Effects of ocean acidification on embryonic respiration and development of a temperate wrasse living along a natural CO(2) gradient

Volcanic CO(2) seeps provide opportunities to investigate the effects of ocean acidification on organisms in the wild. To understand the influence of increasing CO(2) concentrations on the metabolic rate (oxygen consumption) and the development of ocellated wrasse early life stages, we ran two field experiments, collecting embryos from nesting sites with different partial pressures of CO(2) [pCO(2); ambient (∼400 µatm) and high (800–1000 µatm)] and reciprocally transplanting embryos from ambient- to high-CO(2) sites for 30 h. Ocellated wrasse offspring brooded in different CO(2) conditions had similar responses, but after transplanting portions of nests to the high-CO(2) site, embryos from parents that spawned in ambient conditions had higher metabolic rates. Although metabolic phenotypic plasticity may show a positive response to high CO(2), it often comes at a cost, in this case as a smaller size at hatching. This can have adverse effects because smaller larvae often exhibit a lower survival in the wild. However, the adverse effects of increased CO(2) on metabolism and development did not occur when embryos from the high-CO(2) nesting site were exposed to ambient conditions, suggesting that offspring from the high-CO(2) nesting site could be resilient to a wider range of pCO(2) values than those belonging to the site with present-day pCO(2) levels. Our study identifies a crucial need to increase the number of studies dealing with these processes under global change trajectories and to expand these to naturally high-CO(2) environments, in order to assess further the adaptive plasticity mechanism that encompasses non-genetic inheritance (epigenetics) through parental exposure and other downstream consequences, such as survival of larvae.