Structural and functional effects of Mytilus edulis on diversity of associated species and ecosystem functioning

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 cm 2 , 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.

Distributional overlap rather than habitat differentiation characterizes co-occurrence of bivalves in intertidal soft sediment systems

“…Alternatively, the preference for fine-grained sediments might indicate a favourable habitat, e.g. due to higher food concentrations (Lopez & Levinton 1987), or due to species working their own environment and creating positive feedback loops that provide food and create habitat space for other species (Bertness & Leonard 1997, Bruno et al 2003, Coco et al 2006; single bivalve species can have a positive effect on species diversity in a patch (Norling & Kautsky 2007). Finally, this emergent pattern could reflect mediated effects, i.e.…”

Impacts of ocean acidification on marine shelled molluscs

“…Organic matter that escapes assimilation together with organic matter rejected as pseudofaeces forms biodeposits which provide an organic substrate for macro-and/or micro-organisms living on top or within the sediment and therefore have the potential to locally increase biodiversity (e.g. Norling and Kautsky 2007). Through their excretion of ammonium and urea and through the biomineralization of the biodeposits, shelled molluscs significantly affect microbial activities (e.g.…”

Coastal hypoxia and sediment biogeochemistry

“…Many studies have examined the relationship between macrofauna diversity and sediment metabolism or sediment-water exchange fluxes These studies showed that animal-diversity-biogeochemistry relationships are highly complex. They can be linear or non-linear (MermillodBlondin et al, 2005;Norling and Kautsky, 2007), idiosyncratic and depend on the context (Emmerson et al, 2001;Rossi et al, 2008), and vary with species identity, biomass and density (e.g. Aller and Yingst, 1985;Ieno et al, 2006;Waldbusser and Marinelli, 2006;Marinelli and Williams, 2003).…”