Contrasting effects of ocean acidification on reproduction in reef fishes

Differences in the sensitivity of marine species to ocean acidification will influence the structure of marine communities in the future. Reproduction is critical for individual and population success, yet is energetically expensive and could be adversely affected by rising CO2 levels in the ocean. We investigated the effects of projected future CO2 levels on reproductive output of two species of coral reef damselfish, Amphiprion percula and Acanthochromis polyacanthus. Adult breeding pairs were maintained at current-day control (446 µatm), moderate (652 µatm) or high CO2 (912 µatm) for a 9-month period that included the summer breeding season. The elevated CO2 treatments were consistent with CO2 levels projected by 2100 under moderate (RCP6) and high (RCP8) emission scenarios. Reproductive output increased in A. percula, with 45-75 % more egg clutches produced and a 47-56 % increase in the number of eggs per clutch in the two elevated CO2 treatments. In contrast, reproductive output decreased at high CO2 in Ac. polyacanthus, with approximately one-third as many clutches produced compared with controls. Egg survival was not affected by CO2 for A. percula, but was greater in elevated CO2 for Ac. polyacanthus. Hatching success was also greater for Ac. polyacanthus at elevated CO2, but there was no effect of CO2 treatments on offspring size. Despite the variation in reproductive output, body condition of adults did not differ between control and CO2 treatments in either species. Our results demonstrate different effects of high CO2 on fish reproduction, even among species within the same family. A greater understanding of the variation in effects of ocean acidification on reproductive performance is required to predict the consequences for future populations of marine organisms.

海洋物种对海洋酸化的敏感性差异，将影响未来海洋群落的结构组成。繁殖对于个体存活与种群存续至关重要，但同时也需消耗大量能量，海洋中不断升高的二氧化碳浓度可能会对其产生不利影响。本研究针对两种珊瑚礁雀鲷的繁殖产出，探究了未来预估二氧化碳浓度水平的影响效应，受试物种分别为海葵双锯鱼（Amphiprion percula）与棘颊雀鲷（Acanthochromis polyacanthus）。实验将成年繁殖对置于当前环境对照浓度（446 微大气压）、中等浓度（652 微大气压）以及高浓度（912 微大气压）的水环境中饲养9个月，实验周期涵盖夏季繁殖季。上述二氧化碳浓度升高处理组，分别对应中等排放情景（Representative Concentration Pathways 6，简称RCP6）与高排放情景（Representative Concentration Pathways 8，简称RCP8）下2100年的预估二氧化碳浓度水平。在两种高二氧化碳浓度处理组中，海葵双锯鱼的繁殖产出均有所提升：产卵簇数量增加45%至75%，每簇卵的卵粒数量提升47%至56%。与之相反，棘颊雀鲷在高二氧化碳浓度环境下的繁殖产出出现下降，其产卵簇数量仅约为对照组的三分之一。二氧化碳浓度对海葵双锯鱼的卵存活率无显著影响，但棘颊雀鲷在高二氧化碳浓度环境下的卵存活率更高。高二氧化碳浓度环境下，棘颊雀鲷的孵化成功率同样更高，但二氧化碳浓度处理对幼体体型无显著影响。尽管两种鱼类的繁殖产出变化存在差异，但两个物种的成年个体体况在对照组与二氧化碳浓度处理组之间均无显著差异。本研究结果表明，即使是同科物种，高浓度二氧化碳对鱼类繁殖的影响效应也存在显著差异。未来需进一步明晰海洋酸化对繁殖性能的影响差异，方能精准预测其对海洋生物未来种群的影响后果。