Fucalean algal forests in the Mediterranean Sea: current status and challenges for restoration

Fucalean brown algae of the genera Carpodesmia, Cystoseira and Treptacantha are a typical feature of shallow subtidal Mediterranean habitats, where these habitat-forming seaweeds produce canopies playing a key role in the functioning of coastal ecosystems. In recent decades these communities have undergone a major decline in cover and biomass; this has generated increasing interest towards their conservation and restoration. Recent modelling studies based on distribution data for 20 species showed that fucalean canopies are currently present along the Mediterranean coastline for 6,342.41 km out of a total coastal length of 46,000 km. Topographic coastal slope and nature of substrate were shown to be the main factors controlling their distribution. Factors considered proxies of human impact, such as the distance from ports and urban areas, were also identified as important, confirming the negative effects of pollution and urbanization on these communities. Recent restoration initiatives have utilized recruitment enhancement methods by ex situ and in situ techniques based on production of juvenile specimens in the laboratory and in the field, respectively. Successful reforestation at local scale was obtained for Carpodesmia amentacea in northern Italy, Treptacantha barbata in the Balearic Islands and Treptacantha elegans in Catalonia. These trials indicated also that heavy grazing and destructive storms represent major challenges for these projects. We conclude that large scale restoration is possible, but requires baseline information with an in-depth knowledge of the species ecology and of the areas to be restored, together with the development of cultivation protocols to make consistently efficient restoration interventions.