Life in a contaminant milieu: PPCP mixtures generate unpredictable outcomes across trophic levels and life stages

Abstract

Nearly all aquatic ecosystems are affected by sublethal levels of anthropogenic chemical contamination, but other agents of large‐scale anthropogenic disruption of ecosystems have received more attention. Consequently, ecologists do not fully appreciate how sublethal contaminant exposure affects ecosystems. Sublethal contaminants can affect ecological systems directly via their impacts on an organism's fitness or indirectly by changing the strengths of species interactions. This study investigated how an emerging class of contaminants—pharmaceuticals and personal care products (PPCPs)—influences food webs by affecting the biology of organisms and by interfering with predator–prey interactions. Specifically, we investigated how three common PPCPs—caffeine, DEET (N, N‐diethyl‐meta‐toluamide), and triclosan—affect the strength of the interaction between a common mosquito predator (i.e., mosquito fish) and mosquito larvae as well as how these PPCPS affect mosquito survival, life history traits, and oviposition site choices. We found that all three PPCPs, individually and combined as a mixture, reduced predator consumption rates. Relative to a contaminant‐free control, the presence of predator cues reduced mosquito oviposition and larval abundance for all PPCP treatments except for DEET. Predator cues reduced mosquito adult emergence across PPCP treatments; however, mosquitoes that were exposed to caffeine did not emerge as adults even in the absence of predator cues. This study shows that the effects of PPCPs are diverse and can interact with mosquitoes and their predators in ways that cannot be predicted by their individual effects. In a contaminated world, ecologists need to better understand how sublethal concentrations of ubiquitous, biologically active pollutants might challenge what we think we know about how ecological systems function.

Environmental Risks of Pharmaceutical Mixtures in Aquatic Ecosystems: Reflections on a Decade of Research

“…Community‐level and/or meso‐ or microcosm studies with multiple species have been done to track the effects of API mixtures on survival, biomass, biodiversity, and richness across trophic levels (Pomati et al, 2017; Roose‐Amsaleg et al, 2021). Though not with APIs, Parrish et al (2019) showed that density‐dependent processes that regulate predator–prey dynamics among mosquitofish (predator) and mosquito larvae (prey) were differentially affected by exposure to individual PPCPs (caffeine, diethyltoluamide, and triclosan) and their mixture. In addition, environmental DNA has been used to investigate the influence of binary PPCP mixtures on bacterial ecological functions (e.g., denitrification and ammonium oxidation) in river sediment (Xu et al, 2020).…”

Multi-compartment impact of micropollutants and particularly antibiotics on bacterial communities using environmental DNA at river basin-level

“…Synthetic organic chemicals are typically present at low environmental concentrations in the aquatic environment (pg/L to ng/L) and are therefore often called micropollutants (Schwarzenbach et al, 2006). Micropollutants often have deleterious effect at different trophic levels (Beketov et al, 2013; Burdon et al, 2020; Kidd et al, 2007; Parrish et al, 2019) and levels of biological organisation (Inostroza et al, 2016; König et al, 2017; Weichert et al, 2020) due to their high biological activity (Stamm et al, 2016).…”