Marine environmental monitoring is essential to ensure that heavy-metal (HM) concentrations remain within safe limits. Most seawater analyses currently consider sediment or water samples, but this approach does not apply to rocky substrates, where water samples can only indicate immediate contamination. We used two common Mediterranean algae species, Cystoseira compressa and Ericaria mediterranea, as bioindicators living in the intertidal zone on rocky substrates along the seacoast. HM concentrations were assessed over a one-year period in the perennial base crust and in the seasonal frond, considering marine sites characterised by different contamination risks. Both algae showed that HMs accumulate mainly in the perennial base rather than in the seasonal frond. Furthermore, the algae species always showed a different order of bioaccumulation factors: Cd > Ni > Pb > Cr > Cu > Mn > Zn for the frond and Pb > Cr > Ni > Cd > Mn > Cu > Zn for the base. Our study shows that C. compressa and E. mediterranea accumulate HM consistently with the types of sites analysed and differentially with respect to the part of the thallus. These results demonstrate that these algae can be effectively used as reliable bioindicators to assess the presence of HM in marine environments with rocky substrates, providing both short- and long-term monitoring.

This study aimed to expand knowledge on the distribution and biodiversity of the genus Padina in Sicily and in the Mediterranean Sea. Thanks to the studies of samples collected along the Sicilian coast and the re-examination of herbarium specimens labelled as Padina pavonica, we reported the following five species in Sicily: P. ditristromatica, P. gymnospora, P. pavonica, P. pavonicoides and P. tetrastromatica. Particularly, we documented the first supported occurrence of P. gymnospora in the Mediterranean Sea and the first finding of P. pavonicoides and P. tetrastromatica along the Italian coast. Furthermore, a new key was created for the identification of all species belonging to the genus Padina present in the Mediterranean Sea today.

Nowadays species belonging to the green algal family Characeae are highly endangered. For this reason, many of them are protected by European directives and included in Red Lists. In Italy, however, the Red List of Characeae does not exist and the distribution of these species is often unknown, especially in Sicily wetlands. In this study, we investigated the distribution and morphology of Characeae in fresh and brackish water wetlands, both natural and artificial, located in various areas of eastern Sicily (Italy). During the survey Chara globularis Thuiller, Chara vulgaris Linnaeus, Nitella capillaris (Krocker) J.Groves & Bullock-Webster, and Tolypella glomerata (Desvaux) Leonhardi were found. This is the first record of these species in the investigated sites. The results improved the knowledge of freshwater algal biodiversity in Sicily and, above all, allowed to fill distribution gaps of the Characeae species, to apply adequate protection measures and create national Red Lists of Characeae.

Cystoseira sensu lato (s.l.) (Fucales, Phaeophyceae) form structurally complex marine forests along the warm-temperate coasts of the Mediterranean Sea and the eastern Atlantic Ocean. They are experiencing widespread decline, yet their conservation and restoration are hindered by taxonomic uncertainty. Within Cystoseira sensu stricto (s.s.), species boundaries among taxa traditionally referred to as C. compressa, C. foeniculacea, C. humilis (including the C. canariensis morphotype), and C. pustulata have long been debated due to the high plasticity and partial overlap of diagnostic morphological traits. Here we reassess species boundaries within the Cystoseira s.s. complex using an integrative approach combining morphology, ecology, and multilocus genetic data. We collected specimens from 20 sites spanning the Mediterranean–Atlantic distribution. Genomic DNA was extracted from 220 specimens and Sanger sequencing generated 243 new sequences (ITS2: n = 99; cox1: n = 88; rbcL–rbcS: n = 56). We inferred single-locus and concatenated phylogenies, reconstructed haplotype networks, and applied multiple single-locus species delimitation approaches to test the robustness of inferred boundaries. We consistently recovered two primary lineages corresponding to C. foeniculacea and a C. compressa complex, the latter including specimens historically identified as C. pustulata and the C. humilis with the C. canariensis morphotype. Within an integrative framework that prioritises cross-locus concordance and diagnosability, we recognise two species-level lineages in Cystoseira s.s. and treat the morpho-ecologically coherent entities within C. compressa at the variety rank. Accordingly, we propose the new status and combination Cystoseira compressa var. pustulata (Ercegović) D’Ambros Burchio & Falace, comb. et stat. nov.

In this study, through morphological and molecular analysis approaches, we documented the presence of the typical stage (adult stage) of Penicillus capitatus during the coldest seasons of the year, typically periods when this form had never been reported in the Mediterranean. Indeed, the typical stage is common throughout the year in the western Atlantic (native range of the species), whereas it is rare in the Mediterranean, where the Espera stage (juvenile stage) is the main stage. To date, in the Mediterranean, the adult stage has been found only in the warmer months of the year. Therefore, the observation of the typical stage in the Mediterranean Sea during the cold season might suggest a general increase in the seawater temperature in this basin, rendering this stage of P. capitatus a potential climate bioindicator. Furthermore, owing to the molecular analysis methods adopted, it was possible to assess the relationships between the Mediterranean and Atlantic populations of this species.

Freshwater red algae belonging to the family Batrachospermaceae (Rhodophyta) are poorly investigated, particularly in Italy and in Sicily, where little is known about their distribution along rivers. The present study reports, for the first time, the occurrence of Lemanea fucina Bory in Italy and Paralemanea catenata (Kützing) Vis & Sheath in Sicily. L. fucina formed stalked, highly branched thalli and was characterised by an internal structure lacking a cortex around the central axis cell, T-shaped ray cells, and spermatangial papillae arranged in circular patches at the nodes. In contrast, P. catenata showed unstalked, unbranched to pseudobranched thalli arising from a basal crust and was characterised by a central axis composed of numerous cortical filaments and radial cells arranged in two layers: a proximal layer not reaching the outer cortex and a distal Y-shaped layer attached to the cortex, with nodal spermatangial sori arranged in rings. Both species were recorded along the Alcantara River, one of the main rivers in eastern Sicily. Information on the morphological and ecological characteristics of the two species is presented.