Stable isotopic evidence for high microbial nitrate throughput in a High Arctic glacial catchment

• Main Author: Ansari, A. H.
• Format: Text
• Language: English
• Published: 2018
• Subjects: Arctic
• Online Access: https://doi.org/10.5194/tc-2016-59; https://tc.copernicus.org/preprints/tc-2016-59/

During summer, streams in the Arctic redistribute and export the solute derived from snowpack (accumulated by atmospheric deposition) melting and sediment weathering in its flowpath. The redistribution of dissolved nitrogen undergoes biogeochemical processing (nitrate production and consumption in flowpath). To assess the quantitative impact of these processing, NO 3 − -N, NH 4 + -N, total dissolved nitrogen (TDN) and stable isotope composition of the snowpacks was compared with the subglacial and proglacial stream waters. Snowpack derived dissolved organic nitrogen (DON) and NH 4 + -N provided the most probable substrate for additional NO 3 − -N produced by microbial nitrification. The flux of microbially produced and assimilated NO 3 − -N in the eastern and western proglacial streams were 1.64 ± 1.41 kg Day −1 and 1.41 ± 1.43 kg Day −1 and, 1.39 ± 1.41 kg Day −1 and 1.35 ± 1.43 kg Day −1 respectively. These overwhelming amounts of NO 3 − -N production and assimilation reveals a hitherto unknown level of microbial processing in the Arctic glacial ecosystem. The balance between the two microbial processes and consistently low dissolved inorganic nitrogen (NH 4 + -N + NO 3 − -N) in the proglacial streams indicate a fast in-stream recycling of assimilated NO 3 − -N however, the fate of such NO 3 − -N remains unresolved.