Ecological assessment of Hooghly River considering a few of the more perturbed sites based on some relevant physico-chemical and biological variables—A part of the AVIRIS-NG (NASA-ISRO) ground truth verification

Abstract A study was performed on a 32 Km stretch of the River Hooghly as part of a project under the Airborne Visible Infrared Imaging Spectrometer - Next Generation (AVIRIS-NG) scheme between Indian Space Research Organization (ISRO) and National Aeronautics and Space Administration (NASA). It was governed by 33 water quality variables comprising physical, chemical, biological and ecological ones. The selected stations were within the tidal realm of the estuary, constituting the lower-middle stretch of the river that was severely affected by anthropogenic perturbations. Chief biotic components studied were phytoplankton population density, primary and auxiliary phytopigments, and productivity in addition to chromophoric dissolved organic matter (CDOM). Majority of the study sites were observed with very low concentrations of dissolved oxygen along with significant shifts in primary production. Overall prevalence of Cyanophyceae and Bacillariophyceae was indicative of significant eutrophication. Reverse phase high performance liquid chromatography (HPLC) and radiometry revealed the presence of a large array of algal taxonomic groups through the detection of various primary and auxiliary phytopigments. The data and the study itself is of paramount importance being part of the ground truth verification initiative which will be used to render remote sensing techniques more precise in the future to better monitor the estuarine system.