This satellite image from the Coastal Zone Color Scanner represents average conditions over several years. It shows the concentration of chlorophyll in the upper layer of the ocean, with higher amounts indicated by the warmer colors. Chlorophyll is produced by phytoplankton, the lowest level of the food web in the marine ecosystem. Phytoplankton "bloom" in the cold, nutrient-rich water that rises from the deep ocean into the sunlight, where photosynthesis can take place. (Image courtesy of Gene Carl Feldman, NASA, Goddard Space Flight Center.)

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