"Global environmental change and the rise of CO2 have been identified as a major threat to scleractinian corals and coral reefs. General predictions are that ocean acidification will be detrimental to reef growth and that 40 to > 80 % of present-day reefs will decline during the next 50 years. While the impact of global change on reef-building corals has been intensely studied, not much is known on the response of deep-sea, cold-water corals or azooxanthellate shallow water corals. Also, the role of coral-associated prokaryotes in coral calcification and the microbial response to variable pCO2 and temperature and its impact on host calcification needs to be addressed. To tackle these open questions experiments with Mediterranean deep and shallow water azooxanthellate corals under controlled lab conditions with varying pCO2 and temperature will be conducted. The choice to study corals from the Mediterranean has several reasons: 1) the Mediterranean is an enclosed system and can be regarded as a miniature ocean that is expected to react faster to global change than the open ocean; 2) in general all ""ecotypes"" of corals ranging from zooxanthellate, shallow water corals that are also known from tropical reefs to azooxanthellate deep, cold-water corals are actually present in the Mediterranean; 3) some tropical and cold water coral species in the Mediterranean are at their biogeographic distribution limits confined by temperature constraints, and as such the study of Mediterranean corals and their response to global change will likely result in the identification of ""tipping points"" in response to temperature and pH changes. A last point is that no model predictions exist on the carbonate chemistry of the Mediterranean, but data compilation is in progress (J. Orr, IAEA Monaco) and the study of Mediterranean corals can thus contribute to the modelling of Mediterranean response to anthropogenic CO2 and global warming."