Collaborative Research: Testing for nutrient limitation in alpine snow algae ecosystems

Climate change is driving massive changes in the amount of frozen water present on Earth (the cryosphere). An increasingly well-recognized factor that interacts with climate change to amplify the melting of ice and snow is the proliferation of algae that bloom on the snow surface (snow algae). Current understanding of the factors that control the abundance of snow algae, and thus their impact on snow and ice melt, is incomplete, especially in alpine environments where glaciers and snowfields are critical components of the water supply and are particularly susceptible to climate change. This project will examine an important but understudied driver of snow algae abundance – the variable input of key nutrient elements (nitrogen and phosphorus) via atmospheric deposition (in snow, rain, and dust). This project leverages and develops the capacities of an interdisciplinary team involving faculty, a postdoctorate, a graduate student, and undergraduates in a project of broad societal relevance given the crucial role of mountain snow in water supplies globally. Collectively, these studies will be among the first to explicitly test for nutrient limitation of alpine snow algae, significantly enhancing current understanding of how nutrient supplies drive large-scale ecosystem dynamics in the cryosphere. In particular, this information is critical for understanding and forecasting the role of snow algae in driving cryosphere loss, a process that ultimately has major impacts on sea level rise and freshwater supply. Project personnel will develop and deliver a unique 'Cryosphere Ecology' undergraduate field class that will integrate key topics and concepts in ecosystem ecology, microbiology, and snow science. Public outreach will include contacts with water resource stakeholders and managers as well as communication to broader audiences via existing public outreach channels.

This research will examine the impacts of nitrogen and phosphorus inputs on snow algae in six study regions in the western USA across a gradient of atmospheric nutrient deposition. The project has three focal questions: 1) How are snow algae biomass, productivity, and carbon:nitrogen:phosphorus ratios related to patterns of nutrient (nitrogen, phosphorus) deposition and availability in mountains of the western USA? 2) How do these snow algae ecosystems respond to experimental nutrient enrichment? 3) How does proliferation of nutrient-driven snow algae affect albedo properties of snow and thus accelerate snow melt? To answer these questions, this project will assess how snow algae proliferate in snow formed from meltwater from the six study regions (using the unique capacity of the Subzero Research Laboratory at Montana State University) and test how nitrogen and phosphorus enrichment affect snow algae growth and its impact on albedo and melting under both field and laboratory conditions. Answering these questions will produce novel fundamental knowledge of the role of nutrient limitation in snow algae ecosystems and the connection between nutrient inputs and biological albedo reduction, facilitating better forecasting of snowmelt-driven water supplies in mountain regions and providing a basis for mitigating processes that drive inputs and transport of atmospheric pollutants. The project will also support development of an interdisciplinary course in cryosphere ecology, encompassing snow science, biogeochemistry, microbiology, and phycology.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.