Author(s): Valeria Lencioni; Alessandra Franceschini; Elisa Stella; Alberto Bellin

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Keywords: Glacier-fed streams; Climate change; Sentinel species; Diamesa; Water temperature

Abstract: Maximum water temperature is one of the main ecological predictors driving invertebrate distribution in glacier-fed streams in the Alps. Three cold-stenothermal species have been selected as “threshold indicator taxa” of changes in community structure at Tmax > 6 °C. Glacier retreating will alter hydrological regimes, sediment transport, biogeochemical and contaminant fluxes from rivers to oceans. This will influence the natural environment, including biodiversity and the ecosystem services that glacier-fed rivers provide to humans. Among these the provision of water for agriculture and livestock, hydropower, and potable use. Understanding how climate change and, specifically, glacier retreat affect aquatic biodiversity in glacier-fed streams represents a future research challenge. A long term study was carried out to highlight the main ecological predictors driving invertebrate distribution in eight glacier-fed streams in the Southern Alps. Thirty-five sites belonging to four stream types were sampled for two decades. High glacial influence was associated mainly with low maximum water temperature (Tmax), high Glacial Index (calculated as a function of glacier area and distance from the glacier), and the abundance of four Diamesa (Diptera Chironomidae) species (D. steinboecki, D. goetghebueri, D. zernyi, and D. latitarsis). Change-point analysis and Threshold Indicator Taxa Analysis identified these Diamesa species as the taxa with the strongest preference for high percent glacier cover in the catchment (change point ~ 30%) and low Tmax (change point ~ 6 °C). These obligate glacial river invertebrates disappear at glacier cover < 30% and Tmax > 6 °C and can be considered as sentinel species of climate change. Co-occurrence of stochastic and deterministic assembly processes seem to drive spatio-temporal changes in glacial invertebrate communities. Temporal changes in the community structure were highlighted in sites fed by glaciers under different retreat rates.

DOI: https://doi.org/10.3850/978-981-11-2731-1_150-cd

Year: 2018