Average chlorophyll concentration in the surface ocean (from mi-September 1997 to August 2007) from the ocean color sensor SeaWiFS (NASA). Subtropical gyres, in the center of the oceanic basins, are characterized by very low concentrations of chlorophyll a (dark blue) - Source : NASA's Earth Observatory (http:/earthobservatory.nasa.gov)
Phytoplankton bloom observed in the Barents Sea (North of Norway) in August 2010 by the ocean color sensor MODIS onboard NASA satellite Aqua. Changes in ocean color result from modifications in the phytoplankton composition and concentration. The green colors are likely associated with the presence of diatoms. The shades of light blue result from the occurrence of coccolithophores, phytoplankton organisms that strongly reflect light due to their chalky shells - Source : NASA's Earth Observatory (http:/earthobservatory.nasa.gov)
