Glaciers Provide a Source of Organic Matter to Stimulate Biogeochemical Processes

Abstract

Glaciers export dissolved organic matter (DOM) to downstream ecosystems in meltwater. A stream’s DOM pool is influenced by input from surrounding soils and vegetation whereas glacial meltwater has the addition of glacially-derived DOM to the bulk DOM pool. Current data availability studying DOM in glacial streams is largely limited to polar and midlatitude glaciers as studies of DOM content of equatorial glacierfed streams are extremely limited. Here, we use fluorescence spectroscopy to characterize how the optical properties of dissolved organic matter evolve along a glacial stream that flows from the Hermoso glacier on Volcan Cayambe, Ecuador. Results show that DOM characteristics change as the meltwater flows from higher elevation pure glacier meltwater to lower elevation streams that flow through different types of vegetation cover. Specifically, the DOM evolves from protein-like and microbiallike near the glacier terminus to more fulvic acid-like downstream near the vegetated area of the watershed. The transformation from protein-like to humic-like prior to the establishment of developed soils suggests that in-stream biogeochemical processes involving dissolved organic matter are occurring and that glaciers play a crucial role in providing DOM to aquatic ecosystems by stimulating the aquatic carbon cycle.