Ocean acidification compromises energy management in Sparus aurata (Pisces: Teleostei)

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The effects of ocean acidification mediated by an increase in water pCO2 levels on marine organisms are currently under debate. Elevated CO2 concentrations in the seawater induce several physiological responses in teleost fish, including acid-base imbalances and osmoregulatory changes. However, the consequences of CO2 levels enhancement on energy metabolism are mostly unknown. Here we show that 5 weeks of exposure to hypercapnia (950 and 1800 μatm CO2) altered intermediary metabolism of gilthead seabream (Sparus aurata) compared to fish acclimated to current ocean values (440 μatm CO2). We found that seabream compromises its physiological acid-base balance with increasing water CO2 levels and the subsequent acidification. Intestinal regions (anterior, mid, and rectum) engaged in maintaining this balance are thus altered, as seen for Na+/K+-ATPase and the vacuolar-type H+-ATPase activities. Moreover, liver and muscle counteracted these effects by increasing catabolic routes e.g., glycogenolysis, glycolysis, amino acid turnover, and lipid catabolism, and plasma energy metabolites were altered. Our results demonstrate how a relatively short period of 5 weeks of water hypercapnia is likely to disrupt the acid-base balance, osmoregulatory capacity and intermediary metabolism in S. aurata. However, long-term studies are necessary to fully understand the consequences of ocean acidification on growth and other energy-demanding activities, such as reproduction.
En este trabajo, realizado en colaboración con el Dr. Juan Fuentes, del Centro de Ciências do Mar (Portugal), se han descrito una serie de alteraciones en la gestión de los recursos energéticos ante una acidificación del océano a medio plazo en un pez teleósteo. Con este estudio se pretende comprender un poco mejor el efecto del cambio climático sobre el metabolismo intermediario de una especie económicamente relevante en la acuicultura Europea y mediterránea. Se ha visto que, en tan sólo 5 semanas, estos animales movilizan sus reservas energéticas (lípidos, hidratos de carbono y amino ácidos) para hacer frente a la acidificación del agua. A largo plazo se prevé que el cambio climático afecte a los peces teleósteos de manera negativa, ralentizando su crecimiento corporal.