Functional diversity of the faunal assemblages associated with Mediterranean mussel (Mytilus galloprovincialis) clumps

Mussel clumps provide a favourable habitat for a wide range of invertebrates which live in the spaces between shells and on their surfaces. Diversity and structure of these assemblages can be described by functional traits – a series of morphological, biochemical, physiological, structural and behavioural characteristics of organisms, which determine how they interact with the environment and with the individuals of the same and other species. The aim of this study was to assess functional diversity and structure of the faunal assemblages associated with wild and farmed populations of Mediterranean mussel Mytilus galloprovincialis Lamarck, 1819. Mussel clumps were sampled in spring and autumn from 3 mussel farms and 3 sites with wild mussel populations, along the coast of Emilia-Romagna region (Italy, northern Adriatic Sea). A total of 147 invertebrate taxa were identified. Life modalities of the five selected life traits (Bioturbation, Body size, Feeding habit, Larval development and Adult mobility) were assigned to each taxon, using fuzzy coding procedure. Overall, the most abundant life modalities were Superficial modifier, Body size 10-50 mm, Suspension/filter feeder, Direct development, and Swimmer. Univariate functional diversity indices were calculated. Functional richness and Functional evenness of the faunal assemblages were not significantly different between wild and farm habitats in the two seasons, while functional distinctness resulted significantly higher in the wild habitat. Functional structure of the faunal assemblages resulted different between seasons, farm and wild habitats and sites. This was due to the different species composition and abundance between habitat types and seasons, and related to the different life cycles of the species, and presumably to the different environmental conditions and anthropogenic disturbances in the two habitats. Results of this research can be considered as a starting point for the further studies regarding functional ecology of mussel beds in the Mediterranean.