Shellfish reefs such as those formed by the horse mussel (Modiolus modiolus), a large, slow growing species found in the Northern Atlantic, are complex habitats of high conservation value.

A study by Dr. Jose M. Fariñas-Franco with colleagues in the United Kingdom analysed over 40 years worth of data from 100s of dives in 16 horse mussel beds across the species distribution range, from the Irish Sea to Norway. The study reports a biodiversity baseline of  1000 species of marine fauna and macroalgae in horse mussel habitats demonstrating the keystone role of horse mussels as biodiversity hotspots even at low mussel densities. These results, of high importance in the current biodiversity crisis, represent the most comprehensive description of the biodiversity of shellfish reefs worldwide and should be used to designate more meaningful marine protected areas.

The findings are published open access in the journal Science of the Total Environment https://www.sciencedirect.com/science/article/pii/S0048969722081049