phytobenthos

thumb|upright=1.2|Cyanobacteria|Filamentous cyanobacteria growing on an underwater surface

Phytobenthos () (from Greek (phyton, meaning "plants") and (benthos, meaning "depths") are autotrophic organisms found attached to bottom surfaces of aquatic environments, such as rocks, sediments, or even other organisms. This photosynthetic community includes single-celled or filamentous cyanobacteria, microalgae, and macrophytes. Phytobenthos are highly diverse, and can be found in freshwater and marine environments, as well as transitional water systems. However, their distribution and availability still depend on the factors and stressors that exist in the environment. Because phytobenthos are autotrophs, they need to be able to subsist where it is still possible to perform photosynthesis. Similar to phytoplankton, phytobenthos contribute to the aquatic food web for grazers and heterotrophic bacteria, and researchers have also been studying their health as an indicator for water quality and environmental integrity of aquatic ecosystems.