Acquired February 9, 2010, this true-color image shows jewel-toned water caused by a phytoplankton bloom off the coast of Argentina. Roughly mimicking the coastline, the bloom forms a giant semicircle in the Atlantic Ocean.
Phytoplankton are tiny plant-like organisms that are the foundation of the ocean food web. Like plants, they contain chlorophyll and other pigments that they use to harvest sunlight for photosynthesis. In northern waters, these organisms are starved for sunlight much of the year, but during the summer months, they explode in colorful blooms such as this one.