On Bangia atropurpurea (Bangiales, Rhodophyta), the strictly protected red alga in Serbia

The first observation of the red alga Bangia atropurpurea (Bangiales, Rhodophyta) in Serbia was in 1991 in the Trgoviski Timok River (Eastern Serbia). From 1991 to 2017, the species was sporadically observed at four more locations in three hillmountain rivers in Southwestern (the Gvozdacka River and the Raska River) and Eastern (the Nisava River - two localities) Serbia. More intensive research on this alga was carried out from 2017 to 2020, and a total of 220 localities in 132 hillmountain watercourses were studied. Bangia atropurpurea was recorded at six locations in Southwestern and Eastern Serbia. Five of these locations represent new B. atropurpurea localities in Serbia (the Brusnicka River, the Golijska Moravica River, the Panjica River, the Resava River, and the second locality in the Trgoviski Timok River), while one of them is already known from previous studies (the Raska River). The species was found in running, moderately hard and very hard, well-oxygenated, slightly alkaline waters, mainly low in inorganic nutrients, and in highly variable values of temperature and conductivity. Despite the long period since its first observation in Serbian rivers, the species is still known in a small number of localities. The small number of localities, low relative abundance, and various anthropogenic influences affecting its habitats have led the species to be recognized as endangered and strictly protected in Serbia. The intensive development of small hydropower plants which have emerged in recent years may threaten B. atropurpurea habitats.