One of the controlling factors in determining colonisation and survivorship of benthic species is the physical nature of the sediment which, in turn, is regulated by the activities of the resident infauna. This study uses in situ time-lapse sediment profile imagery (t-SPI) to examine the organism-sediment relations of a highly developed benthic assemblage dominated by the ophiuroid Amphiura filiformis. Information related to apparent physical and biological changes in sediment profile structure over two 24 h periods are quantified. Estimates of burrowing capacity, infaunal spatial arrangement, disc chamber formation, feeding mound construction and feeding periodicity for A. filiformis are presented. The use of t-SPI confirmed that A. filiformis is a highly active and dominant member of the infauna, Movie sequences revealed that burrowing and feeding activity greatly influences sediment structure and may mask the bioturbatory activities of other species.