At the High Energy Benthic Boundary Layer Experiment (HEBBLE) Site (4820 m depth in the western North Atlantic) periods of strong currents and sediment erosion alternate with periods of weak flow and massive deposition. The authors investigated the impact of this atypical hydrodynamic environment on the isopod fauna by testing for a difference in composition between the HEBBLE Site and a tranquil location, the Deep Ocean Mining Environmental Study (DOMES) Site A (ca. 500 m) in the Equatorial Pacific. Epifaunal isopods were significantly less abundant at the HEBBLE Site than at the comparison site despite significantly greater total isopod numbers at the HEBBLE Site. The authors suggest that the hydrodynamic regime puts epifaunal isopods at risk, making them rare at the HEBBLE Site.