Benthic algae are algae that grow on the bottom sediments of a waterbody. Benthic algae are most commonly filamentous or colonial forms, but also may be microscopic single-celled organisms.

Benthic algae perform various beneficial functions in waterbodies, but may also be troublesome. Several examples of problems associated with benthic algae are described below:

• Benthic algal growth can snag anglers' fishing gear.
  
• Dense benthic growth can break free of the bottom and float to the surface.
  
• Large rafts of free-floating algae may form obstructive mats that can accumulate along shorelines.
  
• Offensive odors can be produced when benthic algae mats decompose.
  

The Role of Benthic Algae in Waterbodies
Benthic algae provide food and habitat for many aquatic organisms. In this way they contribute to the biological productivity of aquatic systems.

Health Concerns:
Benthic algae generally do not pose a known direct threat to human health.