Heterogeneity rather than size determines faunal colonization of discrete habitat units: a case study with rhodolith-associated macrofauna

Abstract

The role of habitat complexity determining patterns in the richness and abundance of associated fauna has received considerable attention in the ecological literature. High complexity habitat traits (i.e. high heterogeneity and/or size of discrete habitat units) often promote larger abundances of fauna. Sandy and rhodolith sea bottoms are typically interspersed as mosaics within coastal landscapes. The aim of this study was to experimentally assess the effect of two complexity attributes of rhodolith (i.e. their heterogeneity and size) on the abundance and structure of epibenthic assemblages. A colonization experiment was set up, where experimental units containing rhodolith nodules of varying heterogeneity and size were deployed at two adjacent recipient habitats: a sandy bottom and a rhodolith seabed. After one month, the abundance of fauna colonizing the experimental units was similar in both habitats, but the assemblage structure (i.e. composition) notably differed. The hetero-geneity, rather than the size, of rhodolitic nodules influenced patterns of faunal colonization, even though the habitat type where these experimental units were deployed considerably influenced colonization patterns.