Ocean acidification alters the way fish respond to predators

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Naturally occurring carbon dioxide seeps from seabed

Experiments conducted in Papau New Guinea reveal that fish exposed to higher concentrations of carbon dioxide were attracted to predator odor and had bolder behavior than fish from control reefs.  The study was located at an area with naturally-occurring carbon dioxide seeps.

The scientists found that the fish living on coral reefs with carbon dioxide seeping from the seabed had an impaired ability to smell and detect predators.  The conditions of the reefs that were under study had similar acidity that is expected to permeate oceans by 2100 if current levels of carbon dioxide emissions continue.

These findings verify experiments conducted in laboratories. There is little to no difference between the fish treated with carbon dioxide in the lab regarding tests on the fishes’ chemical senses versus fish living on the naturally occurring reef.  These fish are all able to smell but not distinguish between chemical cues.

This study, published in the journal Nature Climate Change, looked at fish from the “Bubble Reefs” at a natural carbon dioxide seep.  These seeps occur near volcanoes, which have acidity levels comparable to predicted levels of what the entire ocean could be at in the next 100 years.

Fish living under high carbon dioxide conditions were bolder than the control fish.  This means that they emerged more quickly from hiding places after a disturbance and ventured farther from this location. Control fish spent 80% of their time in hiding, while species at the acidified reef spent less than 23% of their time in shelter, preferring to swim in open water, making them more vulnerable.

These results were surprising because there has been a belief that fish could deal with ocean acidification due to their natural mechanism.  When fish are exposed to acidic conditions, the acid is absorbed into their bodies as they increase the amount of bicarbonate (a base) produced in their body.  Scientists found that when there is too much bicarbonate in the fish’s body, they have cognitive issues which the researchers observed.

 

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Journal Reference:

  1. Philip L. Munday, Alistair J. Cheal, Danielle L. Dixson, Jodie L. Rummer, Katharina E. Fabricius. Behavioural impairment in reef fishes caused by ocean acidification at CO2 seepsNature Climate Change, 2014; DOI:10.1038/NCLIMATE2195

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