Single‐species acute lethal toxicity tests are not predictive of relative population and community effects of two salinity types

Abstract

The predominant approach to setting environmental quality guidelines for chemical contaminants to protect aquatic biodiversity involves the use of single-species toxicity tests, which often measure short-term mortality on a limited number of species. It is recognized that the results of these tests may not adequately protect biodiversity in ecosystems; however, it is implicitly assumed that these tests do indicate the relative effects of toxicants in ecosystems. Here, we test this implicit assumption by conducting an experiment in model freshwater ecosystems (mesocosms). We found this relative toxicity assumption was not supported for effects on stream macroinvertebrates comparing two salinity types, sodium bicarbonate (NaHCO 3 ) and salinity with the ionic composition of seawater, which are common contaminants from coal bed effluents and agriculture, respectively. Consequently, extrapolation from single-species toxicity estimates (representing effects on test populations) to the relative effects on natural populations and communities in nature is problematic, at least for NaHCO 3 and salinity with the ionic composition of seawater. Studies should test the implicit assumption of relative effects between other combinations of chemical stressors.

Documenting the impacts of increasing salinity in freshwater and coastal ecosystems: Introduction to the special issue

“…We know that species occur within communities and ecosystems, and that the interaction between them can modulate the sensitivity of individual species to stressors (Baillard et al 2020; Thompson et al 2021). Kefford et al (2021) and Arnott et al (2022) call for more community‐based toxicity tests and coordinated mesocosm studies that account for species interactions rather than single species toxicity tests performed in laboratories when salinity standards for the protection of aquatic ecosystems are developed. Results reported in this SI provide new knowledge about how lake and coastal ecosystems, zooplankton, plankton and microbial (algal, bacterial, and fungal) communities will likely respond to increasing salinity, not only with reductions in zooplankton abundance, but also with fewer species of zooplankton, and a consistent trophic shift towards primary producers and microbiota.…”

Toxicokinetics and bioaccumulation of silver sulfide nanoparticles in benthic invertebrates in an indoor stream mesocosm

“…For regulatory purposes, chemical substances' toxicity and bioaccumulation potential are usually assessed by conducting single-species laboratory tests. However, in order to protect biodiversity, it is required to perform more complex and realistic exposure scenarios (Kefford et al, 2021). Considering this, one of the aims of the present study was to assess whether bioaccumulation tests with single exposure routes and single organisms can predict bioaccumulation in a complex but more realistic scenario such as a mesocosm.…”

Warding off freshwater salinization: Do current criteria measure up?

“…The alternative is to base thresholds on ecotoxicological data. Single species tests have a role, particularly when protecting economically‐important or keystone species but the trend, in recent years, has been toward using information from many species (e.g., Kefford et al, 2023). In particular, broadly applicable thresholds can be set using species sensitivity distributions (SSDs: Figure 6).…”