Ocean acidification (OA) is predicted to affect the physiology of some fishes. To date, most studies have investigated this issue using stable pCO₂ levels based on open ocean projections. Yet, most shallow, nearshore systems experience temporal and spatial pCO₂ fluctuations. For example, pCO₂ on coral reefs is highest at night and lowest during the day, but as OA progresses, both the average pCO₂ and magnitude of fluctuations are expected to increase. We exposed four coral reef fishes – Lutjanus fulviflamma, Caesio cuning, Abudefduf whitleyi, and Cheilodipterus quinquelineatus – to ambient, stable elevated, or fluctuating elevated pCO₂ conditions for 9-11 days. Then, we measured swimming performance, oxygen uptake rates, and haematological parameters during the day and at night. When compared to ambient pCO₂ conditions, L. fulviflamma, C. cuning, and A. whitleyi exposed to fluctuating elevated pCO₂ increased swimming performance, maximum oxygen uptake rates, and aerobic scope, regardless of time of day; whereas, the only nocturnal species studied, C. quinquelineatus, decreased maximum oxygen uptake rates and aerobic scope. Our findings suggest that exposure to fluctuating or stable elevated pCO₂ can physiologically benefit some coral reef fishes; however, other species, such as the cardinalfish examined here, may be more sensitive to future OA conditions.

预计海洋酸化（OA）将影响某些鱼类的生理。迄今为止，大多数研究都基于公开海域预测使用稳定的p CO ₂水平调查了这个问题。然而，大多数浅水近海系统都经历了时间和空间上的p CO ₂波动。例如，珊瑚礁上的p CO ₂在晚上最高，而白天则最低，但是随着OA的发展，预计平均p CO ₂和波动幅度都会增加。我们暴露了四种珊瑚礁鱼–褐鲷，Caesio cuning，Abudefduf whitleyi和Cheilodipterus quinquelineatus–在环境中，稳定的升高或波动的p CO ₂条件持续9到11天。然后，我们测量了白天和晚上的游泳表现，摄氧量和血液学参数。与周围的p CO ₂条件相比，暴露于变化的p CO _2的黄花苜蓿，C。cuning和A. whitleyi会增加游泳性能，最大摄氧率和有氧运动，而不论一天中的什么时间；而研究的唯一夜行物种，C。quinquelineatus，降低了最大摄氧率和有氧运动范围。我们的发现表明，暴露于波动的或稳定的升高的p CO ₂可以在生理上使某些珊瑚鱼受益。但是，其他物种，例如此处检查的红衣鱼，可能对未来的OA条件更加敏感。