Simple flume experiments demonstrate that local flow perturbations by a protruding animal-tube mimic can cause a significant increase in bacterial colonization at the sediment-seawater interface. The occurrence and extent of this increase depend on properties of the viscous sublayer adjoining the bed—specifically, its spatial and temporal continuity, and its thickness relative to tube height. In the field homologous tube effects on bacterial colonization and abundances are likely to be common. These effects are postulated to be important to larval recruitment, community composition, the nutrition of deposit feeders, and sediment dynamics.