Description: Some studies have demonstrated that elevated CO2 concentrations in ocean waters negatively impact metabolism and development of marine fish. Particularly,early developmental stages are probably more susceptible to ocean acidification due to insufficient regulations of their acid-base balance. Transgenerational acclimation can be an important mechanism to mediate impacts of increased CO2 on marine species, yet very little is known about the potential of parental effects in teleosts. Therefore, transgenerational effects were investigated on life history in juvenile three-spined sticklebacks Gasterosteus aculeatus by acclimating parents (collected in April 2012, 55°03?N, 8°44?E) and offspring to ambient (~400 µatm) and elevated (~1,000 µatm) CO2 levels and measured parental fecundity as well as offspring survival, growth and otolith characteristics. Exposure to elevated CO2 concentrations led to an increase in clutch size in adults as well as increased juvenile survival and growth rates between 60 and 90 days post-hatch and enlarged otolith areas compared with fish from ambient CO2 concentrations. Moreover, transgenerational effects were observed in reduced survival and body size 30 days post-hatch as well as in enlarged otoliths at the end of the experiment, when fathers or both parents were acclimated to the high-CO2 environment. These results may suggest that elevated CO2 concentrations had rather positive effects on life-history traits of three-spined sticklebacks, but that parental acclimation can modify these effects without improving offspring fitness. Although the mechanistic basis of such transgenerational acclimation remains unclear, selective gradients within generations seem to determine the direction of transgenerational effects.

Description: Ocean acidification (OA), a direct consequence of increasing atmospheric CO2 concentration dissolving in ocean waters, is impacting many fish species. Little is known about the molecular mechanisms underlying the observed physiological impacts in fish. We used RNAseq to characterize the transcriptome of 3 different larval stages of Atlantic cod (Gadus morhua) exposed to simulated OA at levels (1179 µatm CO2) representing end-of-century predictions compared to controls (503 µatm CO2), which were shown to induce tissue damage and elevated mortality in G. morhua. Only few genes were differentially expressed in 6 and 13 days-post-hatching (dph) (3 and 16 genes, respectively), during a period when maximal mortality as a response to elevated pCO2 occurred. At 36 dph, 1413 genes were differentially expressed, most likely caused by developmental asynchrony between the treatment groups, with individuals under OA growing faster. A target gene analysis revealed only few genes of the universal and well-defined cellular stress response to be differentially expressed. We thus suggest that predicted ocean acidification levels constitute a “stealth stress” for early Atlantic cod larvae, with a rapid breakdown of cellular homeostasis leading to organismal death that was missed even with an 8-fold replication implemented in this study.