Diatom Biodiversity of springs in the Berchtesgaden national park (North-eastern Alps, Germany), with the ecological and morphological characterizaion of two species new to science

Diatom assemblages were investigated in 9 springs of the Berchtesgaden National Park (carbonate substratum; north-eastern Alps, Germany), by collecting individual samples from the main substrata (stones, bryophytes, surface sediment), and measuring an extensive number of environmental variables. Overall, 104 taxa belonging to 39 genera were found. The highest number of taxa observed in any one sample was 37. The Shannon-Wiener Diversity Index varied between 1.2 and 2.4. The most frequent (counted in 2 4 samples) and abundant (maximum relative abundance > 5%) species were Achnanthidium minutissimum, Meridion circulare, Diatoma mesodon, Eucocconeis laevis, Navicula leistikowii, Denticula tenuis, Encyonema sublangebertalotii sp. nov., Planothidium lanceolatum, Achnanthidum pyrenaicum, Eunotia arcubus, Navicula cataracta-rheni, Rossithidium petersenii, Achnanthidum dolomiticum, Diploneis krammeri, Navicula ciyptotenella, and Reimeria sinuata. The proportion of species belonging to one of the threat categories of the Red List for central Europe was 54%, and included species belonging to category 3 ( "Endangered"): Eucocconeis jlexella, Navicula moenoj?anconica, N. wildii, and Rossithidium petersenii. Two species new two science were discovered and described; one species was transferred to the genus Sellaphora (S. perhibita comb. nov.), and its ultrastructure was documented in detail. Encyonema sublangebertalotii sp. nov. resembles widely distributed species such as E. minutum and E. lange-bertalotii from which it can be distinguished by the outline (in particular the endings), dimensions, external raphe course and areolae density. Moreover, it appears to be mainly epiphytic in oligo(meso)trophic springs. Oligotrophic conditions might be important also for the second new species, Eunotia glacialispinosa sp. nov. which can be easily distinguished from similar species by its dimensions, striae and areolae density, distal raphe course, and by the presence of the characteristic spines. In Berchtesgaden it occurred exclusively in a specific spring type (seepages), and was found to develop also in comparable habitats (e.g. small dystrophic lake in a fen) by examining materials from several countries in the North of Europe. All these habitats had slightly alkaline or acidic pH but never presented ombrotrophic conditions. The comparison with a carbonate National Park located at the southern margin of the Alps (Dolomiti Bellunesi) revealed many similarities but also interesting differences mostly linked to the geographic distribution of specific spring types.