Chlorophyll Bloom

A chlorophyll bloom is a phytoplankton bloom mapped through elevated chlorophyll-a, the photosynthetic pigment used as a proxy for algal biomass and primary production. Ocean-color satellites such as MODIS, VIIRS, and Sentinel-3 OLCI retrieve surface chlorophyll-a from water-leaving radiance, resolving bloom extent and timing across whole shelves and basins. Chlorophyll-a is the headline metric for trophic state and eutrophication assessment: the EU Water Framework Directive and OSPAR use chlorophyll-a percentiles to classify ecological status and nutrient enrichment. Concentrations span roughly 0.1 mg/m3 in oligotrophic open ocean to over 30 mg/m3 in eutrophic coastal blooms. Satellite series feed harmful-algal-bloom early warning.