The influence of cross-generational warming on the juvenile development of a coral reef fish under ocean warming and acidification

Marine ecosystems are facing escalating chronic and acute environmental stressors, yet our understanding of how multiple stressors influence individuals is limited. Here, we investigated how projected ocean warming (+1.5 °C) during grandparental (F₁) and parental (F₂) generations of the spiny chromis damselfish (Acanthochromis polyacanthus), influences the sensitivity of F₃ juveniles to ocean warming (present-day vs +1.5 °C) and/or elevated CO₂ (490 μatm vs 825 μatm). After 16 weeks of exposure, aerobic physiology (resting oxygen consumption, maximum oxygen consumption, and absolute aerobic scope), behaviour (boldness and activity), and growth (length and physical condition) were measured in F₃ juveniles and the relationships between these performance traits was explored. We found that warming during F₃ development resulted in juveniles that were shorter, bolder, and in better physical condition, while elevated CO₂ resulted in shorter juveniles with a reduced resting oxygen consumption. However, across juvenile performance traits there was no interaction between ocean warming and acidification, demonstrating the additive nature of these two environmental stressors. Although we found limited signs of transgenerational plasticity, there was evidence of parental and grandparental carry-over effects which resulted in juveniles that were larger and/or in better condition when grandparents and parents experienced warming during their development regardless of the F₃ juvenile developmental treatment. These findings illustrate the significant role phenotypic plasticity has on juvenile performance under projected future climate change.