Does Habitat Structure Really Affects Macroinfaunal Benthic Assemblages?

Generally, environments that present greater range of structural components can support greater numbers of species and larger abundances of organisms. However, mechanisms behind this effect are not entirely clear and some studies did not observe positive effects of complexity on diversity and abundance of biological assemblages. In this study, it was asked whether abundance and diversity of macrobenthic assemblages of soft bottom are influenced by variation of two traits of habitat structure, the number and evenness of structural elements. Despite differences found, positive relationship between habitat structure traits and richness and abundance of benthic macrofauna were not observed. For both traits, a greater number of specimens of Bispira sp. and Terebellides sp were observed in more complex systems. These taxa were favored by the presence of non-natural gravels and their larvae were recruited from the water column, possibly coming from adjacent habitats. Benthic macrofauna of soft bottoms were significantly influenced by habitat complexity and, considering high taxonomic and morphological diversity, indicate that multivariate analyses were more appropriated to investigate such complex effects. Future work should address different combinations of structural traits and mechanisms behind the effects.