Phytoplankton bloom in spring when sunlight hits the water. The green color is from chlorophyll, the pigment needed for photosynthesis. The blue color is from the reflective plating around coccolithophores, a type of phytoplankton. The Chatham Rise is an underwater plateau that causes deep water to rise, bringing up nutrients. The feature is located where cold Antarctic currents meet warmer, subtropical water. The mixing of water and the nutrients foster large phytoplankton blooms.
Phytoplankton are the base of the marine food web and so they are food to nearly all other marine organisms. By using carbon dioxide for photosynthesis, phytoplankton help to reduce the buildup of greenhouse gases in the atmosphere.
Courtesy of Norman Kuring/NASA's Earth Observatory. earthobservatory.nasa.gov/IOTD/view.php?id=42099. Public Domain.