Résumé: Invasive species are able to deeply alter coastal marine ecosystems ranging them among the most influential global changes of the present time. In the context of spatio-temporal variability, temporal trajectories of invasion impacts are very poorly known processes. The aim of the present study was to examine the impact of the invasive Caulerpa racemosa var. cylindracea (Chlorophyta) on benthic macrophyte assemblages in the north-western Mediterranean Sea (Marseille, France). A comparison was made between two different months (March versus November) and between years (2002/2003 versus 2006/2007). The results showed that there was significant variability between months and years in the biomass of Caulerpa as well as in its impact on macrophyte assemblages. In addition, Caulerpa outcompeted other invasive species, such as Asparagopsis armata and Womersleyella setacea, which showed strongly reduced biomass in invaded compared with non-invaded patches.