Contribution to Charophyceae knowledge in Slovakia - re-discovery of Nitella gracilis.

BACKGROUND: Nitella gracilis (Charophyceae) is a rare charophyte, previously considered regionally extinct in Slovakia. During a systematic survey of charophytes conducted between 2021 and 2025, new localities of this species were discovered. These findings represent the first confirmed records of the species in Slovakia in more than 45 years. The results highlight the importance of small temporary waterbodies such as forest road puddles for the conservation of charophytes. NEW INFORMATION: We found Nitella gracilis in two localities. The first locality was found in a forest pool in the Krupinská planina Mountains, while the second consisted of 23 microsites, located in road puddles near the village of Sklené in the Turčianska kotlina Basin. The water in pools supporting N. gracilis ranged from slightly acidic to slightly alkaline (pH 5.7-7.5) and exhibited relatively low electrical conductivity (21-274 μS/cm). At the second locality, phytosociological relevés were recorded around stands dominated by N. gracilis and classed as the association Nitelletum gracilis. Based on the limited number of confirmed sites, we propose changing its national Red List status from Regionally Extinct (RE) to Endangered (EN (B1, B2a, c)) (IUCN 2012a, IUCN 2012b, IUCN 2024).