Kwan et al.,Dryad_data_Final

Due to anthropogenic CO₂ emissions and the subsequent process of ocean acidification (OA), open ocean surface CO₂ levels are projected to more than double to ~1,000 μatm, and pH to decrease by ~0.3 units by the year 2100. 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 GABA_A receptor function. This study examined the effects of constant and oscillating OA-like conditions on individual and group behaviour of juvenile blacksmith (<i>Chromis punctipinnis</i>), a social fish that regularly experiences CO₂/pH fluctuations through kelp forest diurnal primary production and upwelling events. Blacksmiths were exposed to three treatments: control (pH ~7.92; pCO₂ ~540 μatm); constant acidification (pH ~7.72; pCO₂ ~920 μatm); and oscillating acidification (pH ~7.92, pCO₂ ~560 μatm (day), pH ~7.75, pCO₂ ~955 μatm (night)). After seven and eleven days, respectively, blacksmiths were administered individual light/dark preference and group shoaling tests, which are well-validated measures of anxiety-like behaviour and are modulated by GABA_A receptors. In addition, to investigate potential interactions between OA and season of the year, the effect of CO₂/pH on individual blacksmith behaviour was tested in January (16.50 ± 0.01^oC) and September (23.10 ± 0.01 ^oC). While season had a significant effect on light/dark preference, oscillating acidification did not affect any behavioural parameter, suggesting blacksmiths are tolerant to projected future OA conditions.