Overview over the experiments performed on Carcinus maenas specimen of the Baltic Sea. A short-term incubation experiment was conducted in April 2009 and microarray analysis was performed on isolated RNA of gills of these animals exposed to control (nominal 39 Pa) and elevated (nominal 400 Pa) p CO2 for 3 and 7 days. The experiment was repeated in 2010 and this time, RNA was isolated for quantitiative real-time polymerase chain reaction (qRT-PCR) of gill 9 after 7 days. In parallel, a long-term experiment was performed on Baltic Sea C. maenas in 2009 by Appelhans et al. (under review), and RNA of gill 7 was isolated and analysed by qRT-PCR.