CO2-induced ocean acidification does not affect individual or group behaviour in a temperate damselfish

Open ocean surface CO2 levels are projected to reach approximately 800 µatm, and ocean pH to decrease by approximately 0.3 units by the year 2100 due to anthropogenic CO2 emissions and the subsequent process of ocean acidification (OA). When exposed to these CO2/pH values, several fish species display abnormal behaviour in laboratory tests, an effect proposed to be linked to altered neuronal GABAA­ receptor function. Juvenile blacksmith (Chromis punctipinnis) are social fish that regularly experience CO2/pH fluctuations through kelp forest diurnal primary production and upwelling events, so we hypothesized that they might be resilient to OA. Blacksmiths were exposed to control conditions (pH ∼ 7.92; pCO2 ∼ 540 µatm), constant acidification (pH ∼ 7.71; pCO2 ∼ 921 µatm) and oscillating acidification (pH ∼ 7.91, pCO2 ∼ 560 µatm (day), pH ∼ 7.70, pCO2 ∼ 955 µatm (night)), and caught and tested in two seasons of the year when the ocean temperature was different: winter (16.5 ± 0.1°C) and sum...