Will Increasingly Acidic Seawater Affect Fish Or Will They Adapt?

The world's oceans will be more acidic in the next 100 years. The change could cause certain types of fish to become more anxious and change their swimming patterns, the Los Angeles Times reported.

Researchers, however, were forced to rely on a lot of speculative data to complete their study. First, they had to estimate the ocean's acidity over the next 100 years. Second, they tested fish living in today's pH levels in waters meant to mimic the pH level in 100 years, meaning their study couldn't account for how fish may gradually adapt over the next century.

Still, the acidification of water, a consequence of global warming, could become a more pressing issue in the future; thus, the study could become a springboard into greater research.

Scientists chose the rockfish, found frequently along the California Coast, as its test species because of a previous study that found rockfish adjusted their blood in low-pH waters -- an adaptation that affects certain behaviors like anxiety, according to the LA Times.

One group of fish was placed in a tank of current seawater and another group swam in a tank filled with the future's more acidic water. After a week of acclimation, researchers placed them in another tank specially designed to test for anxiety. One side contained white panels and the other contained black panels. Anxiety-free fish, according to the tank's logic, would swim regardless of black or white panels, but anxious fish would swim only towards the black panels. The rockfish placed in low-pH water congregated only around the black panels, according to Martín Tresguerres, a marine biologist at the Scripps Institution of Oceanography who co-authored the study.

"They would go to the dark part of the tank and they wouldn't move," he said. "They just stayed there."

Anxiety could affect the rockfish's survival, which relies on navigating light sources in giant kelp forests to avoid predators and catch prey, the LA Times reported.

"It could mean these fish will move less and be hidden more in the kelp blades," Tresguerres said, "Or they could change their feeding and dispersal behavior."

It took 12 days for the fish to recover from their experience in the acidic waters. Given 100 years, Tresguerres said there is a chance that fish could adapt without consequence.