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Whole-lake carbon-13 additions reveal terrestrial support of aquatic food webs

Whole-lake carbon-13 additions reveal terrestrial support of aquatic food webs Ecosystems are supported by organic carbon from two distinct sources. Endogenous carbon is produced by photosynthesis within an ecosystem by autotrophic organisms. Exogenous carbon is produced elsewhere and transported into ecosystems. Consumers may use exogenous carbon with consequent influences on population dynamics, predator–prey relationships and ecosystem processes 1 . For example, exogenous inputs provide resources that may enhance consumer abundance beyond levels supported by within-system primary production 2 . Exogenous fluxes of organic carbon to ecosystems are often large, but this material is recalcitrant and difficult to assimilate, in contrast to endogenously produced organic matter, which is used more easily 3,4 . Here we show, by the experimental manipulation of dissolved inorganic 13C in two lakes, that internal primary production is insufficient to support the food webs of these ecosystems. Additions of NaH13CO3 enriched the 13C content of dissolved inorganic carbon, particulate organic carbon, zooplankton and fish. Dynamics of 13C indicate that 40–55% of particulate organic carbon and 22–50% of zooplankton carbon are derived from terrestrial sources, showing that there is significant subsidy of these ecosystems by organic carbon produced outside their boundaries. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Nature Springer Journals

Whole-lake carbon-13 additions reveal terrestrial support of aquatic food webs

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References (52)

Publisher
Springer Journals
Copyright
Copyright © 2004 by Macmillan Magazines Ltd.
Subject
Science, Humanities and Social Sciences, multidisciplinary; Science, Humanities and Social Sciences, multidisciplinary; Science, multidisciplinary
ISSN
0028-0836
eISSN
1476-4687
DOI
10.1038/nature02227
Publisher site
See Article on Publisher Site

Abstract

Ecosystems are supported by organic carbon from two distinct sources. Endogenous carbon is produced by photosynthesis within an ecosystem by autotrophic organisms. Exogenous carbon is produced elsewhere and transported into ecosystems. Consumers may use exogenous carbon with consequent influences on population dynamics, predator–prey relationships and ecosystem processes 1 . For example, exogenous inputs provide resources that may enhance consumer abundance beyond levels supported by within-system primary production 2 . Exogenous fluxes of organic carbon to ecosystems are often large, but this material is recalcitrant and difficult to assimilate, in contrast to endogenously produced organic matter, which is used more easily 3,4 . Here we show, by the experimental manipulation of dissolved inorganic 13C in two lakes, that internal primary production is insufficient to support the food webs of these ecosystems. Additions of NaH13CO3 enriched the 13C content of dissolved inorganic carbon, particulate organic carbon, zooplankton and fish. Dynamics of 13C indicate that 40–55% of particulate organic carbon and 22–50% of zooplankton carbon are derived from terrestrial sources, showing that there is significant subsidy of these ecosystems by organic carbon produced outside their boundaries.

Journal

Nature – Springer Journals

Published: Jan 15, 2004

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