Phytoplankton

Free-floating minute organisms that are photosynthetic. The term is non-taxonomic and refers to a lifestyle (energy utilization and motility), rather than a particular type of organism. Most, but not all, are unicellular ALGAE. Important groups include DIATOMS, DINOFLAGELLATES, CYANOBACTERIA, CHLOROPHYTA, coccolithophorids, cryptomonads, and silicoflagellates.