Reehab (biogenic reefs)

The REEHAB project is studying the geographical distribution of Sabellaria alveolata,the
honeycomb worm, and the effect of various environmental factors on its habitat. Run by Ifremer and funded by the Total Foundation, the REEHAB project involves three international scientific partners: the University of Porto (Portugal), Bangor University (Wales) and Plymouth University (England).

The honeycomb worm is a sessile marine tube worm, living in a tube that it builds from sandy sediments, cementing them together with an organic glue that it secretes. At low tide, the worm stays in its tube, protected by a plug of mud. When the tide comes back in, it emerges out the top of the tube and deploys its feeding tentacles to trap the microalgae that it feeds on. The presence of honeycomb worm tubes often goes unnoticed; the tubes generally do not exceed more than a few centimetres. However, in some circumstances, they fuse together and form veritable reefs up to 2 m thick that can stretch over several square kilometres.

Honeycomb worm reefs harbour a broad range of microfauna that colonize the hollows of the reefs. Many species come to feed or find shelter. These marine annelids are filter-feeders, filtering water to extract their food. The high density of individuals –sometimes more than 30,000 individuals per m² – means that these reefs are biological filters that actively contribute to the functioning of the bays in which they develop.

Sabellaria alveolata is found from Scotland to Morocco. The highest densities are found on the French and English coasts, particularly in the English Channel and on the Atlantic coast.Thanks to the partners present in different European countries, visits to the sites will help draw an accurate map of the current species distribution, from southern Portugal to Scotland. This information will, for example, help marine diversity managers define marine protected areas.

The project also aims to observe variation in the Sabellaria alveolata bioconstructions and assess the health status of the worms. To learn more about this project visit the official webpage at honeycombworms.