High Alpine streams as models for ecological gradients

Because of their location in the same climatic and geographical area, glaci er- and spring-fed streams show similarities in their ecological conditions , but also pronounced differences in respect of physico-chemical characteri stics. According to the steep-gradient nature of high Alpine areas, some of these variables alter at a small temporal and spatial scale, affecting spe cies composition and abundance of the stream fauna:. Comparing the glacier- fed Rotmoosbach and the spring-fed Konigsbach in Otztal (Tyrol) we evaluate community-organizing forces for the benthic fauna and detect adaptations i n the occurring species. In our ongoing study we focus on the benthic bioco enosis in these two streams, primary physical and chemical variables that d etermine aquatic invertebrate distributions, trophic relationships in the a quatic communities, and colonization strategies of some of the dominant spe cies in these streams.