows 20 generations of adaption. Like the  salt-water fish stuck in a fresh-water pool, natural selection is crushingly brutal but effective.  Spread over a century, fish will make it…

What’s next: CO2 causes bald kittens, and confused dogs?


Rossi et al, (2017)  On the wrong track: ocean acidification attracts larval fish to irrelevant environmental cues, Nature journal, Scientific Reports. You can read the whole paper. (Lucky you)

Previous studies:

Michael D. Jarrold, Craig Humphrey, Mark I. McCormick, Philip L. Munday. (2017) Diel CO2 cycles reduce severity of behavioural abnormalities in coral reef fish under ocean acidificationScientific Reports; 7 (1) DOI: 10.1038/s41598-017-10378-y (Freely available).

Kayanne et al (1995) Diurnal changes in the partial pressure of carbon dioxide in coral reef waterScience. 1995 Jul 14;269(5221):214-6. (Available at Researchgate.)

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