Rotifera are known to inhabit the sediment surface of running waters for a long time and many studies have found a high species richness. Benthic rotifers are among the most speciose taxa, and they occur both at the surface and within the bed sediments (hyporheic zone) at densities higher than other meiofauna.
Because they are small and difficult to identify, rotifers have not been explored thoroughly in stream ecology. But their ability to disperse rapidly, their short-generation times, and high species richness in streams however makes them useful assemblages in which to study ecological theory.
The great majority of species present in river sediment surfaces and deeper layers (or associated with mosses) correspond to Bdelloidea. The class Monogononta is represented mostly by the families Proalidae, Notommatidae (genus Cephalodella, Notommata) Dicranophoridae (genus Encentrum, Dicranophorus), Colurellidae (genus Lepadella).