Abstract
Freshwater species are highly impacted by human activities and the consequences on ecosystem functioning are still not well understood. In the literature, a multitrophic perspective appears to be key to advance future biodiversity and ecosystem functioning (BEF) research. This paper aims at studying indirect effects of the synthetic hormone 17α-ethinylestradiol (EE2) on a freshwater food web by creating BEF links, through the interpretation of seasonal cycles and multitrophic interactions. An ecosystem model previously developed using experimental data from a unique whole-ecosystem study on EE2 was extended with the addition of Chaoborus, an omnivorous insect. During the experimental study, a collapse of fathead minnow was measured after one year of exposure. The simulation results showed that EE2 indirect effects on other fishes (horizontal diversity) and lower trophic levels (vertical diversity) were connected to multitrophic interactions with a top-down cascade effect. The results also demonstrated that adding an omnivorous, mid-trophic level group such as Chaoborus enhances resilience. Conversely, missing such a species means that the actual resilience of an ecosystem and its functioning cannot be properly simulated. Thus, the extended ecosystem model offers a tool that can help better understand what is happening after environmental perturbations, such as with EE2.
Highlights
Pharmaceuticals and hormones are continuously entering the environment through release from wastewater treatment plants (WWTPs)
The results presented in this paper will support the transition of BEF from a description of patterns to a predictive science [16], which can help better understand the link between biodiversity and ecosystem functioning in the context of Ecosystem-based management (EBM)
During the global sensitivity analysis of Chaoborus, significant effects on zooplankton were only source for predators and copepods could grow until their bloom was done
Summary
Pharmaceuticals and hormones are continuously entering the environment through release from wastewater treatment plants (WWTPs). E1 and E2 and the synthetic 17α-ethinylestradiol (EE2) being the second most studied (35.3%) Both the natural and synthetic hormones were previously identified as the main substances responsible for estrogenic activities in WWTPs, with concentrations as low as ng/L, sometimes exceeding their predicted no-effect concentrations (PNECs) for ecological toxicity [3]. Species responses to these environmental estrogens vary considerably, with fishes having much higher sensitivities than invertebrates [4,5]. Indirect effects on tolerant species, mediated by ecological mechanisms, may appear in the environment but cannot be measured by single species laboratory-based toxicity tests; this is why population, community or ecosystem level studies are required [6]
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