Validating static food web model diet matrices using stable isotope simulation

Monte Carlo simulation of stable isotope signatures in a Northern Gulf of Mexico EwE food web validates primary carbon sources and benthic–pelagic pathway contributions, while exposing diet-matrix mismatches.

• Why it matters: Stomach-content-derived diets may not reflect long-term assimilated consumption, and because trophic interactions set model structure, diet-matrix uncertainty can undermine ecosystem-model acceptance.
• What they did: A matrix-based mixing model was used to simulate consumer δ13C and δ34S from a published Northern Gulf of Mexico EwE model, propagating uncertainty via Monte Carlo sampling of basal source signatures and trophic discrimination factors.
• The result: Predicted and empirical isotope measurements agreed in isotope space but mismatched energy pathways; residual diagnostics and model scoring ranked alternative diet configurations, and redundancy analysis linked mismatch to within-group species coverage differences between stomach contents and isotope sampling.

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