  Understanding the consequences of the combined effects of multiple
stressors-including stress from man-made chemicals is important for
conservation management, the ecological risk assessment of chemicals, and many
other ecological applications. Our current ability to predict and analyse the
joint effects of multiple stressors is insufficient to make the prospective
risk assessment of chemicals more ecologically relevant because we lack a full
understanding of how organisms respond to stress factors alone and in
combination. Here, we describe a Dynamic Energy Budget (DEB) based
bioenergetics model that predicts the potential effects of single or multiple
natural and chemical stressors on life history traits. We demonstrate the
plausibility of the model using a meta-analysis of 128 existing studies on
freshwater invertebrates. We then validate our model by comparing its
predictions for a combination of three stressors (i.e. chemical, temperature,
and food availability) with new, independent experimental data on life history
traits in the daphnid Ceriodaphnia dubia. We found that the model predictions
are in agreement with observed growth curves and reproductive traits. To the
best of our knowledge, this is the first time that the combined effects of
three stress factors on life history traits observed in laboratory studies have
been predicted successfully in invertebrates. We suggest that a re-analysis of
existing studies on multiple stressors within the modelling framework outlined
here will provide a robust null model for identifying stressor interactions,
and expect that a better understanding of the underlying mechanisms will arise
from these new analyses. Bioenergetics modelling could be applied more broadly
to support environmental management decision making.
