ABSTRACT
The world's oceans are acidifying and warming as a result of increasing atmospheric CO2 concentrations. The thermal tolerance of fish greatly depends on the cardiovascular ability to supply the tissues with oxygen. The highly oxygen-dependent heart mitochondria thus might play a key role in shaping an organism's tolerance to temperature. The present study aimed to investigate the effects of acute and chronic warming on the respiratory capacity of European sea bass (Dicentrarchus labrax L.) heart mitochondria. We hypothesized that acute warming would impair mitochondrial respiratory capacity, but be compensated for by life-time conditioning. Increasing PCO2 may additionally cause shifts in metabolic pathways by inhibiting several enzymes of the cellular energy metabolism. Among other shifts in metabolic pathways, acute warming of heart mitochondria of cold life-conditioned fish increased leak respiration rate, suggesting a lower aerobic capacity to synthesize ATP with acute warming. However, thermal conditioning increased mitochondrial functionality, e.g. higher respiratory control ratios in heart mitochondria of warm life-conditioned compared with cold life-conditioned fish. Exposure to high PCO2 synergistically amplified the effects of acute and long-term warming, but did not result in changes by itself. This high ability to maintain mitochondrial function under ocean acidification can be explained by the fact that seabass are generally able to acclimate to a variety of environmental conditions. Improved mitochondrial energy metabolism after warm conditioning could be due to the origin of this species in the warm waters of the Mediterranean. Our results also indicate that seabass are not yet fully adapted to the colder temperatures in their northern distribution range and might benefit from warmer temperatures in these latitudes.
FOOTNOTES
Competing interests
The authors declare no competing or financial interests.
Author contributions
Conceptualization: S.H., G.C., F.C.M.; Methodology: S.H., N.L., G.C., F.C.M.; Validation: S.H., F.C.M.; Formal analysis: S.H., G.C., F.C.M.; Investigation: S.H., L.C., N.L., G.C., F.C.M.; Resources: G.C., F.C.M.; Data curation: F.C.M.; Writing - original draft: S.H., F.C.M.; Writing - review & editing: S.H., L.C., G.C., F.C.M.; Visualization: S.H.; Supervision: G.C., F.C.M.; Project administration: F.C.M.; Funding acquisition: G.C., F.C.M.
Funding
This work was supported by the German Science Foundation (Deutsche Forschungsgemeinschaft, DFG) and part of the FITNESS project (DFG grants MA 4271/3-1 to F.C.M. and PE 1157/8-1 to M. Peck, University of Hamburg, Germany).
Data availability
Datasets of mitochondrial respiration and water conditions during rearing, as well as additional information on larval rearing are available online from PANGAEA (www.pangaea.de).
Supplementary information
Supplementary information available online at http://jeb.biologists.org/lookup/doi/10.1242/jeb.213017.supplemental
- Received August 23, 2019.
- Accepted October 1, 2019.
- © 2019. Published by The Company of Biologists Ltd
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