Evaluation of water pollution in the estuary and adjacent coastal Bay of Bengal using water quality index and its implication to sustainable ecosystem management

Estuaries and coastal environment in the Bay of Bengal are affected by wide range of contaminants due to increased anthropogenic activity from a budding population in the coastal region. Sixteen physico-chemical and biological parameters were measured from 14 stations during four seasons like summer, monsoon, post-monsoon and winter along Mahanadi River, creek, estuarine and adjacent coastal ecosystem in 2011 and 2012. The results indicate that average lower value of pH (6.61 ± 0.68) was in winter, and dissolved oxygen (DO; 3.89 ± 2.01 mg L−1) was during monsoon in the ecosystem compared to the other season, whereas average higher concentration of Biochemical Oxygen Demand (BOD; 5.92 ± 2.62 mg L−1), nitrate (68.77 ± 30.35 µM), ammonium (43.50 ± 21.46 µM) and Phosphate (39.73 ± 10.63 µM) were found in the creek during post-monsoon. The ratio between nitrate and phosphate (N:P) declined in entire ecosystem of the study region indicated nutrient limiting due to the inorganic load into the system. The nutrients and phytoplankton biomass (Chlorophyll-a) show a strong positive correlation (r = 0.591) and negative correlation (r = −0.549) with BOD, respectively. Nutrients behaved non-conservatively and played a significant role in the depletion of DO. Factor analysis shows that loading activities of water quality parameters are mainly related to the major organic pollution, inorganic pollution and nutrients load into the ecosystem, whereas the cluster analysis and water quality index (WQI) resulted that the study region ecosystem has triggered alarm, due to various significant levels of contaminants. Hence, proper industrial management along with necessary measures is recommended for estuary and coastal environment ecosystem from socioeconomic disaster and sustainable ecosystem management.