Effects of non-native turf-forming Rhodophyta on mobile macro-invertebrate assemblages in the north-western Mediterranean Sea

Abstract

The study compared mobile macro-invertebrate assemblages invaded by the two turf-forming invasive macroalgae Womersleyella setacea and Lophocladia lallemandii with non-invaded assemblages. The study was carried out at Pianosa Island, in the Tuscan Archipelago National Park, within the depth ranges where the two invasive species showed high abundance: 35 m depth for Womersleyella setacea and 10 m depth for Lophocladia lallemandii. Results showed significant differences between invaded sites and non-invaded ones for the two turf-forming Rhodophyta. Invaded assemblages showed a lower species richness and a reduction of decapods and molluscs and an increase of polychaetes compared with non-invaded ones. Amphipods showed a drastic reduction in abundance in sites invaded by W. setacea, while they appeared less influenced by the presence of L. lallemandii. Womersleyella setacea showed more severe effects than L. lallemandii, causing deep changes in the structure of assemblages and a reduction of beta diversity of the system.