An interplay between plasticity and parental phenotype determines impacts of ocean acidification on a reef fish

The impacts of ocean acidification will depend on the ability of marine organisms to tolerate, acclimate and eventually adapt to changes in ocean chemistry. Here, we use a unique transgenerational experiment to determine the molecular response of a coral reef fish to short-term, developmental and transgenerational exposure to elevated CO2, and to test how these responses are influenced by variations in tolerance to elevated CO2 exhibited by the parents. Within-generation responses in gene expression to end-of-century predicted CO2 levels indicate that a self-amplifying cycle in GABAergic neurotransmission is triggered, explaining previously reported neurological and behavioural impairments. Furthermore, epigenetic regulator genes exhibited a within-generation specific response, but with some divergence due to parental phenotype. Importantly, we find that altered gene expression for the majority of within-generation responses returns to baseline levels following parental exposure to elevated CO2 conditions. Our results show that both parental variation in tolerance and cross-generation exposure to elevated CO2 are crucial factors in determining the response of reef fish to changing ocean chemistry. ; This study was supported by the Office of Competitive Research Funds OSR-2015- CRG4-2541 from the King Abdullah University of Science and Technology (T.R., P.L.M., C.S. and J.L.R.), the Australian Research Council (ARC) and the ARC Centre of Excellence for Coral Reef Studies (P.L.M. and J.L.R.) and the University of Oslo (G.E.N.). We thank the Marine and Aquaculture Research Facilities Unit (JCU), Integrative Systems Biology Laboratory (KAUST) and Biosciences Core Laboratory (KAUST) for support and assistance. Figures 1 to 4 were produced by X. Pita, scientific illustrator at King Abdullah University of Science and Technology (KAUST).