Harmful algal blooms

Harmful algal bloom monitoring maps bloom extent, intensity proxies, trends, and alert context for lakes, reservoirs, estuaries, and coastal zones.^[1][2] Satellite ocean-colour and water-quality observations support bloom tracking through chlorophyll-a, cyanobacteria, and related water-colour indicators.^[1][3][2] Multimission Sentinel-2 and Sentinel-3 chlorophyll-a or phycocyanin products improve cyanoHAB monitoring across spatial and temporal scales.^[4] Remote sensing observes surface optical signals and does not by itself confirm toxin concentration or subsurface bloom absence.^[2] Surface-temperature retrievals provide bloom-favourable context, but temperature is not bloom detection.^[2]