Cyanoprokaryotes and algae other than diatoms in springs and streams of the Dolomiti Bellunesi National Park (Northern Italy)
Cyanoprokaryotes and algae other than diatoms developing macroscopic life forms and epiphytic on bryophytes were studied in 16 springs (mainly flowing springs, but including two pool springs and an iron spring) and five streams. The high total number of taxa (65) and the low diversity of the individual stations highlight their marked heterogeneity, and the importance of protecting large numbers of springs (including different spring types) to preserve aquatic biodiversity. Only six taxa were found in more than six sites: Tapinothrix varians, Chamaesiphon polonicus, Chlorogloea sp. small cells, Phormidium favosum, Xenotholos kerneri, and Chamaesiphon subglobosus. Epilithon was demonstrated to host assemblages with higher taxa numbers and Shannon-Wiener diversity than epibryon. Epiphytes on bryophytes can be useful additional indicators (e.g. of periodic desiccation), but knowledge on taxonomy and ecology is still insufficient. Multivariate analyses (CCA) allowed to show that the most relevant environmental determinants in explaining the distribution of the taxa were nutrients, hydrological stability, shading, current, and substrate particle size. The sensitivity of the important numbers of species identified to these factors allowed to characterise the main morphological spring types also with this component of the biota. The taxa found included many poorly known taxa which would deserve further study (e.g. Chlorogloea spp.), and rare species which are not frequently encountered in the field or reported in the literature (about 50%, e.g. Ammatoidea normannii, Geitleribactron periphyticum, Tapinothrix bornetii, Tolypothrix pulvinata). The sensitivity to nutrients (and especially to total phosphorus) levels allowed to detect even moderate organic pollution which affected mainly the streams, but also some springs used for drinking by abundant game or cattle. The less pristine situation found in streams, even in a protected area, points to springs as fundamental refugia for the preservation of aquatic biodiversity.