Collaborative Research: What Underpins the High Bioavailability of Glacier Organic Matter?

Glaciers are retreating at rapid rates, yet critical questions remain about their role in the Earth system. As glaciers melt, they release ancient, biologically available dissolved organic matter (DOM) into water. This organic material can support downstream food webs, and release carbon that was trapped in ice to the atmosphere. Recent research shows that glacier DOM is deposited from the atmosphere and also grown on the surface by algae and other microbial organisms. The relative importance of new versus ancient carbon sources driving the observed bioavailability of glacier DOM is largely unknown. This has important implications for understanding bio-feedbacks from glaciers in global carbon cycling. This project provides opportunities for undergraduate students and an early-career researcher with training in biogeochemistry, environmental biology, and Arctic science. The collaboration extends beyond the funded team to include scientists at the National High Magnetic Field Laboratory, enabling knowledge transfer and access to world-leading analytical facilities. Results will be disseminated to the public through science fairs and educational outreach at the U.S. Forest Service Mendenhall Glacier visitor center. The researchers have developed a respiratory carbon recovery system (RCRS) to directly analyze the age and source of glacier DOM consumed by microbes. Preliminary results support the hypothesis that modern microbial production on the glacier drives the high bioavailability of ancient DOM. Using analytical techniques, including ultrahigh-resolution mass spectrometry, radiocarbon dating, endmember source analysis, and RCRS incubation experiments, this research will investigate whether the source of respired glacier DOM varies between glacier ecosystems and through the melt season in the Alaskan Coastal Mountains. This will establish if there is homogeneity in the glacial carbon released to downstream food webs that support ocean fisheries. These results will improve understanding of the quantity, timing and sources of carbon delivery to aquatic ecosystems in glacier runoff. Ultimately, these results will provide critical insights into how glacier ecosystems function and how their loss may affect downstream freshwater and marine ecosystems, and global carbon cycling, with ramifications for resource-dependent communities and fisheries. 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.