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Does terrestrial organic carbon subsidize the planktonic food web in a clear‐water lake?
Author(s) -
Pace Michael L.,
Carpenter Stephen R.,
Cole Jonathan J.,
Coloso James J.,
Kitchell James F.,
Hodgson James R.,
Middelburg Jack J.,
Preston Nicholas D.,
Solomon Christopher T.,
Weidel Brian C.
Publication year - 2007
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.2007.52.5.2177
Subject(s) - dissolved organic carbon , phytoplankton , food web , zooplankton , copepod , pelagic zone , total organic carbon , plankton , environmental chemistry , environmental science , organic matter , microbial food web , carbon cycle , carbon fibers , ecology , chemistry , biology , nutrient , trophic level , ecosystem , crustacean , materials science , composite number , composite material
Allochthonous organic carbon can subsidize consumers in aquatic systems, but this subsidy may only be significant in relatively small systems with high organic matter loading. We tested the importance of allochthonous carbon to consumers in a relatively large (258,000 m 2 ) clear‐water lake by adding H 13 CO 3 daily for 56 d. Dissolved inorganic carbon (DIC) was substantially enriched in 13 C by the addition, but it was also variable over diel cycles because of exchange with the atmosphere and photosynthesis. By measuring the δ 13 C value of a physically separated phytoplankton concentrate as well as the δ 13 C of phospholipid fatty acids, we were able to follow 13 C‐labeling dynamics of specific groups of phytoplankton and bacteria. The δ 13 C values of particulate organic carbon (POC), dissolved organic carbon (DOC), phytoplankton, bacteria, zooplankton, and the invertebrate predator, Chaoborus spp. all increased to a maximum during the addition and declined once the addition ceased. Autochthony (% C derived from internal primary production) of carbon pools (POC, DOC) and consumers was assessed by fitting dynamic models to time series of δ 13 C. Autochthonous carbon was the dominant source (88‐100%) for POC, gram‐positive bacteria, a copepod, zooplankton biomass, and Chaoborus spp. Autochthonous carbon provided a lower fraction (<70%) of carbon to DOC, gram‐negative bacteria, and cladoceran zooplankton. In comparison to smaller and more humic lakes, terrestrially derived allochthonous C was less significant to the pelagic food web in this larger, clear‐water lake. Among lakes, the relative importance of autochthonous versus allochthonous carbon to planktonic consumers is positively correlated to the ratio of color (absorbance of light at 440 nm, an indicator of terrestrially derived organic carbon) to chlorophyll.