Current status of seawater quality in Digha (India), northwestern coast of the Bay of Bengal

The present investigation was intended to assess the seawater quality of Digha (India) in the northwestern coast of the Bay of Bengal. Digha is a mesotidal coastal plain located between two major estuarine systems, i.e. Subarnarekha and Hooghly located respectively on the western and eastern sides of the West Bengal along the northeast coast of India. The sampling was made at nine stations at various distances. Significant seasonal variations in environmental parameters and nutrients were observed during the study period. Analyses of physicochemical characteristics of the study area indicated that the level of dissolved oxygen (DO), biological oxygen demand (BOD), total dissolved solid (TDS) and nutrients is within the permissible limit. The results clearly revealed that, though sewage discharge takes place in the coastal waters, the quality of the water was not affected. It may be due to the large quantity of estuarine water input from the Hooghly estuarine system that have enhanced dilution of discharged sewage in Digha coastal waters. Strong tidal activities, wave dynamics and coastal current further dilute the effluent water in the study area, resulting to the minimised sewage effect on coastal ecosystem. Further studies on the heavy metal concentration and benthic diversity can be assessed to understand the health of the ecosystem.