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

The effects of ocean acidification mediated by an increase in water pCO(2) 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 mu atm CO2) altered intermediary metabolism of gilthead seabream (Sparus aurata) compared to fish acclimated to current ocean values (440 mu atm 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.

Automated summary

Researchers found that exposure to high CO2 conditions for 5 weeks altered the intermediary metabolism of gilthead seabream, compromising the fish's physiological acid-base balance, while the liver and muscle countered these effects by increasing catabolic routes. These results demonstrate how relatively short-term water hypercapnia may disrupt the acid-base balance, osmoregulatory capacity, and intermediary metabolism in S. aurata.