Marine organisms must cope with environmental differences between the habitats they occupy through genetic, physiological and behavioral traits that allow them to adapt and survive across different spatial and temporal scales of climatic and oceanographic variation. Oxygen consumption of the bivalve mollusk Anadara tuberculosa was measured at two sites in the mangroves of Bahía de Chame (Pacific Panama), with contrasting pH and pCO2 levels. Oxygen consumption rates were recorded within the range of variability reported for other bivalve species (0.03 ± 0.02 mg/g/h). Small and random differences are reported between the marine-influenced site (0.02 - 0.04 mg/g/h) and the riverine-influenced site (0.01 - 0.06 mg/g/h). The observed variability appears to be a normal physiological response to the heterogeneous and highly variable environment of the estuaries and mangroves of Bahía de Chame.