Diatoms are single-celled algae that live in lakes and streams. Their species composition and abundance reflect the water quality and health of their environments. Many states and federal agencies now monitor diatoms to understand the condition of freshwater sources.
This growing database identifies the diatoms that live in North America. It includes several ways to identify diatoms (by shape, genus, and species), abundant photographs taken through the microscope, a glossary, and lots of background information.