Updated project metadata. Pacific oysters (Crassostrea gigas) were exposed to either 400 µatm (control) or 2800 µatm (ocean acidification) of pCO2 for 1 month. At the end of 1 month, half of the oysters from each pCO2 treatment were subjected to an additional mechanical stimulation. Gill (ctenidia) tissue was excised from 4 oysters from each of 4 treatments - 400 and 2800 µatm with and without mechanical stimulation. Tandem mass spectrometry was performed on all 16 samples on a LTQ Orbitrap XL with 3 technical replicates per biological sample.