Seawater carbonate chemistry and behavioural and physiological performance of a juvenile reef fish

Many studies have examined the average effects of ocean acidification and warming on phenotypic traits of reef fishes, finding variable, but often negative effects on behavioural and physiological performance. Yet the presence and nature of a relationship between these traits is unknown. A negative relationship between phenotypic traits could limit individual performance and even the capacity of populations to adapt to climate change. Here, we examined the relationship between behavioural and physiological performance of a juvenile reef fish under elevated CO2 and temperature in a full factorial design. Behaviourally, the response to an alarm odour was negatively affected by elevated CO2, but not elevated temperature. Physiologically, aerobic scope was significantly diminished under elevated temperature, but not under elevated CO2. At the individual level, there was no relationship between behavioural and physiological traits in the control and single-stressor treatments. However, a statistically significant negative relationship was detected between the traits in the combined elevated CO2 and temperature treatment. Our results demonstrate that trade-offs in performance between behavioural and physiological traits may only be evident when multiple climate change stressors are considered, and suggest that this negative relationship could limit adaptive potential to climate change.

诸多研究已围绕海洋酸化（ocean acidification）与海洋变暖对礁鱼（reef fishes）表型性状（phenotypic traits）的平均效应展开探讨，结果显示其对行为表现与生理表现的影响存在变异，但通常呈负面效应。然而，这些性状之间是否存在关联、以及关联的本质为何，目前仍不明确。表型性状间的负相关关系可能会限制个体表现，甚至制约种群适应气候变化的能力。本研究采用全因子实验设计（full factorial design），探究了高CO₂与升温环境下幼龄礁鱼（juvenile reef fish）的行为表现与生理表现之间的关联。行为层面上，对警戒气味（alarm odour）的响应会因CO₂浓度升高而受到负面影响，但不受升温影响。生理层面上，有氧代谢范围（aerobic scope）在升温条件下会显著降低，但在CO₂浓度升高的环境中无此变化。在个体层面，对照组与单一胁迫因子处理组的行为性状与生理性状之间均未发现关联。但在CO₂浓度升高与升温共同作用的处理组中，二者间却存在显著的负相关关系。本研究结果表明，行为与生理表现间的性能权衡（trade-offs）仅在面临多重气候变化胁迫因子时才会显现，且该负相关关系可能会限制种群适应气候变化的适应潜能。