Journal of Geophysical Research: Biogeosciences

Cover image for Vol. 121 Issue 3

Impact Factor: 3.426

ISI Journal Citation Reports © Ranking: 2014: 19/175 (Geosciences Multidisciplinary)

Online ISSN: 2169-8961

Associated Title(s): Journal of Geophysical Research

Altitude controls carbon dioxide in boreal lakes

Organic matter present in lakes, derived either from land-based sources (e.g., plants, soil, sediments) or from in situ processes (e.g., degrading detritus in the water), could be an important player in the global carbon cycle or even a significant source of the atmospheric carbon dioxide (CO2) budget. The partial pressure of CO2 in surface waters (pCO2) drives the escape of CO2 to the atmosphere. Hence, scientists have long suspected that the relationship between pCO2 and the dissolved organic matter (DOC) in lake waters reflects the relative contribution of the environment and in situ processes to the high-latitude carbon budget. Combining measurements of DOC and pCO2 from nearly 200 lakes across Quebec, Canada with an additional 13 lake-based studies from temperate regions across the northern hemisphere, Lapierre and del Giorgio (2012) suggest that on a regional scale the elevation of lakes is one of the strongest controls on the relationship between DOC and pCO2 in boreal lakes. High-altitude lakes typically have small watersheds and faster drainage; the water in these lakes has shorter residence time and as such land-derived sources of CO2, contribute to pCO2 in high-altitude lakes. On the other hand, low-altitude lakes are typically large and drain a larger watershed, and the residence time of water is typically longer. As a result, in low-altitude lakes photochemical reactions causing degradation of organic material control the DOC, which accounts for the pCO2 in the surface waters in these lakes. Thus, the DOC in low-altitude lakes acts as source of CO2 released to the atmosphere. The study reveals that, in fact, the balance between in situ processes and external input, which in turn determines the source of CO2 from boreal lakes, is mainly driven by altitude.

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