Mean Species Abundance as a Measure of Ecotoxicological Risk

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 (HC 5 s) based on MSA relationships are systematically higher than SSD-based HC 5 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.

Toward Assessing Absolute Environmental Sustainability of Chemical Pollution

“…Therefore, in addition to toxicity-based considerations of species sensitivity to compounds, species richness and ecosystem functions should be considered. One approach developed by Hoeks et al . uses species-specific exposure-response models with population growth concepts to assess the effects of chemical exposures on mean species abundance.…”

“…Therefore, in addition to toxicity-based considerations of species sensitivity to compounds, species richness and ecosystem functions should be considered. One approach developed by Hoeks et al 34 uses species-specific exposure-response models with population growth concepts to assess the effects of chemical exposures on mean species abundance. While this approach is more constrained by data availability than traditional SSD-based approaches, it shows promise for incorporating species richness into chemical effect endpoints.…”

Harnessing Computational Methods to Characterize Chemical Impacts on Biodiversity

“…While the focus of most computational approaches assessing species’ sensitivity to chemical exposures characterize sensitivity across species rather than changes in abundance, one preliminary approach to estimate how chemical exposures may alter species abundance is the mean species abundance relationship (MSAR) . Preliminary estimates of species abundance can also be developed using probabilistic approaches to model different ratios of species abundance to assess potential biodiversity impacts.…”

“…While the focus of most computational approaches assessing species' sensitivity to chemical exposures characterize sensitivity across species rather than changes in abundance, one preliminary approach to estimate how chemical exposures may alter species abundance is the mean species abundance relationship (MSAR). 56 Preliminary estimates of species abundance can also be developed using probabilistic approaches to model different ratios of species abundance to assess potential biodiversity impacts. Other approaches can harness existing data sets on species occurrence (e.g., data in GBIF) to build ML and/or statistical methods to predict species occurrence (or distributions of occurrence) in different ecosystems (i.e., cross-region extrapolation).…”

Contaminant curiosity and pollutant puzzles: Conceptual insights in ecotoxicity and practical implementation of higher-tiered risk assessment.

“…Just as intraspecific concentration-response relationship parameters (EC 50 , β) can be related to population dynamics of a species, one may mechanistically and statistically link interspecies sensitivity distributions quantities (HC 50 , β) to community development. Initial attempts demonstrated that the potentially affected fraction (PAF) of species as described above can be related to the mean species abundance (MSA an often-used indicator in global change studies (Hoeks et al, 2020). Even more, impact of pesticides on MSA as calculated from PAF was confirmed by a decrease of macrofauna abundance in the field (Thunnissen et al, 2020; 2022).…”