Understanding food web structure in high-elevation streams of the Teton Range

Abstract

Climate change is dramatically altering high-elevation streams around the world through the recession of glaciers and other meltwater sources. Rapidly changing hydrological regimes imperil entire communities of mountain stream biodiversity. We have monitored high-elevation streams in the Teton Range since 2015, with a specific focus on understanding how hydrological source variation affects the susceptibility of downstream communities, and the stoneflies Zapada glacier and Lednia tetonica, to climate-induced impacts. We monitor streams fed by three sources – glaciers, snowfields, and subterranean ice (primarily rock glaciers). Streams fed by subterranean ice – “icy seeps” – are predicted to persist on the landscape longer than their surface counterparts due to the inherent thermal buffering of their source ice provided by debris cover. We hypothesize that icy seep communities will be buffered against climate-induced environmental changes and will act as key refugia for cold-adapted communities. In late 2019, the conservation implications of our work were escalated by the listing of one of the key species we study, the stonefly Zapada glacier, under the US Endangered Species Act due to climate-induced habitat loss. In 2020, our first objective was to collect a 6th year of continuous data for core sites and continue investigating longer term signals in the data. For our second objective, we addressed another large gap in contemporary knowledge of high-elevation stream ecology: food web structure. Despite imminent threats to biodiversity in headwater streams, little is known of the basic quantity and quality of basal resources in mountain streams, how these resources vary with stream type, and linkages between feeding groups. Additionally, little is known about the diet or trophic position of Zapada glacier. We will use an array of modern approaches, including stable isotopes and nutrient content analyses, to generate a high-resolution view of food web structure in the high Teton Range. Our results will inform management in the Teton Range while also shedding new light on a standing challenge in mountain stream ecology worldwide. Featured photo by Bonnie Robinson, taken from the UW-NPS photo collection.