the tiny, aquatic plant and animal organisms that attach to objects in the bed of a body of water, as certain algae or insect larvae living on submerged plant stems and leaves
See periphyton in American Heritage Dictionary 4
(pə-rĭfˈĭ-tŏnˌ)
noun
Sessile organisms, such as algae and small crustaceans, that live attached to surfaces projecting from the bottom of a freshwater aquatic environment.