hat is a diatom?
Diatoms are aquatic, single-celled algae which possess a hard shell. They thrive in most fresh and salt water environments as long as some moisture is available. In the marine realm, diatoms along with coccolithophorids are the most abundant photosynthetic organisms (since we originally posted this article, bacteria have also been identified as significant phtosynthesizers). Despite their prevalence, they're usually invisible because they're too small to be seen with the naked eye. They're so tiny that hundreds of them can fit on the head of a pin. Diatoms are usually between 2 and 200 microns in diameter. As with many small organisms, what they lack in size, they make up in numbers. During diatom blooms, the waters off California can change color due to sudden population explosions resulting in the growth of many hundreds of thousands of diatom cells per liter of seawater. What a crowd!

Diatoms are considered phytoplankton. The term phytoplankton is used to refer collectively to all photosynthetic organisms that live by floating in seawater. "Phyto" refers to plant and "plankton" refers to a floating lifestyle. Despite their classification as phytoplankton, diatoms are technically not plants since they are single-celled rather than multicellular like plants.