Glacier runoff impacts the stoichiometry of riverine nutrient export from coastal Alaskan catchments

Understanding the impacts of glacier change on riverine ecosystems is limited by a lack of multi-year studies in glacierized mountain catchments quantifying the magnitude and stoichiometry of riverine biogeochemical yields. Here we evaluate riverine concentration-discharge relationships using the power function between daily runoff and element yields and stoichiometry across 10 catchments of varying glacial coverage within two climatically distinct regions in the Gulf of Alaska. Our multi-year study showed that biogeochemical stoichiometry and concentration-discharge relationships for dissolved carbon, nitrogen, and phosphorus varied significantly with catchment glacier coverage across both regions. This stoichiometric variability could drive regional differences in proglacial riverine food webs given that high trophic levels in low productivity rivers are generally driven by bottom-up controls. The coherence of our findings across the Gulf of Alaska suggests that observed patterns in concentration-discharge relationships are likely globally generalizable to catchments in which discharge is dominated by glacier ice and/or snowmelt. Concentration-discharge relationships for dissolved carbon, nitrogen, and phosphorus in Gulf of Alaska rivers are driven by glacier catchment coverage, according to analysis of water samples from the Gulf of Alaska.