Long-term effects of imitation polychaete tubes on benthic fauna:: they anchor Mytilus edulis (L.) banks

Tube-dwelling polychaetes provide habitat structures that potentially affect the composition of the benthic community. This study describes the long-term effects of tubes as a physical structure on the fauna of an intertidal sandflat, based on a field experiment with tubes that mimicked those of the terebellid polychaete Lanice conchilega. Six 1-m(2) plots, each containing 1000 imitation tubes, were set up on an intertidal sandflat off the Eastern Friesian coast (Germany) and sampled annually over 6 years. The imitation tubes had significant effects on the community structure, species diversity and densities of individual species in the plots. In the first year, two opportunistic polychaete species were more abundant in the experimental plots and spat of two bivalves, Mya arenaria and Mytilus edulis, used the imitation tubes as a settlement surface. M. edulis remained attached to the tubes and started to form banks. At the end of the experiment, the size composition of M. edulis was similar to that found in natural banks. The mussels had overgrown the imitation tubes and provided a physical habitat structure themselves. Interannual changes in the community among imitation tubes and tubes with attached mussels reflected changes in the fauna of the surrounding sands. The effects of imitation tubes on the benthic fauna were similar to those of natural L. conchilega tubes, demonstrating that polychaete tubes themselves can be responsible for structuring the benthic community. (C) 2003 Elsevier Science B.V. All rights reserved.