Seasonal and functional variation in the trophic base of intermittent Alpine streams

In high-altitude Alpine streams, seasonal cycles of snowmelt, glacial melt, and rainfall drive variation in the availability of algal food resources. Yet high-altitude streams also exhibit varying degrees of flow intermittency, from solely winter-drying streams to others that dry periodically throughout summer and autumn. These environmental drivers may interact in different ways to determine the functional trophic base of macroinvertebrates inhabiting high-altitude streams. Here, we estimated the proportional contribution of autochthonous resources to the assimilated diets of benthic macroinvertebrates in 26 headwater streams of Val Roseg, a high Alpine glacial catchment, using stable isotope analysis (δ13C and δ15N) of different macroinvertebrate families and their potential food sources. We compared dietary estimates along a gradient of flow intermittency and across 3 seasons (Alpine spring, summer and autumn). Assimilation from autochthonous sources was highest for collector-gathere...

在高海拔阿尔卑斯溪流中，融雪、冰川融水与降雨的季节循环驱动着藻类食物资源可获得性的动态变化。同时，高海拔溪流存在不同程度的水流间歇性，涵盖仅冬季干涸的溪流，以及在夏季、秋季周期性断流的溪流。这些环境驱动因子可通过不同的相互作用方式，决定栖息于高海拔溪流的大型底栖无脊椎动物的功能营养基础。本研究以高阿尔卑斯冰川流域瓦洛泽格（Val Roseg）的26条源头溪流为研究对象，通过对不同大型底栖无脊椎动物类群及其潜在食物源开展稳定同位素分析（δ¹³C与δ¹⁵N），估算了内源食物资源（autochthonous resources）在底栖大型无脊椎动物同化膳食中的占比。我们沿水流间歇性梯度，并结合阿尔卑斯春季、夏季与秋季三个季节，对膳食组成的估算结果开展了对比分析。结果显示，对于集食类群而言，从内源资源获取的同化量最高……