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Factors that promote the introduction and establishment of non-indigenous species (NIS) within port environments are not completely understood. In the present work the structure of fouling community was studied in three Northern Tyrrhenian port systems (Western Mediterranean), focusing on the relationships between fouling structure components and the associated macrofauna, considering whole communities and NIS assemblages. For each port system, fouling samples from two harbour types (large port and recreational marina) were collected and, within each large port, we considered two use destinations (commercial and touristic). Results showed that harbour type and use destination shaped the structure of sessile fouling differently, with their relative influence varying among port systems. Highly positive relationships were detected between macrofaunal sessile taxa and associated organisms for both whole communities and NIS assemblages. Possibly due to their complex three-dimensional morphology, erected bryozoans and serpulid tubes showed marked association with the majority of vagile taxa, especially NIS. These results suggest that high levels of spatial complexity of fouling basibionts could promote the invasion success within port environments. [Display omitted] • Fouling structure components were studied in Mediterranean port environments. • A high spatial heterogeneity of fouling structure components was observed. • Harbour type/use destination shapes fouling structure components assemblages. • The complex physical structure of sessile organisms promotes NIS establishment. [ABSTRACT FROM AUTHOR]

Facilitation cascades are increasingly recognized as key drivers of biodiversity in a variety of habitats, yet their temporal variability remains poorly investigated. On shallow subtidal rocky reefs, positive interactions between the canopy-forming species, Halopithys incurva , and its epiphyte, Jania rubens , enhance the abundance and diversity of the associated mobile invertebrate assemblage. By means of a field experiment manipulating the presence of J. rubens on H. incurva plants, we investigated whether the effects of this facilitation cascade varied over time scales of months. Despite seasonal fluctuations in its biomass, J. rubens enhanced total invertebrate abundance and species richness by 64% and 45%, respectively, throughout the experiment. Our results suggest that the presence of J. rubens , likely by providing novel microhabitats and increasing resource availability, sustains invertebrate biodiversity of shallow macroalgal forests consistently between warm and cold periods. Understanding the temporal dynamics of facilitation cascades and their mechanisms can help inform management strategies targeting biodiversity conservation and restoration under current and future climates. [Display omitted] • The temporal dynamic of a facilitation cascade was tested in a shallow rocky reef. • Positive effects of a subtidal macroalga and its epiphyte on mobile invertebrates. • Seasonal variations in epiphyte biomass did not affect the facilitation cascade. • The presence of the epiphyte sustains patterns of biodiversity over time. [ABSTRACT FROM AUTHOR]