The seasonal evolution of the chlorophyll a concentration as seen by a « water color » satellite (SeaWifs) in the Atlantic Ocean.
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)
Rosette used to collect seawater samples during a scientific cruise in the South Pacific Ocean. Duringthe austral summer,the amount of chlorophyllais so low thatthe water becomesdeepblue,almostpurple. (Photo : Joséphine Ras)
