Elevated CO2 and food ration affect growth but not the size-based hierarchy of a reef fish

Abstract [Related Publication]: Under projected levels of ocean acidification, shifts in energetic demands and food availability could interact to effect the growth and development of marine organisms. Changes to individual growth rates could then flow on to influence emergent properties of social groups, particularly in species that form size-based hierarchies. To test the potential interactive effects of (1) food availability, (2) elevated CO2 during juvenile development, and (3) parental experience of elevated CO2 on the growth, condition and size-based hierarchy of juvenile fish, we reared orange clownfish (Amphiprion percula) for 50 days post-hatching in a fully orthogonal design. Development in elevated CO2 reduced standard length and weight of juveniles, by 9% and 13% respectively, compared to ambient. While development under low food availability reduced length and weight of juveniles by 8% and 16% respectively, compared to high food. Parental exposure to elevated CO2 restored the length of juveniles to that of controls, but it did not restore weight, resulting in juveniles from elevated CO2 parents exhibiting 33% lower body condition when reared in elevated CO2. The body size ratios (relative size of a fish from the rank above) within juvenile groups were not affected by any treatment, suggesting relative robustness of group-level structure despite alterations in individual size and condition. This study demonstrates that both food availability and elevated CO2 can influence the physical attributes of juvenile reef fish, but these changes may not disrupt the emergent group structure of this social species, at least amongst juveniles.The full methodology is available in the Open Access publication from the Related Publications link below.

摘要 [相关出版物]：在预估的海洋酸化（ocean acidification）情景下，能量需求变化与食物可获得性改变可能通过交互作用，对海洋生物的生长发育产生影响。个体生长速率的变化继而可传递影响社会性群体的涌现特性（emergent properties），对于存在基于体型的等级制度（size-based hierarchies）的物种而言尤为显著。
为探究（1）食物可获得性、（2）幼体发育阶段高浓度二氧化碳（elevated CO₂）暴露、（3）亲本高浓度二氧化碳暴露这三个因素对幼鱼生长、体况与基于体型的等级制度的潜在交互影响，我们采用完全正交设计（fully orthogonal design），将公子小丑鱼（Amphiprion percula）在孵化后饲养50天。
与环境浓度二氧化碳组相比，高浓度二氧化碳环境下发育的幼体，其标准体长（standard length）与体重分别降低了9%与13%。而与高食物可获得性组相比，低食物可获得性环境下发育的幼体，其体长与体重分别降低了8%与16%。
亲本高浓度二氧化碳暴露可将幼鱼的体长恢复至对照组水平，但无法使其体重恢复至对照组状态；这导致在高浓度二氧化碳环境下饲养的、亲本曾暴露于高浓度二氧化碳的幼鱼，其体况较对照组低33%。
幼鱼群体内的体型比例（即某个体相较于其上级个体的相对体型）未受任何实验处理的影响，这表明尽管个体体型与体况发生了改变，但该社会性群体的群体级结构仍具有相对稳定性。
本研究表明，食物可获得性与高浓度二氧化碳暴露均可影响幼龄礁栖鱼类的身体属性，但这些变化并不会破坏该社会性物种的群体涌现结构，至少在幼体阶段是如此。
完整的实验方法可通过下方相关出版物链接获取，该出版物为开放获取文献。