Abstract
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.
Highlights
Multiple stressors drive environmental change on a global scale, including the effects of the loss of biodiversity on ecosystem functioning (Vorosmarty et al, 2010; Rockstrom et al, 2009; Baert et al, 2016)
As freshwater invertebrates have a long history as model test organisms, the relatively large amount of data available in the published literature allows us to interrogate of the role that the interaction of environmental and chemical stressors plays in altering the life history traits
Limited information can be extracted from the relationship between the temperature and growth and reproduction (Fig. 1A, B) because the data points are all in the 70% to 100% range
Summary
Multiple stressors drive environmental change on a global scale, including the effects of the loss of biodiversity on ecosystem functioning (Vorosmarty et al, 2010; Rockstrom et al, 2009; Baert et al, 2016). Organisms may alter their life history traits in response to these natural environmental stressors (e.g. low dissolved oxygen concentrations, food limitations, non-optimal temperatures, predation threats, or parasitism) (Boersma and Vijverberg, 1995; Hall, 1964; Homer and Waller, 1983; Seidl et al, 2005a; Connolly et al, 2004; Filho et al, 2011), including potentiation of effects or physiological mitigation (Hanazato, 1996; Penttinen and Holopainen, 1995; Seidl et al, 2005b; Coors and De Meester, 2008). Understanding the joint action of stressors can be a help in unravelling the combined adverse effects of multiple stressors that affect many ecosystems, and further, can be a contributing factor in understanding the qualities that new chemicals should have to exhibit high functional performance but limited effects on non-target environmental species (Schäfer and Piggott, 2018)
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