Chlorophyll-a
D1. Physical and chemical oceanography and marine meteorologyDefinition
Pigment in phytoplankton commonly measured to estimate ocean primary productivity.
Chlorophyll-a is the primary photosynthetic pigment in phytoplankton and the standard proxy for phytoplankton biomass and ocean color. Satellite radiometers (SeaWiFS, MODIS, OLCI) retrieve surface concentration from the blue-to-green reflectance ratio, mapping bloom dynamics and global primary production. Concentrations span more than three orders of magnitude, from under 0.05 mg/m^3 in subtropical gyres to over 10 in coastal upwelling and bloom waters.