Abstract
Freshwaters are increasingly exposed to complex mixtures of pharmaceutical and personal care products (PPCPs) from municipal wastewater, which are known to alter freshwater communities' structure and functioning. However, their interaction with other disturbances and whether their combined effects can impact ecological resilience (i.e., the ability of a system to tolerate disturbances without altering the system's original structure and processes) remain unexplored. Using in situ mesocosms in 2 lakes with different nutrient levels (mesotrophic and eutrophic), we assessed whether a pulse exposure to sublethal concentrations of 12 PPCPs affects the ecological resilience of natural phytoplankton communities that experienced an abrupt environmental change involving the destabilization of the water column through mixing. Such mixing events are predicted to increase as the effects of climate change unfold, leading to more frequent storms, which disrupt stratification in lakes and force communities to restructure. We assessed their combined effects on community metrics (biomass, species richness, and composition) and their relative resilience using 4 indicators (cross-scale, within-scale, aggregation length, and gap length), inferred from phytoplankton communities by discontinuity analysis. The mixing disturbance alone had negligible effects on the community metrics, but when combined with chemical contaminants significant changes were measured: reducing total biomass, species richness, and altered community composition of phytoplankton. Once these changes occurred, they persisted until the end of the experiment (day 20), when the communities' structures from the 2 highest exposure levels diverged from the controls. The resilience indicators were not affected by PPCPs but differed significantly between lakes, with lower resilience found in the eutrophic lake. Thus, PPCPs can significantly alter community structures and reinforce mechanisms that maintain ecosystems in a "degraded state." Environ Toxicol Chem 2019;38:2197-2208. © 2019 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals, Inc. on behalf of SETAC.
Highlights
The growing diversity of pharmaceuticals and personal care products (PPCPs) found in freshwaters is of concern because these substances have the potential to negatively impact biota, both individually and in mixtures (Loos et al 2009).Recent studies (Lee et al 2016; Pomati et al 2017; Rosi et al 2018) have shown that sublethal exposures to PPCPs can alter the community structure of aquatic communities including phytoplankton, bacteria, and macroinvertebrates, the sensitivity of species to these pollutants varies considerably (Blanck 2002)
Though the present study provides insights on the ecological effects of PPCP pulse exposure, the need for long‐term continuous exposure scenarios in combination with multiple stressors persists because PPPCs are being continuously released into the environment (Richmond et al 2017)
Our results showed that the effect of a single pulse of PPCP superseded the effects of a single mixing disturbance on community structures, whereas the resilience indicators of phytoplankton communities were found to be only marginally affected by both stressors
Summary
The growing diversity of pharmaceuticals and personal care products (PPCPs) found in freshwaters is of concern because these substances have the potential to negatively impact biota, both individually and in mixtures (Loos et al 2009).Recent studies (Lee et al 2016; Pomati et al 2017; Rosi et al 2018) have shown that sublethal exposures to PPCPs can alter the community structure of aquatic communities including phytoplankton, bacteria, and macroinvertebrates, the sensitivity of species to these pollutants varies considerably (Blanck 2002). The growing diversity of pharmaceuticals and personal care products (PPCPs) found in freshwaters is of concern because these substances have the potential to negatively impact biota, both individually and in mixtures (Loos et al 2009). Freshwater ecosystems respond to many other factors and processes of both natural and anthropic origins, many of which occur as pulse disturbances (e.g., storms, intense runoff events, spills and overflows of untreated wastewater; Bender et al 1984). Climate scenarios for Europe predict increased occurrences of droughts, floods, and storms (Beniston et al 2007). An increase in the frequency of stormy events will promote mixing wileyonlinelibrary.com/ETC
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