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The diatom Stellarima. Photo courtesy of Rebecca Gast, WHOI.
Diatoms, such as this one (named Stellarima) are part of the phytoplankton, single-celled photosynthetic organisms living in water, wherever sunlight penetrates. They are the major food source of the Antarctic ocean ecosystem. There are many types of phytoplankton. Some of the most numerous are the smallest: very tiny bacteria (0.2-1 micrometers). Others large cells such as diatoms have cells 20-50 micrometers in size, and colonies of cells up to 2cm across—the size of a penny. All of them use light energy to produce food, reproduce, and grow. Some of these cells get frozen into the ice pack that forms each fall in Antarctica. When sunshine warms the ocean in the spring, some phytoplankton “bloom,” growing and reproducing rapidly, leading to huge populations that supply food, directly or through krill, for all Antarctic animals.
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