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Abstract
Glacial runoff is predicted to increase in many parts of the Arctic with climate change, yet little is known about the biogeochemical impacts of meltwaters on downstream freshwater ecosystems. Here we document the contemporary limnology of the rapidly changing glacierized watershed of the world’s largest High Arctic lake (Lake Hazen), where warming since 2007 has increased delivery of glacial meltwaters to the lake by up to 10-times. Annually, glacial meltwaters accounted for 62–98% of dissolved nutrient inputs to the lake, depending on the chemical species and year. Lake Hazen was a strong sink for NO3−-NO2−, NH4+ and DOC, but a source of DIC to its outflow the Ruggles River. Most nutrients entering Lake Hazen were, however, particle-bound and directly transported well below the photic zone via dense turbidity currents, thus reinforcing ultraoligotrophy in the lake rather than overcoming it. For the first time, we apply the land-to-ocean aquatic continuum framework in a large glacierized Arctic watershed, and provide a detailed and holistic description of the physical, chemical and biological limnology of the rapidly changing Lake Hazen watershed. Our findings highlight the sensitivity of freshwater ecosystems to the changing cryosphere, with implications for future water quality and productivity at high latitudes.
Highlights
Global glacier volume is expected to decline by 29–41% by 21001, with coincident changes to downstream runoff[2,3]
The land to ocean aquatic continuum (LOAC) framework has hitherto only been applied in temperate forested and agricultural watersheds and has focused primarily on rivers and streams, even though
Our objectives were to: (a) describe the physical, chemical and biological limnology of the Lake Hazen watershed within the context of a glacierized LOAC; (b) quantify the impact of in-lake processing of glacial meltwaters using hydrological input-output budgets; (c) describe water column plankton community assemblages and sediment biogeochemical processes in relation to glacial inputs; and, (d) apply ecosystem stoichiometry to identify locations of nutrient mobilization and retention across the glacierized LOAC
Summary
Global glacier (non-ice sheet) volume is expected to decline by 29–41% by 21001, with coincident changes to downstream runoff[2,3]. Lakes are becoming increasingly dynamic components of the LOAC as their area and numbers increase globally in response to rapid glacial melt[22,23] These proglacial lakes are typically located in sparsely vegetated catchments with poorly developed soils, which limits allochthonous carbon inputs but facilitates the entrainment of mobilized mineral sediments and nutrients. Our objectives were to: (a) describe the physical, chemical and biological limnology of the Lake Hazen watershed within the context of a glacierized LOAC; (b) quantify the impact of in-lake processing of glacial meltwaters using hydrological input-output budgets; (c) describe water column plankton community assemblages and sediment biogeochemical processes in relation to glacial inputs; and, (d) apply ecosystem stoichiometry to identify locations of nutrient mobilization and retention across the glacierized LOAC.
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