Impact of high CO2 concentrations on marine life: Molecular mechanisms and physiological adaptations of pH and ion regulation in marine fish

In this thesis, the impact of hypercapnia (elevated PCO2) on the mechanisms of ion regulation and on energy metabolism, as well as the patterns of genetic regulation in marine fish was studied. Hypercapnia had no impact on oxygen consumption of whole animals and isolated gills. However, the energy allocation in gills shifted significantly towards ion regulation, protein- and RNA-biosynthesis. From regulation patterns of branchial ion transporters a biphasic acclimation model was elaborated: Within the initial phase, pH recovery is supported by transient downregulation of Na /H -exchanger (NHE1), Na /HCO3--cotransporter (NBC1) and Cl-/HCO3--exchanger (AE1) and increase of Na /K -ATPase (NKA), while long-term elevated levels of NKA and NBC1 maintain the new ion equilibrium. Acute response of the total branchial transcriptome was studied by differentially regulated genes obtained from cDNA libraries. Further processes responsive to hypercapnia were identified, such as stress responses and shifts in metabolic fluxes. The key processes of hypercapnia acclimation identified in the present thesis may serve as sensitive biomarkers for future studies.