Seawater carbonate chemistry and activity levels of a coral reef fish@en

Levels of dissolved carbon dioxide (CO2) projected to occur in the world's oceans in the near future have been reported to increase swimming activity and impair predator recognition in coral reef fishes. These behavioral alterations would be expected to have dramatic effects on survival and community dynamics in marine ecosystems in the future. To investigate the universality and replicability of these observations, we used juvenile spiny chromis damselfish (Acanthochromis polyacanthus) to examine the effects of long-term CO2 exposure on routine activity and the behavioral response to the chemical cues of a predator (Cephalopholis urodeta). Commencing at ~3–20 days post-hatch, juvenile damselfish were exposed to present-day CO2 levels (~420 μatm) or to levels forecasted for the year 2100 (~1000 μatm) for 3 months of their development. Thereafter, we assessed routine activity before and after injections of seawater (sham injection, control) or seawater-containing predator chemical cues. There was no effect of CO2 treatment on routine activity levels before or after the injections. All fish decreased their swimming activity following the predator cue injection but not following the sham injection, regardless of CO2 treatment. Our results corroborate findings from a growing number of studies reporting limited or no behavioral responses of fishes to elevated CO2.据报道，未来全球海洋中预计将达到的溶解二氧化碳（CO₂）水平，会提升珊瑚礁鱼类的游泳活动，并削弱其对捕食者的识别能力。此类行为改变预计将对未来海洋生态系统的物种生存与群落动态产生显著影响。为探究上述观测结果的普适性与可重复性，本研究以幼年期棘光鳃鲷（Acanthochromis polyacanthus）为实验对象，考察长期CO₂暴露对其日常活动以及对捕食者（尾纹九棘鲈，Cephalopholis urodeta）化学信号的行为响应的影响。实验始于幼鱼孵化后3~20天，将受试幼鲷分别暴露于当前CO₂水平（约420 μatm）与2100年预测的CO₂水平（约1000 μatm），持续3个月的发育周期。随后，我们分别在注射海水（假注射，对照组）与注射含捕食者化学信号的海水前后，评估受试鱼的日常活动水平。CO₂处理对注射前后的日常活动水平均无显著影响。无论接受何种CO₂处理，所有受试鱼在注射捕食者化学信号后均会降低游泳活动，但在假注射对照组中无此行为变化。本研究结果与日益增多的相关研究结论一致，即鱼类对升高的CO₂水平仅存在有限的行为响应，或无响应。