Capability of space borne multispectral image for detecting discoloration in optically complex coastal waters

• Published in: Marine pollution bulletin Vol. 207; p. 116860
• Main Authors: Natarajan, Logesh, Vajravelu, Manigandan, Chandrasekaran, Muthukumar, Ramakrishnan, Sankar Ganesh, Kaviarasan, Thanamegam, Vipin Babu, P., Dash, Sisir Kumar, Ramu, Karri, Murthy, M.V. Ramana
• Format: Journal Article
• Language: English
• Published: England Elsevier Ltd 01.10.2024
• Subjects: Coastal pollution; Discoloration; NDCI; Puducherry; Remote Sensing Reflectance (Rrs); TSM; NDCI; Discoloration; Coastal pollution; Remote Sensing Reflectance (Rrs); Puducherry; TSM
• ISSN: 0025-326X; 1879-3363; 1879-3363
• DOI: 10.1016/j.marpolbul.2024.116860

Coastal pollutants, from harmful algal blooms, sewage and industrial discharges, pose severe risks to marine ecosystems and public health. Recently, Promenade Beach in Puducherry, Southeast-India, experienced reddish-brown water discoloration, suspected to result from either algal blooms or suspended matter. This study monitored the spatial extent and characteristics of the discoloration using Sentinel-2 satellite images from September to November 2023, with field observations and laboratory analyses. Analyses included measurements of chlorophyll-a (Chl-a), Total Suspended Matter (TSM), and the Normalized Difference Chlorophyll Index (NDCI) to differentiate between algal blooms and other pollutants. The satellite data indicated extents of discoloration, with high TSM concentrations (>45 g/m3) and negative NDCI values suggesting absence of algal blooms. No mortality of aquatic organisms was observed during this discoloration, indicating no deleterious impact on aquatic life. This approach highlights the importance of combining satellite technology with field data for effective coastal pollution monitoring, essential for protecting marine ecosystems. •Sentinel 2 data for monitoring water quality and coastal pollution•C2RCC Atmospheric correction was used to estimate Chl-a and TSM.•Discoloration due to suspended matter and not algal blooms