A Global Survey of Intense Surface Plankton Blooms and Floating Vegetation Using MERIS MCI

Abstract

The MERIS imager on the European Envisat satellite has spectral bands which give a new capability for detection of blooms and aquatic vegetation. We use MERIS data to compute MCI (Maximum Chlorophyll Index), which measures the radiance peak at 709 nm in water-leaving radiance, indicating the presence of a high surface concentration of chlorophyll a against a scattering background. The index is high in ``red tide'' conditions (intense, visible, surface, plankton blooms) and also when aquatic vegetation is present, leading to a ``red edge'' step increase in radiance. A bloom search based on MCI has resulted in detection of a variety of events in marine waters and lakes round the world, as well as detection of extensive areas of pelagic vegetation (Sargassum spp.) in the ocean, previously unreported in the scientific literature. Global MCI composite images are produced daily from all MERIS (daylight) passes of Reduced Resolution (RR) data, starting soon after MERIS launch, in June 2002. This paper describes the composites and gives examples of plankton bloom events that they have detected.