Paper Reviewed
Poulton, D.A., Porteus, C.S. and Simpson, S.D. 2017. Combined impacts of elevated CO2 and anthropogenic noise on European sea bass (Dicentrarchus labrax). ICES Journal of Marine Science 74: 1230-1236.

Writing as background for their work, Poulton et al. (2017) state that "ocean acidification is predicted to reduce the ocean's capacity to absorb low-frequency sounds produced from human activities." As a result, they hypothesize that "anthropogenic noise could propagate further under an increasingly acidic ocean" and alter certain behavioral and physiological traits of marine life. One important concern in this regard is that such noise will impair the startle response of fish to predatory strikes.

In a test of this hypothesis, Poulton et al. examined "the independent and combined impacts of elevated CO2 and [anthropogenic] noise on the behavior and physiology of the economically important European sea bass (Dicentrarchus labrax)." More specifically, they subjected juvenile European sea bass to a factorial experiment in which they crossed two CO2 levels (400 or 1000 ľatm) with two noise conditions (ambient and loud pile-driving) in a three-week-long analysis period. And what did their tests reveal?

In the words of the three United Kingdom researchers, "fish ventilation rate significantly increased during playback of pile-driving noise when compared with ventilation rate during ambient noise, supporting the hypothesis that pile-driving noise increases stress." However, they note that "the ventilation rate of fish exposed to elevated CO2 was not significantly different to that of control fish, indicating that elevated CO2 does not have an additional impact on the ventilator response of sea bass."

With respect to the significance of their findings, Poulton et al. say they show that "elevated CO2 has the potential to increase fish responsiveness to predators, potentially improving their chances of escape through reacting sooner to a threat stimulus," which suggests "that ocean acidification could have positive effects on the anti-predator behavior of D. labrax" (emphasis added).