Featured Research: Fish Behaving Badly in Acid Sea off PNG

(JCU MEDIA RELEASE) In a world-first study published on April 14, researchers have found that fish in the wild respond adversely to ocean acidification.

“Fish living at natural carbon dioxide seeps have abnormal behaviors similar to what we’ve observed in previous laboratory experiments,” says Professor Philip Munday, lead author of the study from the ARC Centre of Excellence for Coral Reef Studies (Coral CoE) at James Cook University. He adds that these carbon dioxide levels are similar to what is predicted for the oceans in the second half of this century.

“We see small fish being attracted to, instead of avoiding, the smell of their potential predators,” Professor Munday explains. “The fish also ignore the smell of their preferred habitats. They are more active and display riskier behaviors, venturing further away from shelter, which makes them even more vulnerable to predators.”

The collaboration involving the Coral CoE, Australian Institute of Marine Science, Georgia Institute of Technology, and the National Geographic Society is the first to move out of the laboratory and into the natural environment to study the effects of ocean acidification on fish.

The isolated “natural laboratory” where the study was conducted lies just off the coast of Papua New Guinea, where coral reef waters are naturally made acidic by carbon dioxide seeps.

Dr. Jodie Rummer, a co-author from the Coral CoE, notes that while higher carbon dioxide levels affect fish behavior, they do not appear to impact their athletic performance. “The metabolic rates of fish from the seep area were the same as fish from nearby healthy reefs,” Dr. Rummer explains. “So, it seems that future ocean acidification may affect reef fish behavior more than other aspects of their performance.”

Professor Munday highlights another important finding: fish behavior did not seem to improve, despite fish from the carbon dioxide seep residing in acidic waters throughout their lives. “This suggests that fish cannot adjust to rising carbon dioxide levels over a lifetime,” he says. “As a result, it is imperative that we study the ability of fish and other marine species to adapt to higher carbon dioxide levels. Adaptation can happen, but we don’t know if it will happen quickly enough to overcome these negative effects on behavior.”

The findings of this study are of particular concern to the millions of people in the tropics who depend on coral reefs for food security and livelihoods.

To view the source story and more details about the study, click here (external link).