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Regulation of the nitrogen biogeochemistry of mountain lakes by subsidies of terrestrial dissolved organic matter and the implications for climate studies
Author(s) -
Bunting Lynda,
Leavitt Peter R.,
Weidman R. Paul,
Vinebrookeb Rolf D.
Publication year - 2010
Publication title -
limnology and oceanography
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.7
H-Index - 197
eISSN - 1939-5590
pISSN - 0024-3590
DOI - 10.4319/lo.2010.55.1.0333
Subject(s) - biogeochemistry , sediment , sedimentary rock , δ15n , sedimentary organic matter , dissolved organic carbon , environmental science , montane ecology , climate change , ecology , oceanography , hydrology (agriculture) , physical geography , δ13c , stable isotope ratio , geology , geochemistry , geography , biology , geomorphology , physics , geotechnical engineering , quantum mechanics
Stable isotopes of nitrogen (N) were analyzed in modern sediments of mountain lakes, dissolved organic matter (DOM), and sediment cores spanning the past 12,000 yr to test the hypothesis that spatial and temporal (100‐ 1000 yr) variation in the N content of mountain lakes is regulated by influx of allochthonous DOM. Analysis of spatial patterns in an elevation gradient of 75 mountain lakes revealed that most N was associated with DOM rather than inorganic N, particularly in subalpine lakes (, 1700 m above sea level). Similarly, analysis of N isotope ratios (δ 15 N) from 22 lakes showed that whole sediments of subalpine sites were significantly more depleted (0.74‰ ± 1.58‰) than were those of alpine lakes above 2200 m (3.04‰ ± 1.21‰), consistent with the depleted δ 15 N of isolated DOM (~1.3‰). Sedimentary δ 15 N values of Crowfoot Lake, presently near tree line, also varied greatly during the past 12,000 yr, with enriched values (~4%) during the alpine phases of the lake's history and depleted values (~1%) during the intervening subalpine phase (ca. 10,050‐4160 14 C yr before present) when DOM was abundant. In contrast, sedimentary δ 15 N values remained constant (~2.5%) at Snowflake Lake, an alpine reference site that never experienced a DOM‐rich subalpine phase. These analyses suggest that climate regulates N influx and lake biogeochemistry by changing the subsidies of terrestrial DOM, and warn that future climate change may initially reduce N influx on a decadal scale by reducing hydrologic transfer before increasing N subsidies on a centennial scale by increasing terrestrial production of DOM.