Unattached Cystoseira s. l. in the Black Sea: taxonomy of Gongolaria barbata f. repens comb. nov.

Brown algae of the genus Cystoseira s. l. are key species in Mediterranean basin, including Black Sea and Azov. In addition to typical attached forms sensu lato (Ericaria crinita f. bosphorica (Sauvageau) S.S.Sadogurska, J.Neiva et A.Israel, Gongolaria barbata (Stackhouse) Kuntze), an unattached form was previously described for Sea. The taxonomic status this taxon remained uncertain. According results a comparative morphological analysis, it is shown that samples belong barbata. But thalli, collected Dzharylhach Bay seagrass meadows Zostera marina L., have differences. Thalli 30–50 cm long, light brown or yellow-brown; holdfast absent, main axis reduced or, if present, very short thin (2–4 mm). Lateral branches (2–3 mm), smooth; their length 15–30 cm. ultimate filamentous, sometimes with oval-shaped aerocysts, single arranged chains. Receptacles rarely spindle-shaped, 8–12 mm length, without spines, but sterile mucron at end. Therefore, new nomenclature combination proposed: repens (A.D. Zinova & Kalugina) S.S. Sadogurska comb. nov. It concatenata A.D.Zinova Kalugina invalid. addition, not synonymous aurantia Kützing Orellana al. (2019), which authors previouslyrearranged s.s. Analysis phylogenetic trees from works by different showed Atlantic Ocean do clade may be other species.