Ocean acidification alters fish–jellyfish symbiosis

Symbiotic relationships are common in nature, and are important for individual fitness and sustaining species populations. Global change is rapidly altering environmental conditions, but, with the exception of coral–microalgae interactions, we know little of how this will affect symbiotic relationships. We here test how the effects of ocean acidification, from rising anthropogenic CO2 emissions, may alter symbiotic interactions between juvenile fish and their jellyfish hosts. Fishes treated with elevated seawater CO2 concentrations, as forecast for the end of the century on a business-as-usual greenhouse gas emission scenario, were negatively affected in their behaviour. The total time that fish (yellowtail scad) spent close to their jellyfish host in a choice arena where they could see and smell their host was approximately three times shorter under future compared with ambient CO2 conditions. Likewise, the mean number of attempts to associate with jellyfish was almost three times lowe...共生关系（symbiotic relationships）在自然界中极为常见，对个体适合度（individual fitness）与物种种群的维持均具有重要意义。全球变化（global change）正快速改变环境条件，但除珊瑚-微藻互作（coral–microalgae interactions）外，我们对全球变化将如何影响其他共生关系仍知之甚少。本研究旨在探究由人为CO₂排放（anthropogenic CO₂ emissions）增加引发的海洋酸化（ocean acidification），会如何改变幼鱼（juvenile fish）与其水母宿主（jellyfish hosts）之间的共生互作关系。按照“一切照旧”温室气体排放情景预测的本世纪末海水CO₂浓度升高条件下饲养的鱼类，其行为会受到负面影响。在可观测并感知宿主的选择竞技场（choice arena）中，与环境CO₂浓度条件下的幼鱼（黄尾鲹，yellowtail scad）相比，未来高CO₂浓度条件下的幼鱼贴近水母宿主的总时长仅约为前者的三分之一。同样，幼鱼尝试与水母建立关联的平均次数也几乎是对照组的三分之一……