The role of glaciers as sources of stream nutrients in a high mountain catchment

In the high mountain environments, streams often appear nutrient-limited. In glaciated catchments however, glacier meltwater acts as sources of nitrogen (N) and phosphorus (P) to downstream ecosystems, but research investigating the spatio-temporal control that mountain glaciers are exerting on stream nutrient dynamics are rare, particularly in the Alps. In this study, we rely on a synoptic spatially distributed sampling of the main glacier-fed stream and major tributaries in a Swiss catchment. By applying a mixing model to estimate glacier meltwater fractions at different locations of the fluvial network, we correlate glacier meltwater contribution with stream nutrient concentrations to depict the glacier control. Moreover, we show that glaciers not only release high quantities of nitrate but also modify the relative abundance of N-species. Finally, we assess phosphate, ammonium and nitrate loads from glacier-fed and groundwater-fed streams to highlight the importance and diversity of glaciers as sources of streamwater nutrients at catchment scale.