Long-term Patterns of Stream Macroinvertebrates in an Alpine Cirque Landscape

Abstract

Abstract Alpine landscapes are notable regarding their sensitivity to environmental change. Surface waters are especially sensitive as many are influenced by glacial meltwaters that are diminishing with the retreat of glaciers worldwide. The Macun Lakes region is an alpine cirque landscape housing a number of lakes interconnected by streams. Surface waters, 10 stream sites in the present study, have been monitored in mid-summer since the year 2001 for physico-chemistry, periphyton and macroinvertebrates (including 74 species of chironomids). Water physico-chemistry revealed that the two main basins in the catchment differed, reflecting the inputs of rock glacier waters in the south basin. However, trends suggest that waters are becoming more similar as rock glacier inputs diminish over time along with a general decrease in nitrogen levels in all waters. Periphyton biomass showed some spatial differences among sites and with a general decrease following 2010. Macroinvertebrate assemblages, including chironomids, clearly differed among basins and longitudinally along the stream network in each basin. Notably, no significant temporal trend was observed in the long-term data for macroinvertebrates, as well as chironomids, at the monitored sites. The results suggest that lotic macroinvertebrates may be buffered by the interconnectedness of streams with lakes in the landscape that mitigate major response patterns of running waters to environmental change.