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Long-lasting effects of experimental flow intermittency on alpine stream macroinvertebrates (Val Roseg, Switzerland)

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posted on 09.05.2022, 23:40 by AM Drost, Andre SiebersAndre Siebers, A Paillex, B Misteli, ETHM Peeters, CT Robinson
Changing weather patterns and receding glaciers are predicted to increase flow intermittency in alpine streams. If aquatic macroinvertebrate communities largely comprise taxa adapted to perennial flows, an increase in flow intermittency substantially reduces biodiversity and affects functional processes. We conducted a before-after-control-impact field experiment to examine how macroinvertebrate communities in an alpine headwater stream responded to and recovered from a repeated experimental increase in flow intermittency. Flow in one channel was manipulated to simulate increased summer intermittency (June–September) over two consecutive years, whilst an adjacent channel served as a control. We monitored the density of benthic macroinvertebrates, periphyton and organic matter at approximately monthly intervals over three years during the snow-free period. Before manipulation, both channels had similar ecological properties. The flow manipulation reduced the overall macroinvertebrate density, and especially the proportional rheophile density, across both years. Recovery of the macroinvertebrate community following experimental flow intermittency took more than a year, and longer than our study period. This could be due to long aquatic life stages, dispersal limitation and biotic interactions. We conclude that climate-induced changes in alpine stream flow regimes can lead to a fundamental shift in macroinvertebrate assemblages through local extinctions, mostly of rheophilic species.


Open Access funding provided by Lib4RI -Library for the Research Institutes within the ETH Domain: Eawag, Empa, PSI & WSL. Funding for this project was provided through Eawag Discretionary Funds for Research, the Ernst Gohner foundation, Gelbert foundation, and Department of Nature and Environment, Canton Graubunden. We thank Marion Caduff, Larissa Schadler, Jorrit Mesman, Salome Baumann, Gabriele Consoli and Christa Jolidon for assistance in the field and laboratory. We thank Christian Ebi for development of the electrical resistance loggers. We thank the AuA Lab at Eawag for analysis of water chemistry. We thank Gemeinde Pontresina for road access to Val Roseg. We are grateful to Lucrezia and Wolfgang Pollak-Thom, and staff of the Hotel Restaurant Roseg Gletscher, for their hospitality during our many visits.


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