The hidden biodiversity of diatoms (Bacillariophyceae) of Stara planina Mountain waterfalls (Serbia)

Abstract

Through a combination of biotic and abiotic environmental factors, waterfalls create unique habitats supporting species diversity. Thanks to their adaptable characteristics, diatoms are well-adjusted to life in wet microhabitats of waterfalls such as rock, stone, gravel, or mosses. This research aimed to assess the epiphytic and epilithic diatom compositions, ecological groups, and Shannon's diversity index in five waterfalls of Stara planina Mountain. In 2019 and 2021, the study revealed diverse diatom flora, with the highest diversity in the Bigar Waterfall (99 taxa). Dominant genera such as Eunotia, Gomphonema, Navicula, and Nitzschia were recorded. Among the 189 identified taxa, 18 are new to Serbia's diatom flora, including the first European documentation of Hannaea yalaensis. According to ecological groups, water in the investigated waterfalls was oxygen-rich, neutral to alkaline, and oligo to ß-mesosaprobic. Generally, the diatom communities in the examined waterfalls were oligohalophobic, aquatic to aerophilic, and sensitive or tolerant N-autotrophic.