Threatened species of Bacillariophyta

Bacillariophyta are unicellular organisms that are important components of phytoplankton as primary sources of food for zooplankton in both marine and freshwater habitats. Most diatoms are planktonic, but some are bottom dwellers or grow on other algae or plants.

The taxonomy is unclear with different treatments according to author. Some place the class diatoms in the Heterokontophyta, and others in Phytophyta (the larger grouping of algae). Recognizing their single-cell nature, the diatoms are also classified within the Protista.