475 Nova Hedwigia Vol. 93 issue 3–4, 475–507 Stuttgart, November 2011 Article © 2011 J. Cramer in Gebr. Borntraeger Verlagsbuchhandlung, Stuttgart, Germany www.borntraeger-cramer.de DOI: 10.1127/0029-5035/2011/0093-0475 0029-5035/2011/0093-0475 $ 8.25 Diatoms in very-shallow pools of the site of community importance Danta di Cadore Mires (south-eastern Alps), and the potential contribution of these habitats to diatom biodiversity conservation Marco Cantonati 1 , Horst Lange-Bertalot 2 , Fabio Decet 3 and Jacopo Gabrieli 3 1 Museo delle Scienze, Limnology and Phycology Section, Via Calepina 14, I-38122 Trento, Italy; e-mail: cantonati@mtsn.tn.it 2 Institute for Ecology, Evolution, Diversity, University of Frankfurt, Siesmayerstraße 70, and Senckenberg Research Institute, Senckenberganlage 31-33, D-60054 Frankfurt/M., Germany 3 Environmental Protection Agency of Veneto (ARPAV), Laboratory Department of Belluno, Via Tomea 5, I-32100 Belluno, Italy 4 National Council of Research, Institute for the Dynamics of Environmental Processes (IDPA-CNR), Dorsoduro 2137, I-30123 Venice, Italy With 67 figures and 6 tables Cantonati, M., H. Lange-Bertalot, F. Decet & J. Gabrieli (2011): Diatoms in very-shallow pools of the site of community importance Danta di Cadore Mires (south-eastern Alps), and the potential contribution of these habitats to diatom biodiversity conservation. – Nova Hedwigia 93: 475–507. Abstract: Mires are very selective habitats, and the colonisation by specifically adapted organisms makes them very important both for nature conservation and environmental education. They have, however, been threatened by different types of impacts. Our objective was to study diatoms in stations representative of the main typologies in the Site of Community Importance IT3230060 "Danta Mires", also to produce data for a management plan in the frame of a Life Project. Five shallow pools within different mountain mires were sampled in summer 2005 and morphologically and physicochemically characterized. The sampled sites cover a rather wide pH and TDS content gradient with very low nitrate and silica values. Diatoms were found to dominate in terms of numbers of taxa, followed by desmids, cyanoprokaryotes and filamentous green algae. In total, 86 diatom taxa, belonging to 35 genera, were found. As expected for acidic, low-mineralization waters the genera with the highest number of taxa were Eunotia and Pinnularia, followed by Encyonema, Cymbopleura, Gomphonema, and Nitzschia. The most frequent and abundant taxa were: Frustulia crassinervia, Nitzschia acidoclinata, Kobayasiella micropunctata, Encyonema neogracile, Brachysira brebissonii, Nitzschia perminuta, and Encyonema lunatum. Taxa abundant only in one or few sites were: Eunotia paludosa, Staurosira spinarum, Encyonopsis cesatii, and Achnanthidium minutissimum. Several rare taxa of special interest for their distribution and/or rarity could be found (e.g. Chamaepinnularia schauppiana, Cymbopleura incertiformis var. linearis, C. subapiculata, Eunotia lapponica, Microfissurata paludosa). On average,