Data on environmental oxygen levels among anemone tentacles from Anemone bleaching increases the metabolic demands of symbiont anemonefish

Increased ocean temperatures are causing mass bleaching of anemones and corals in the tropics worldwide. While such heat-induced loss of algal symbionts (zooxanthellae) directly affects anemones and corals physiologically, this damage may also cascade on to other animal symbionts. Metabolic rate is an integrative physiological trait shown to relate to various aspects of organismal performance, behaviour and locomotor capacity, and also shows plasticity during exposure to acute and chronic stressors. As climate warming is expected to affect the physiology, behaviour and life-history of animals, including ectotherms such as fish, we measured if residing in bleached versus unbleached sea anemones (Heteractis magnifica) affected the standard (i.e. baseline) metabolic rate and behaviour (activity) of juvenile orange-fin anemonefish (Amphiprion chrysopterus). Metabolic rate was estimated from rates of oxygen uptake (ṀO2) and the standard metabolic rate (ṀO2.min) of anemonefish from bleached anemones was significantly higher by 8.2% compared with that of fish residing in unbleached anemones, possibly due to increased stress levels. Activity levels did not differ between fish from bleached and unbleached anemones. As ṀO2.min reflects the minimum cost of living, the increased metabolic demands provide a likely explanation for the negative impacts of bleaching on important anemonefish life-history and fitness traits observed previously (e.g. reduced spawning frequency and lower fecundity).

全球热带海域的海水温度升高正导致海葵与珊瑚发生大规模白化现象。这种由高温引发的藻类共生体（zooxanthellae，虫黄藻）流失，不仅会直接从生理层面影响海葵与珊瑚，其损害还可能级联波及其他动物共生体。代谢速率是一项整合性的生理特征，已被证实与生物体的运动表现、行为模式及运动能力等多个维度相关，同时在暴露于急性与慢性胁迫时会表现出可塑性。鉴于气候变暖预计会对包括鱼类在内的外温动物的生理状态、行为模式与生活史特征产生影响，本研究检测了栖息于白化海葵（Heteractis magnifica，巨型海葵）与未白化海葵中的幼年橙鳍海葵双锯鱼（Amphiprion chrysopterus）的标准（即基础）代谢速率与行为（活动水平）是否存在差异。代谢速率通过耗氧率（ṀO2）进行估算，结果显示，栖息于白化海葵中的小丑鱼其标准代谢率（ṀO2.min）较栖息于未白化海葵的个体显著升高8.2%，这可能与胁迫水平上升有关。两类海葵中小丑鱼的活动水平并无显著差异。由于ṀO2.min代表了最低生存能耗，升高的代谢需求可合理解释此前观测到的海葵白化对小丑鱼关键生活史与适合度性状的负面影响（如产卵频率降低、繁殖力下降）。