Coral Reef Fish Can Adapt To Fluctuating Carbon Dioxide Levels: Study


A new research finds that fish living among the coral reefs are actually more resilient than initially thought. However, further testing showed that significantly high carbon dioxide levels still affect the behavior of coral reef fish.

Risky Behaviors On Coral Reef Fish

Previous studies have shown that ocean acidification, a result of increasing carbon dioxide levels, affects ocean inhabitants including coral reef fish. For instance, fish that were exposed to high levels of carbon dioxide exhibited lower response levels.

Further, coral reef fish have been seen to exhibit strange behavior in response to high carbon dioxide levels such as loss of learning capabilities, favoring one side when swimming, and exhibiting riskier behaviors.

Naturally, risky behaviors have significant impacts on certain fish populations as it makes them more susceptible to predators. However, researchers from James Cook University found that coral reef fish may be more resilient in response to high levels of carbon dioxide than previously thought.

Fluctuating Chemical Changes In Coral Reefs

In previous studies, researchers often used stable levels of carbon dioxide in their treatments, but researchers of the current study used a technique that they believe mimics the natural fluctuations of carbon levels in coral reefs more accurately.

In the natural setting, the levels of carbon dioxide in coral reefs are actually much lower during the day than during the night. Taking this fact into consideration, they reared clownfish and juvenile damselfish to test how these fluctuations may affect their behavior.

No More Risky Behavior

The researchers conducted two experiments. In the first experiment, they did similar experiments to previous studies, in which they exposed the fish to stable 750 μatm thereby prompting the expected erratic behavioral changes. In the second experiment, they also exposed the fish to 750 μatm but with fluctuations of 300 μatm.

What they found was that with the fluctuations, the clownfish and juvenile damselfish were actually more resilient to carbon dioxide's effect than previously observed. Interestingly, they did not exhibit the erratic behavior previously observed in other experiments.

The interesting results excite researchers as this shows reef fish's ability to adapt to ocean acidity, suggesting that perhaps the feared ecological implications of the unusual behavior are not as severe as previously thought.

Still Not Out Of The Woods

Despite the promising results, they also found that there is still a limit to the resilience and adaptability of reef fish when carbon dioxide levels reach 1,000 μatm. At those high levels, the fish still exhibited unusual behaviors even when treated with low-level fluctuations.

As such, despite showing signs of resilience, it's still important to reduce the levels of carbon dioxide that get absorbed into ocean water. What's more, the effects of climate change are not limited to ocean acidification as it also contributes to serious bleaching events in coral reefs worldwide.

The study was published in the journal Scientific Reports.

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