Are algal communities from near-natural rheocrene springs in the Eastern Alps (Vorarlberg, Austria) useful ecological indicators?
Gesierich, Doris; Kofler, Werner
Spring habitats, nowadays largely used for drinking water supply, are especially vulnerable environments to human-induced disturbances (capturing, water pollutants). Concerning the occurrence and distribution of benthic algae (except diatoms), these environments remain largely underexplored. Therefore we conducted a geographically extended study on these algal communities over a period of 3 years in 23 rheocrene springs and 4 spring streams in the Eastern Alps (Vorarlberg, Austria), covering five out of seven aquatic ecoregions with particular emphasis on the most driving environmental parameters. Altogether 82 taxa were recorded, with cyanobacteria (63) dominating the species spectrum, accompanied by chlorophytes (9), chrysophytes (3), zygnematophytes (4), rhodophytes (2), and xanthophytes (1). Half of the taxa found were visible to the naked eye, with Homoeothrix varians, Phormidium autumnale and Gongrosira incrustans as most frequent and dominant species, occasionally accompanied by Leptolyngbya perforans. The taxa Rivularia periodica, Gloeothece cf. linearis, Scytonema myochrous and the chlorophyte Oedogonium sp. were rare but reached high coverage, especially at sites with specific habitat peculiarities (e.g. higher sulphate concentrations, wet rock habitats, iron spring). About 65 % of the taxa found occurred in less than three spring habitats in varying abundances with 12 taxa (10 cyanobacteria, two chlorophytes) recorded from one site only. Ordination of sites based on their species composition (TWINSPAN) was primarily related to geology / ecoregion and only secondarily related to specific habitat characters. According to multivariate analysis (CCA), distinctions in community structure were mainly related to nutrient concentrations (NO3−, SO42−) and conductivity / altitude (geology related).