THE EFFECTS OF MELTWATER SOURCE ON ALPINE AQUATIC ECOSYSTEMS IN THE INTERMOUNTAIN WEST

Climate change is leading to the loss of snow and ice in mountain regions. In North America, the mountain cryosphere has been in decline for the past 35 years. Glaciers have experienced significant mass loss, coinciding with increasingly variable precipitation patterns, which have led to an overall decrease in average seasonal snowpack across the Western United States. Internal ice features, such as rock glaciers—structures composed of a rock-ice matrix insulated by rock debris—are expected to persist in mountain environments, even as surface glaciers recede. However, these features remain understudied. These cryosphere features are key sources of water for mountain headwaters, which support sensitive alpine species and provide over 75% of the drinking water in the Western United States.

Meltwater sources are among the most critical factors influencing the physical and chemical processes in headwater streams. Although they cover a relatively small percentage of their catchment area, both surface and rock glaciers play a vital role in key ecological processes by maintaining streamflow throughout the melt season, regulating temperatures, supplying essential nutrients (nitrogen, phosphorus, and carbon), and releasing trace elements into aquatic ecosystems. Furthermore, meltwater from glaciers can negatively impact aquatic life by releasing harmful trace elements that can naturally occur in bedrock or be produced through mining, manufacturing, agriculture, and urbanization.

Our research aims to highlight the role meltwater sources, including seasonal snow, surface glaciers, and rock glaciers play in structuring the physical and biogeochemical processes in mountain streams. In the summer of 2024, we began a survey of mountain streams along a latitudinal gradient from Glacier National Park (MT) to the Teton Range (WY) and the Wasatch (UT). We sampled 18 streams fed by varying meltwater sources and visited each three times during the summer (early, mid, and late season) to capture intra-seasonal variations. During each visit, we collected water samples for analysis of key nutrients (nitrogen, phosphorus, and carbon), major ions, and trace elements, and documented physical site conditions. This data can inform future conservation efforts for sensitive aquatic species and management strategies (i.e., downstream water quality treatment and flow management) to mitigate negative ecological impacts from changing meltwater sources.