Ecosystem assessment of the environmental impact of light pollution and urbanisation on Mediterranean coastal habitats

Artificial light at night (ALAN) is a growing ecological issue in coastal ecosystems, disrupting natural light-dark cycles that regulate species behavior, physiology, and interactions. While well studied in terrestrial systems, ALAN effects on marine coastal ecosystems are less understood. This PhD thesis addresses this gap by examining how ALAN alters species behavior and benthic community structure across different habitat types. It begins with a systematic review of ALAN impacts in intertidal and shallow subtidal hard-bottom habitats, highlighting the need for more in situ studies due to the creation of habitat-specific light-shadow mosaics. A field experiments on a rocky shore in Tuscany assessed locomotion of Paracentrotus lividus under ALAN, showing altered movement only under full moonlight. In the same area, a pilot study using ecoacoustic monitoring reveals how ALAN changes benthic soundscapes, offering a non-invasive method to detect invertebrate activity under ALAN. I then analyzed how ALAN affects the trophic ecology of the crab Pachygrapsus marmoratus using stable isotopes, finding shifts in niche width and trophic position. Lastly, I compared epifaunal and macroalgal assemblages in lit and unlit natural and artificial habitats, showing that ALAN interaction with artificial structures alters community composition. Overall, this thesis reveals species- and habitat-specific ALAN effects and emphasizes the role of structural complexity in shaping ecological responses.