Abstract
Chemical pollution of surface waters is considered an important driver for recent declines in biodiversity. Species sensitivity distributions (SSDs) are commonly used to evaluate the ecological risks of chemical exposure, accounting for variation in interspecies sensitivity. However, SSDs do not reflect the effects of chemical exposure on species abundance, considered an important endpoint in biological conservation. Although complex population modeling approaches lack practical applicability when it comes to the routine practice of lower tier chemical risk assessment, in the present study we show how information from widely available laboratory toxicity tests can be used to derive the change in mean species abundance (MSA) as a function of chemical exposure. These exposure–response MSA relationships combine insights into intraspecies exposure–response relationships and population growth theory. We showcase the practical applicability of our method for cadmium, copper, and zinc, and include a quantification of the associated statistical uncertainty. For all 3 metals, we found that concentrations hazardous for 5% of the species (HC5s) based on MSA relationships are systematically higher than SSD‐based HC5 values. Our proposed framework can be useful to derive abundance‐based ecological protective criteria for chemical exposure, and creates the opportunity to assess abundance impacts of chemical exposure in the context of various other anthropogenic stressors. Environ Toxicol Chem 2020;39:2304–2313. © 2020 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.
Highlights
Chemical pollution of surface waters is considered an important driver of the deterioration of freshwater ecosystems (Ginebreda et al 2014; Malaj et al 2014; Bernhardt et al 2017)
This difference was smaller for Cu and Zn, still 70% of the species had survival‐based exposure–abundance curves outside the 95% confidence interval (CI) around the curves based on both survival and reproduction
The difference between the default MSA relationship (MSAR) curve including the effects on both reproduction and survival and the alternative MSAR curve solely based on reproduction varied among the 3 metals studied (Figure 4)
Summary
Chemical pollution of surface waters is considered an important driver of the deterioration of freshwater ecosystems (Ginebreda et al 2014; Malaj et al 2014; Bernhardt et al 2017) In this context, species sensitivity distributions (SSDs) are commonly applied to assess the aquatic risks of chemicals (Posthuma et al 2001; de Zwart and Posthuma 2005). The most realistic approaches to assess the impacts of chemical exposure on a community level are mesocosm experiments in which ecosystem structure or function are monitored over time (Iwasaki et al 2018) with diagnostic assessments of chemical pollution in surface waters as complex but complete approaches. Modeling approaches have been proposed instead to integrate biological interactions and indirect ecological effects in chemical risk assessment practice
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