Estimating isotopic turnover rates using DEB theory

Abstract

The isotopic turnover rate (λ) quantifies the rate at which an organism’s tissues are renewed. It is a key parameter in dietary studies as it governs predator-prey dynamics and by extension the broader food web. However, λ has historically been difficult to estimate, typically requiring a combination of experiments, empirical data and modelling approaches. Mechanistic models offer a promising alternative for estimating λ. Among these, the Dynamic Energy Budget (DEB) theory provides a particularly relevant framework for describing organism metabolism. In this study, we propose a formal expression of λ within the DEB framework, expressed as a function of length or body mass, temperature, and food intake. Model predictions show good agreement with λ values reported in the literature. By linking λ estimation to DEB theory, this approach provides a user-friendly formulation and enables the estimation of condition-dependent isotopic turnover rates across more than 7000 species across a wide range of taxa.