MEPS 351:163-175 (2007)  -  DOI: https://doi.org/10.3354/meps07033

ABSTRACT: Habitat-modifying species such as Mytilus edulis strongly impact both community structure and ecosystem functioning through positive or negative interactions with other species and by changing physical and biological conditions. A study of natural patches of mussels showed that C and N content of sediment was higher in mussel patches compared to the surrounding sand community. Species richness and biomass of associated macrofauna and -flora was enhanced even by the presence of single mussels and increased rapidly with patch size up to about 150 cm², while no change in sediment meiofauna was found. In order to separate the effects of structure and function of M. edulis, a manipulative field experiment was performed with constructed patches of cleaned live mussels or intact empty shells. After 3 mo colonisation, the number of associated species in both treatments approached those in natural mussel patches, indicating that species richness was mainly due to physical structure. Abundance and biomass of associated flora and fauna were higher if live mussels were present because mussel biodeposition and nutrient regeneration supplied limiting resources and increased carrying capacity. Species composition was also affected. Complexity and biodiversity increased with time, especially if Fucus vesiculosus plants established themselves. Measurements of community metabolism showed that the associated community found in mussel patches depends on mussel biodeposition for 24 to 31% of its energy demand. Thus, the energy balance of the community is dependent on the function of live mussels.

KEY WORDS: Biodiversity · Ecosystem functioning · Facilitation · Species interactions · Habitat modification · Mytilus edulis · Community metabolism