In bed with Mytilus spp: Meta-community dynamics within fragmented mussel beds

Metacommunity dynamics in engineered habitats provide challenges of both applied and fundamental importance. In order to address this general problem, we investigated spatial interactions among communities associated with intertidal patches of Mytilid mussels in the St. Lawrence estuary (Quebec). Experimental mussel patches (400 cm² cages) were transplanted adjacent to and distant from resident mussel beds on 12 field sites (24m²) exhibiting 40 to 60 % fragmented mussel cover. Cages were sampled at 3 and 12 weeks intervals from August to November and all colonizers were identified to the species level. Additional experiments were conducted to control for biotic and abiotic effects of mussels on associated fauna, as well as for effects of resident patch density and geometry at the experimental patch and site levels. Results reveal important spatiotemporal variability in the structure of benthic communities associated with mussel beds. They further show how both patch connectivity across spatial scales and temporal patterns of connectivity influence the degree of variation in community structure as well as seasonal patterns of species richness and abundance. Given the dynamic nature of mussel beds in intertidal systems, our results suggest that mussel beds and their associated fauna may be understood as metacommunities where habitat parameters such as connectivity and habitat size have dynamic rather than static properties.