Adjustments of molecular key components of branchial ion and pH regulation in Atlantic cod (Gadus morhua) in response to ocean acidification and warming

• Published in: Comparative Biochemistry and Physiology Part B: Biochemistry and Molecular Biology
• Main Authors: Michael, Katharina, Kreiss, Cornelia M., Hu, Marian Yong-An, Koschnick, Nils, Bickmeyer, Ulf, Dupont, Sam, Pörtner, Hans-O., Lucassen, Magnus
• Format: Article in Journal/Newspaper
• Language: English
• Published: Elsevier 2016
• Subjects: atlantic cod; Gadus morhua; Ocean acidification
• Online Access: https://oceanrep.geomar.de/id/eprint/37094/; https://oceanrep.geomar.de/id/eprint/37094/1/1-s2.0-S1096495915002183-main.pdf; https://doi.org/10.1016/j.cbpb.2015.12.006

Marine teleost fish sustain compensation of extracellular pH after exposure to hypercapnia by means of efficient ion and acid-base regulation. Elevated rates of ion and acid-base regulation under hypercapnia may be stimulated further by elevated temperature. Here, we characterized the regulation of transepithelial ion transporters (NKCC1, NBC1, SLC26A6, NHE1 and 2) and ATPases (Na(+)/K(+) ATPase and V-type H(+) ATPase) in gills of Atlantic cod (Gadus morhua) after 4 weeks of exposure to ambient and future PCO2 levels (550 μatm, 1200 μatm, 2200 μatm) at optimum (10 °C) and summer maximum temperature (18 °C), respectively. Gene expression of most branchial ion transporters revealed temperature- and dose-dependent responses to elevated PCO2. Transcriptional regulation resulted in stable protein expression at 10 °C, whereas expression of most transport proteins increased at medium PCO2 and 18 °C. mRNA and protein expression of distinct ion transport proteins were closely co-regulated, substantiating cellular functional relationships. Na(+)/K(+) ATPase capacities were PCO2 independent, but increased with acclimation temperature, whereas H(+) ATPase capacities were thermally compensated but decreased at medium PCO2 and 10 °C. When functional capacities of branchial ATPases were compared with mitochondrial F1Fo ATP-synthase strong correlations of F1Fo ATP-synthase and ATPase capacities generally indicate close coordination of branchial aerobic ATP demand and supply. Our data indicate physiological plasticity in the gills of cod to adjust to a warming, acidifying ocean within limits. In light of the interacting and non-linear, dose-dependent effects of both climate factors the role of these mechanisms in shaping resilience under climate change remains to be explored.