Macrofauna associated with intertidal mussel beds in the Knysna estuarine embayment, South Africa

Effects of habitat homogenisation on assemblages associated with mussel clumps

“…It is a gregarious species that attaches to hard substrates using byssal threads and establishes dense clumps or beds on exposed or moderately exposed temperate rocky shores, such as in the northwest portion of the Iberian Peninsula, where temperature and food supply are optimal for the species [ 14 ]. In areas where mussel species are dominant, they can prevent the attachment of other sessile organisms by competing for primary substratum [ 9 , 12 ]. However, mussels, as ecosystem engineers [ 15 , 16 ], modify the local environment and provide secondary substratum and structurally complex three-dimensional habitat for many species [e.g., 9 – 12 , 17 , 18 ].…”

“…In areas where mussel species are dominant, they can prevent the attachment of other sessile organisms by competing for primary substratum [ 9 , 12 ]. However, mussels, as ecosystem engineers [ 15 , 16 ], modify the local environment and provide secondary substratum and structurally complex three-dimensional habitat for many species [e.g., 9 – 12 , 17 , 18 ]. Consequently, the habitat provided by shells of live and dead mussels and the interlacing byssal threads ameliorates physical and physiological stress and provides protection against removal by predators or dislodging by waves [ 15 ].…”

“…Although it is widely recognized that mussel beds increase diversity [e.g., 9 – 12 , 17 , 18 ], the drivers shaping these assemblages are poorly explored [ 10 , 17 ]. Additionally, studies that have assessed the relationship between mussel population structure (i.e., density, size and age) and abundance, composition or diversity of mussel-associated assemblages have shown contrasting results [ 22 ].…”

“…Additionally, studies that have assessed the relationship between mussel population structure (i.e., density, size and age) and abundance, composition or diversity of mussel-associated assemblages have shown contrasting results [ 22 ]. Some works [e.g., 12 , 13 , 23 ] reported a negative relationship between mussel abundance and diversity of assemblages, whereas others have found a positive relationship between mussel abundance and the number of species and abundance of fauna [ 24 ] or no relationship at all [ 22 ]. On the other hand, Hammond [ 25 ] and Hodgson et al [ 12 ] showed that there was no relationship between mussel size and species richness and diversity, whereas Cole and McQuaid [ 24 ] found a negative relationship between mussel size and the number of species and the abundance of fauna.…”

“…Some works [e.g., 12 , 13 , 23 ] reported a negative relationship between mussel abundance and diversity of assemblages, whereas others have found a positive relationship between mussel abundance and the number of species and abundance of fauna [ 24 ] or no relationship at all [ 22 ]. On the other hand, Hammond [ 25 ] and Hodgson et al [ 12 ] showed that there was no relationship between mussel size and species richness and diversity, whereas Cole and McQuaid [ 24 ] found a negative relationship between mussel size and the number of species and the abundance of fauna. However, a higher diversity was found among larger but older mussels [ 26 ], thus being unable to separate age and size effects [ 17 ].…”