Bioengineering promotes habitat heterogeneity and biodiversity on mussel reefs

Loss of biodiversity is among the most pressing global problems. Yet, despite its pertinent nature, the biological processes involved in the maintenance of biodiversity are poorly understood. Habitat heterogeneity is widely regarded as a key factor underpinning the biodiversity of land- and sea-scapes. However, it remains unclear how species coexist in many of those ecosystems that lack conspicuous heterogeneity. We demonstrate how spatially self-organized mussel reefs create microhabitats/heterogeneity that facilitate diverse invertebrate communities. By comparing seawater filled pools with open inlets in a mussel reef, we found that natural reef pools, emerging due to the habitat engineering of the mussels, strongly increased variation in organic enrichment and promoted beta-diversity compared to the surrounding tidal flat. These findings significantly extend the scale of influence typically described for self-organized habitats and highlight the importance of bioengineering and its positive effects on habitat heterogeneity and community diversity.