Ecosystem engineers can considerably affect the community composition, abundance and species richness of their environment. This study investigates the existence of positive or negative feedbacks of species that compose the community in intertidal biogenic reefs constructed by the ecosystem engineer Lanice conchilega. This tubeworm creates attractive nursery and feeding grounds for the predatory brown shrimp Crangon crangon, while at the same time is preyed upon by C. crangon. The effect of the predation pressure exerted by C. crangon on the bioirrigation and feeding activity of the tubeworm is up until now unknown and it is hypothesised that these activities are affected by the high densities of C. crangon in the reefs. A mesocosm experiment was set up to investigate the effects of predation pressure on the bioirrigation and feeding activity of L. conchilega in the i) absence; ii) restricted presence; and iii) unrestricted presence of C. crangon. Bioirrigation was quantified by the decrease of an artificially introduced bromide (Br−) tracer, while feeding activity was measured from the incorporation of 13C via stable isotope analysis. The bioirrigation rate of the L. conchilega reef equalled about 30 L·m−2·d−1 andwas not affected by the presence of the predator. The food uptake of the tubewormwas however about three times lower in the unrestricted presence of C. crangon, presumably due to the retraction of the worm's body and tentacles in its tube induced by physical contact with the predator. Notwithstanding the impacted food uptake of L. conchilega, the tubeworm maintains its functional role in the presence of predators in soft-bottom intertidal areas.