A novel earth observation based ecological indicator for cyanobacterial blooms.

•A novel Cyanobacterial Bloom Indicator (CyaBI) targeted for the ecosystem assessment of eutrophication in marine areas is presented.•The indicator is presented applying seasonal algal bloom characteristics information derived from earth observation data.•The CyaBI was found to pass the three critical factors set for marine indicator development.•The Indicator measures the current status properly, the target setting is scientifically proven and it is connected to the ecosystem management.