Effect of habitat topography on the structure and diversity of benthic communities across five marinas from the southwestern Atlantic Ocean

Marine urbanization promotes the addition of hard substrata that barely resembles natural substrate nearby. We manipulated habitat topography in five marinas across one of the most populated regions from the Southwestern Atlantic Ocean to describe the effect of habitat complexity on the diversity of benthic communities across sites with distinct conditions and biotas. The highest biomass was found in the two marinas under high pollution and freshwater disturbances, regardless of habitat complexity. Habitat topography did not affect species richness but determined the structure of sessile communities in all marinas. The structure of mobile communities was affected only in the most diverse site, increasing the abundance of isopods. In general, fragile ascidians, hydrozoans, and non-calcified polychaetes dominated complex habitats, while structurally defended animals such as barnacles, serpulids, and encrusting bryozoans dominated simple habitats, suggesting that dominant species are selected by habitat complexity based on their morphological traits. However, the final community structure was also determined by differences across marinas, suggesting that the effect of increasing habitat topography is mostly site-specific. Therefore, strategies to minimize the disparity between natural and artificial habitats must consider historic local community and a multiple stressors scenario.