In deeper channels with sloped edges, zonation may create a littoral or edge habitat. In shallow channels or low water conditions, the streambed can be exposed intermittently. The streambed can comprise a variety of physical and organic materials and can be either an eroding basin or a depositional environment. These situations can alternate in the same stream, as may be seen in riffles or ponds. In slow-moving streams, there is an abundance of invertebrates, especially aquatic insects.
Vegetation is generally absent from the bottom habitat, except along the stream bank.
In fast-moving streams, algae, mosses and liverworts and some specially adapted flowering plants can adhere to rock surfaces or root firmly in the gravel bottom. Aquatic animals are also well adapted to withstand fast current and seasonal variations in water level.