Assessment of Water Quality Parameters in the Hooghly Estuary, India, Using Sentinel-3 and Global Biogeochemical Analysis and Forecasts Products

The Hooghly Estuary plays a critical role in supporting both the livelihoods of a significant human population and maintaining marine biodiversity, thus necessitating regular and precise evaluations of its water quality. Analyzing various parameters like Chlorophyll-a, Total Suspended Matter (TSM), Kd490 (a proxy for turbidity), Adg443 for Coloured Detrital Organic Matter (CDOM) concentration, Sea Surface Temperature (SST), Nitrate, Phosphate, Silicate, pH, Dissolved Inorganic Carbon (DIC), and Molecular dissolved oxygen (DO) across seasons and years revealed distinct patterns. Leveraging datasets from OLCI, SLSTR, and the Copernicus Global biogeochemical analysis and forecast products, concentration maps and time series depicted significant fluctuations, notably during the monsoon and post-monsoon periods. During these seasons, elevated river discharges due to heavy rainfall led to increased sediment flow from adjacent land and tributaries, consequently raising nutrient levels. During the pre-monsoon and monsoon periods, higher values of SST and increased chlorophyll-a concentration were observed primarily attributed to intensified solar radiation. Notable effects from cyclonic storm in October 2022 were also observed. The analysis showcased strong correlations among different parameters. Nutrients (silicate, phosphate, nitrate) exhibited positive correlations with pH (ranging from 0.47 to 0.78) and negative correlations with DIC (ranging from - 0.25 to -0.83). Additionally, pH showed a positive correlation with DO (r = 0.67), while chlorophyll-a correlated notably with turbidity (r = 0.86) and TSM with CDOM (r = 0.59). These robust correlations substantiate the relevance of the datasets for understanding the dynamics of the Hooghly Estuary.