POSTER SESSION 4
10:30–12:30, Thursday, September 17
Poster Session | 1 | 2 | 3 | 4 | Schedule at a Glance
ABSTRACT 1315 | POSTER 136
IDENTIFYING POTENTIAL OPTICAL INDICATORS OF HAB EVENTS USING SENTINEL-2/3 SATELLITES
Harmful algal blooms (HABs) have severe implications for aquatic ecosystems and coastal economies, but remain difficult to monitor due to their diversity and complex environmental forcing. Satellite remote sensing has advanced HAB detection, as specific algal taxa exhibit unique spectral signatures. However, most studies have relied on low-resolution imagery and focused on few bloom events. This study aims to detect and discriminate blooms of key toxic phytoplankton taxa (Pseudo-nitzschia spp., Dinophysis spp., Gymnodinium catenatum, and Alexandrium spp.) across different coastal domains, using Sentinel-2 (10 m) and Sentinel-3 (300 m). Satellite images were retrieved from the Copernicus Open Access Hub during selected HAB events reported in the Harmful Algae Event Database and scientific literature, and processed into surface reflectance using ACOLITE. Multiple radiometric indicators were applied to optimize bloom patch detection. K-means clustering was used to characterize and discriminate reflectance spectra of the four groups. Reflectance spectra displayed peaks at 560 and/or 704 nm, with variable peak patterns among taxa. The normalized difference chlorophyll index identified Pseudo-nitzschia spp., Dinophysis spp. and G. catenatum blooms, whereas the normalized difference Noctiluca index better identified Alexandrium spp. blooms. The best differentiation was obtained by combining standardized remote-sensing reflectance with normalized indexes for both satellite missions. Sentinel-3 differentiated blooms of Pseudo-nitzschia spp. and Dinophysis spp. Yet, due to the lower spectral resolution, Sentinel-2 did not discriminate any specific group. This study improved our understanding of HAB optical diversity and can support the use of satellite-derived optical properties as predictors in future HAB modelling approaches.
Maria Lima*, University of Algarve, [email protected], https://orcid.org/0000-0001-9401-0661
Amália Maria Sacilotto Detoni, Institut des Substances et Organismes de la Mer, Nantes Université, [email protected]
Ana B. Barbosa, Centro de Investigação Marinha e Ambiental (CIMA), Universidade do Algarve, [email protected]
Isabel Caballero, Institute of Marine Sciences of Andalusia (ICMAN), Spanish National Research Council (CSIC), [email protected]
Poster Session | 1 | 2 | 3 | 4 | Schedule at a Glance
