Many cold-water corals act as bioengineers, forming complex, three-dimensional habitats that are beneficial for other species. Whether the cold-water coral biocenonsis in the Patagonian fjord region has a comparable ecological importance is yet not clear. Tethocyathus endesa (Cairns et al., 2005) is a recently discovered solitary scleractinian and besides Desmophyllum dianthus and Caryophyllia huinayensis one of the most frequent cold-water coral species thriving in the Chilean fjord region. In two Chilean fjords, year-round temperature measurements and a frame based census have been carried out to describe the temperature environment and to quantify abundance in relation to water depth and substrate inclination. T. endesa thrives in water temperatures between 9.61°C and 15.30°C and can reach maximum abundancies up to 1,161 individuals per m². It settles at substrates with an inclination between 71° and 145°. This study aims for a better understanding of the reaction of this cold-water coral in a changing ocean. Besides ocean warming, especially ongoing ocean acidification may have extensive impacts on all calcifying organisms. The fjord Comau exhibits horizontal and vertical pH-gradients, which resemble the values that are forecasted by the recent IPCC-report for the end of the next century. These conditions allow experiments along the natural horizontal pH-gradient that can provide estimations on the influence of changing water parameters on T. endesa. Two parameters, which can be used to predict the influence of these environmental changes, are growth and respiration rates. The long-term study (12 months) revealed an in situ-growth rate of 10.34 ± 4.34% yr-1 (0.03 ± 0.01% d-1), which is comparable to other cold-water coral species of this region. In the present in situ experiment, T. endesa specimens have been cross transplanted between a location with high pH of 7.87 ± 0.06 and a Total Alkalinity (TA) of 2.219 ± 0.020mmol/l and a location with a low pH of 7.66 ± 0.04 and a TA of 2.241 ± 0.031mmol/l, respectively. Corals moved to low pH-conditions showed mass increases of 10.51 ± 1.14% yr-1 (0.03 ± 0.00% d-1), which is comparable to the control group under high pH conditions with 9.82 ± 4.38% yr-1 (0.03 ± 0.01% d-1). This may indicate physiological adaptations of T. endesa, enabling this species to up-regulate internal pH in tissues where biologically induced calcification takes place. Specimens from the cross-transplantation experiment, which have been transplanted from high to low pH conditions showed no statistical difference in respiration rates (9.88 ± 4.52μmol O2 × cm2 × d-1) compared to their control group (8.05 ± 2.93μmol O2 × cm2 ×d-1). As shown by the present study, the scleractinian cold-water coral T. endesa has the ability to thrive in conditions with future acidified sea water. Although cold-water corals reveal the potential of calcification under decreased sea water pH, the underlying balancing mechanisms are suggested to be accompanied by energetic effort, leading to a reduction of energy for other physiological important processes.