This paper evaluates the effect of the tube-building, habitat structuring polychaete Lanice conchilega on the macrobenthic community and sediment characteristics of its habitat. To investigate which factors make species occur in a well-known bio-engineered habitat, macrofaunal and sedimentological data, gathered over a period of 10 years in a shallow, fine sediment bottom of the Belgian Part of the North Sea, were submitted to analyses. Both sediment composition and community structure of the associated macrofaunal matrix were affected by the presence of L. conchilega. The effect of the protruding tubes on hydrodynamics clearly resulted in the retention of fine sediment particles, while the increased coarse fraction was assumed to reflect a dynamic population build-up. This study confirmed that tube aggregations of L. conchilega expand the realized niche of several species without forming their own association. A species rank list was created according to each species' association with L. conchilega. This species rank list is extensively discussed based on all ecological knowledge available. Species are favoured by the habitat modifying ability of the polychaete tubes, which create and regulate refuge for species, alter the interactions between local species and change the physical factors of the environment. This descriptive and correlative data study examines the ecological importance of the bio-engineer L. conchilega on species level. (C) 2007 Elsevier Ltd. All rights reserved.