| Zusammenfassung: | Abstract Benthic algae were used to identify reference conditions of springs for bioassessment purposes. Benthic algae and environmental factors were quantified in 70 springs (nonthermal andmostly near-natural) in the southeastern Alps. Spring types were identified by fuzzy clustering of nondiatom, benthic algal assemblages. Canonical Correspondence Analysis (CCA) andindicator species analysis (IndVal) were used to identify the most relevant environmental determinants of taxonomic composition in springs and to characterize the ecological traitsof key taxa. A total of 120 macro- and microscopic benthic pro- and eukaryotic algae (excluding diatoms) were identified. Cyanobacteria (especially Chroococcales andOscillatoriales) were strongly prevalent. Seven spring types were identified by fuzzy clustering of nondiatom, benthic algal assemblages. IndVal identified 22 taxa that weresignificant indicators of spring type, and fuzzy clustering based on environmental preferences identified 18 other important taxa associated with spring type. Spring types differedin environmental features, species richness, and diversity. Mid-to-high altitude, oligotrophic, carbonate flowing springs (rheocrenes) with medium conductivity were the most commonspring type and were characterized by shade-tolerant (Chroococcales) or rheophilic (Tapinothrix varians) cyanobacteria. Low-altitude, shaded, and slightlyNO3-N-enriched carbonate rheocrenes with medium-to-high conductivity supported rheophilic or eutraphentic cyanobacteria and red algae. Siliceous rheocrenes hadbenthic algal assemblages dominated by soft-water, rheophilic cyanobacteria and by the rheobiontic chrysophyte, Hydrurus foetidus. Mostly siliceous seepages andpool springs supported predominantly chlorophytes, especially filamentous Zygnematales. Xerotolerant cyanobacteria were common on carbonate rock-face seepages. Tufa springs werecharacterized by cyanobacteria and by the desmid, Oocardium stratum. In iron springs, benthic algae (mainly filamentous green algae and xanthophytes) were poorlydeveloped, whereas iron bacteria were common. The most influential factors were pH and conductivity, shading, NO3-N, temperature, current velocity, and substratumparticle size. The spring types identified may prove useful as references for assessments of ecological integrity naturalness value, at least for the Alps ecoregion.
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