Consequences of Climate Change: Carbon Dioxide, Fossil Fuels Force Fish to Switch to Permanent Night Mode

Global warming caused by human activity is not only affecting nature, but is also altering animal behavior.

Carbon dioxide from burning fossil fuels results to an acid harmful to marine life when released to oceans. This toxic substance forces fish to guard itself and adapt to a night defense mode even during the day.

According to the study published in the journal Nature, fish exposed to high levels of carbon dioxide are more vulnerable to predators as they respond slower to cues. This poses a threat to species and population survival, which forces the animals to adapt to their altered environments -- even if it involves flipping their body clocks.

The scientists came up with the above conclusion after observing adult and young damselfish living in Australia's Great Barrier Reef. The researchers studied two groups of parent damselfish: one sensitive to high carbon dioxide levels and one that's not.

The results showed that those who were naturally tolerant to high carbon dioxide concentration in water produced offspring that could tolerate ocean acidification, Phys.org reports.

"We developed a unique fish-rearing experiment that allowed us to measure the effects of ocean acidification across generations. By combining data from the genome with information about RNA and protein expression, we were able to uncover the transgenerational molecular responses of the fish's brains," said Timothy Ravasi, one of the study's authors.

Offspring of the tolerant damselfish also have altered circadian rhythm genes that enables them to adjust and adapt to their surroundings.

Normally, fish changes their bodies' defenses during the night as this is the time where carbon dioxide levels increase. However, for young fish with CO2-tolerant parents, permanently switching to a night body clock is more helpful in survival.

"Reef fish adjust their bodies to compensate for elevated night-time CO2, and of course, this is controlled by circadian rhythm," Ravasi said. "It seems the tolerant offspring may have adjusted their circadian clocks as if it was always night!"