A new method to reconstruct quantitative food webs and nutrient flows from isotope tracer addition experiments

Andrés Lopez-Sepulcre, Matthieu Bruneaux, Sarah M. Collins, Rana El-Sabaawi, Alexander S. Flecker, Steven A. Thomas

Research output: Contribution to journalArticlepeer-review

2 Scopus citations


Understanding how nutrients flow through food webs is central in ecosystemecology. Tracer addition experiments are powerful tools to reconstruct nutrient flows by adding an isotopically enriched element into an ecosystem and tracking its fate through time. Historically, the design and analysis of tracer studies have varied widely, ranging from descriptive studies to modeling approaches of varying complexity. Increasingly, isotope tracer data are being used to compare ecosystems and analyze experimentalmanipulations. Currently, a formal statistical framework for analyzing such experiments is lacking, making it impossible to calculate the estimation errors associated with the model fit, the interdependence of compartments, and the uncertainty in the diet of consumers. In this article we develop a method based on Bayesian hidden Markov models and apply it to the analysis of 15N‐NH4 1 tracer additions in two Trinidadian streams in which light was experimentally manipulated. Through this case study, we illustrate how to estimateN fluxes between ecosystem compartments, turnover rates of N within those compartments, and the associated uncertainty. We also show how the method can be used to compare alternative models of food web structure, calculate the error around derived parameters, and make statistical comparisons between sites or treatments.

Original languageEnglish (US)
Pages (from-to)964-982
Number of pages19
JournalAmerican Naturalist
Issue number6
StatePublished - Jun 1 2020


  • Food webs
  • Funding was provided by grants from the Academy of Finland (295941) to A.L.-S. and a Frontiers in Integrative Biological Research (FIBR) grant from the National Science Foundation (EF0623632) to A.S.F. and S.A.T
  • Hidden Markov model (HMM)
  • Isotope tracer addition
  • Model selection
  • Nutrient uptake
  • State-space models

ASJC Scopus subject areas

  • Ecology, Evolution, Behavior and Systematics


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