Surfclam fisheries rely upon wild-caught populations that currently are managed sustainably and responsibly. This species, however, may be sensitive to physicochemical changes, such as ocean acidification, in the habitat. As elevated carbon dioxide effects upon juvenile surfclam physiology have not been reported, a 3-month laboratory experiment was carried out to investigate this interaction. 1,200 surfclams, either fed or unfed, were exposed to three pCO2 levels (576, 1405, 2203 ppm). Every other week, growth, as well as physiological rates (feeding, respiration, ammonia excretion), were measured. Results revealed an appreciable decline in shell length and mass growth proportional to pCO2 concentration.This decline can be attributed to reduced feeding (clearance rate, assimilation efficiency) and/or increased in metabolic activity (respiration, ammonia excretion). Finally, experimental data have been used to calibrate a DynamicEnergy Budget (DEB) model describing energetic fluxes within an individual under simulated environmental conditions. The model was adapted to include pCO2 effects upon physiological rates to project the consequences of varied pCO2 upon whole-animal bioenergetics.