Acidification is one stressor expected to have wide spread impacts on the estuaries, which is keenly related to rapid industrialization, urbanization and change of land-use pattern. In addition to these man-made factors, there is growing evidence of tidal and gravitational currents that can deliver low pH and hypoxic marine waters into bays and estuaries. Input of low pH water from the open sea may be impounded by local eutrophication-triggered acidification and hypoxia in nutrient rich aquatic phase of the estuaries. These alterations have high probability to impact many species (preferably the biotic community with calcareous shell) important to functional ecology of the estuaries. Adverse impact on the survival, growth, recruitment of larval and juvenile shellfish is suspected to be amongst the earliest consequences of the phenomenon of estuarine acidification.