A study of the morphology of the brown alga Cystoseira squarrosa De Notaris, a rare and little known species, was carried out on numerous thalli collected at Torre del Serpe near Otranto (Apulia, Italy). Because the original material of this species, held in the Herbarium of the University of Genova (GE), was destroyed during the Second World War, a neotype is designed here. The species is well characterized by the combination of the following characters: not caespitose, bush-like habit; short primary axis bearing 1–2 secondary axes inserted at right angle; oblong and warty tophules; slightly prominent and smooth apex of the axes; robust, rigid, flattened, not spaced spinose appendages with bifid, trifid or multifid apices and conceptacles grouped at the base of the spinose appendages.
The new species Ulva ardreana is here proposed to replace Ulva bifrons, an invalid name because no holotype was designated in the protologue. The new species consists of two to three distromatic blades arising from a short stipe, and it is easily distinguished from the other blade-like Ulva species in having a remarkable diversity in both shape and size of cells in the two layers.
We investigated phytobenthos in submerged marine caves. Underwater caves have rarely been examined for floristic composition. The study was carried out in two Mediterranean marine protected areas (MPAs) [Plemmirio (Maddalena Peninsula, Syracuse, Ionian Sea) and Pelagean Islands (Straits of Sicily)] and the caves were chosen on the basis of their geomorphology, exposure, and bathymetry. From our comparative study of cave floras, we demonstrated that the macroalgal flora of each cave is influenced by the floristic composition of the adjacent area that is a natural source of recruits and by the light environment. Caves that are “visited” (i.e., those situated on one of the underwater routes for scuba divers visiting the MPAs) had floristic richnesses higher than those of “scarcely” or “not visited” ones (i.e., not on tourist routed). This is likely because the visited caves, due to their large entrance and shallow location, have good lighting that favors high macroalgal biodiversity.