Long-term changes of alpine stream macroinvertebrates in relation to glacial recession.

Alpine landscapes are being rapidly transformed, being fueled by ongoing environmental change and glacial recession. Glacial recession has caused emergence of new stream channels as well as changes in the physico-chemistry of surface waters embedded in glaciated landscapes. Our research examined temporal changes in the physico-chemistry and macroinvertebrates during (1) the elongation of a glacial stream and (2) among different alpine lake networks (inlets, outlets, and downstream sites) over the last 24/25 years. The glacial stream study revealed rapid colonization of the emergent stream following deglaciation as well as colonization of previous sites by novel taxa (some from lower elevations). The water physico-chemical data revealed changes in the habitat template of sites over the study period, especially in respect to water temperature and turbidity. The lake network study also showed changes in macroinvertebrate assemblages over the observation period as well as differences on the basis of lake location and type. Here, lake outlet water temperatures increased more over time at northern than southern Alpine lakes. Further, kryal and rhithral lake outlets differed in response regarding water physico-chemistry and macroinvertebrate diversity. Both studies highlight the importance of monitoring alpine surface waters for better understanding of abiotic and biotic responses to landscape transformation resulting from ongoing and rapid environmental change, especially in relation to glacial recession.