Interpreting stable isotopes in food webs: Recognizing the role of time averaging at different trophic levels

C. M. O'Reilly, R. E. Hecky, Andrew Cohen, P. D. Plisnier

Research output: Contribution to journalArticle

176 Citations (Scopus)

Abstract

Lake Tanganyika, East Africa, has a simple pelagic food chain, and trophic relationships have been established previously from gut-content analysis. Instead of expected isotopic enrichment from phytoplankton to upper level consumers, there was a depletion of 15N in August 1999. The isotope signatures of the lower trophic levels were an indicator of a recent upwelling event, identified by wind speed and nitrate concentration data, that occurred over a 4-d period several days prior to sampling. The isotope structure of the food web suggests that upwelled nitrate is a nutrient source rapidly consumed by phytoplankton, but the distinctive signature of this nitrate is diluted by time averaging in the upper trophic levels. This time averaging is a consequence of the fact that the isotopic signature of an organism is related to variable nitrogen sources used throughout the life of the organism. This study illustrates the importance of recognizing differences in time averaging among trophic levels.

Original languageEnglish (US)
Pages (from-to)306-309
Number of pages4
JournalLimnology and Oceanography
Volume47
Issue number1
StatePublished - 2002

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trophic level
stable isotopes
food webs
food web
stable isotope
nitrates
nitrate
isotopes
phytoplankton
isotope
Lake Tanganyika
organisms
Eastern Africa
food chain
wind speed
trophic relationships
upwelling
digestive system
wind velocity
nutrient

ASJC Scopus subject areas

  • Aquatic Science
  • Oceanography

Cite this

Interpreting stable isotopes in food webs : Recognizing the role of time averaging at different trophic levels. / O'Reilly, C. M.; Hecky, R. E.; Cohen, Andrew; Plisnier, P. D.

In: Limnology and Oceanography, Vol. 47, No. 1, 2002, p. 306-309.

Research output: Contribution to journalArticle

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