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 mu atm, 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 GABA(A) 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 similar to 7.92; pCO(2) similar to 540 mu atm), constant acidification ( pH similar to 7.71; pCO(2) similar to 921 mu atm) and oscillating acidification ( pH similar to 7.91, pCO(2) similar to 560 mu atm ( day), pH similar to 7.70, pCO(2) similar to 955 mu atm ( night)), and caught and tested in two seasons of the year when the ocean temperature was different: winter ( 16.5 +/- 0.1 degrees C) and summer ( 23.1 +/- 0.1 degrees C). Neither constant nor oscillating CO2-induced acidification affected blacksmith individual light/dark preference, inter-individual distance in a shoal or the shoal's response to a novel object, suggesting that blacksmiths are tolerant to projected future OA conditions. However, blacksmiths tested during the winter demonstrated significantly higher dark preference in the individual light/dark preference test, thus confirming season and/or water temperature as relevant factors to consider in behavioural tests.