Matrix models can be used to extrapolate effects of environmental toxicants on life history parameters to the population level. In applications of these models, life history parameters are usually treated as independent factors; however, they are actually strongly linked to each other. To interpret the effect of toxicants on life history parameters considering their interrelatedness the dynamic energy budget (DEB) theory can be applied. This theory is based on closed energy and mass balances and describes in a mechanistic way the acquisition and use of energy by individuals. In the present study we extended an existing combined DEB and matrix population model with an approach to take covariability of the DEB parameters into account. This was accomplished by estimating the joint posterior distribution of the parameters using Bayesian statistics. We used this model to extrapolate effects of copper in the common earthworm Dendrobaena octaedra to the population level.