期刊
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
卷 109, 期 42, 页码 16963-16968出版社
NATL ACAD SCIENCES
DOI: 10.1073/pnas.1207305109
关键词
aquatic respiration; priming effect; source and age of labile OC; aquatic CO2 emissions; aquatic carbon cycle
资金
- National Science Foundation [DEB 0820725]
- National Science and Engineering Research Council of Canada
- Fonds quebecois de la recherche sur la nature et les technologies
- Hydro-Quebec
- Division Of Environmental Biology
- Direct For Biological Sciences [0820725] Funding Source: National Science Foundation
Northern rivers and lakes process large quantities of organic and inorganic carbon from the surrounding terrestrial ecosystems. These external carbon inputs fuel widespread CO2 supersaturation in continental waters, and the resulting CO2 emissions from lakes and rivers are now recognized as a globally significant loss of terrestrial production to the atmosphere. Whereas the magnitude of emissions has received much attention, the pathways of C delivery and processing that generate these emissions are still not well-understood. CO2 outgassing in aquatic systems has been unequivocally linked to microbial degradation and respiration of terrestrial organic carbon (OC), but the nature (i.e., age and source) of this OC respired in surface waters is largely unknown. We present direct radiocarbon measurements of OC respired by bacteria in freshwater aquatic systems, specifically temperate lakes and streams in Quebec. Terrestrial OC fuels much of the respiration in these systems, and our results show that a significant fraction of the respired terrestrial OC is old (in the range of 1,000-3,000 y B.P.). Because the bulk OC pools in these lakes is relatively young, our results also suggest selective removal of an old but highly bioreactive terrestrial OC pool and its conversion to CO2 by bacteria. The respiration of ancient C-14-depleted terrestrial C in northern lakes and rivers provides a biological link between contemporary aquatic carbon biogeochemistry and paleo-conditions in the watershed, and it implies the aquatic-mediated return to the atmosphere of C putatively considered permanently stored, thus challenging current models of long-term C storage in terrestrial reservoirs.
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