How can a satellite hundreds of miles up in the sky take pictures of microscopic plants? It's possible if there are billions and billions of these tiny plants--called phytoplankton--in a particular spot. This is called a phytoplankton bloom. Each plant contains a green pigment called chlorophyll. A big enough phytoplankton bloom, such as one caused by an upwelling, can cause normally blue ocean water to appear green.

SeaWiFS (Sea-viewing Wide Field-of-view Sensor) is attached to a satellite that orbits hundreds of miles (kilometers) above the Earth's surface. SeaWiFS measures the radiance (light intensity) of the ocean water over which it travels. The degree of radiance is affected by the concentration of phytoplankton growing at the ocean's surface. So, by measuring radiance, SeaWiFS can send back information on the concentration of phytoplankton. SeaWiFS images are shown using "false color" to make the concentrations easier to see.



The SeaWiFS image above shows our planet from the view of the SeaWiFS satellite during summer. The green and light blue colors in the ocean show where there is chlorophyll in the water, and the green areas on land show where there is chlorophyll (or vegetation) on land. Can you see the Sahara Desert in Africa? What color is it? What color is the Amazon rain forest?

Scientists at the COOLroom can use SeaWiFS data when we want to know the location of a phytoplankton bloom in the waters off the New Jersey coast. Notice that the image has many different colors besides blue and green. Those "false colors" are based on a scale that shows the concentration of phytoplankton.