Distribution of macroalgae in the area of Calvi (Corsica).

The project, while providing some interesting insights on using a ROV as a tool to study marine biodiversity, generated a dataset for the distribution of 19 macroalgae on both standardised and new transects in the Bay of Calvi (Katz et al. 2021). The observed species of macroalgae included: Acetabulariaacetabulum, Amphiroarigida, Caulerpaprolifera, Caulerpacylindracea, Codiumbursa, Colpomeniasinuosa, Corallinales (order), Cystoseirabrachycarpa, Cystoseiracrinita, Cystoseiraspinosa, Cystoseirazosteroides, Dictyota (genus), Flabelliapetiolata, Halopteris (genus), Halopterisscoparia, Jania (genus), Osmundariavolubilis, Padina pavonica and Peyssonneliasquamaria.The videos also showed that the invasive algae Caulerpacylindracea has spread between 2016 and 2019 and that more focused studies should be held in the Bay to assess the actual reach and possible impacts of this invasion.Finally, our ROV video transects have also underlined the significant presence of particular benthic macroalgae communities over habitat zones described as "soft-bottom" on benthic habitat maps. Although the biomass per unit area of these communities is probably lower than for most coastal rocky bottoms, this widely-spread habitat type holds a contribution to primary production to be considered in coastal ecosystem models.