Pharmaceuticals: An Overlooked Source of Pollution for Wildlife?

Title: Pharmaceuticals: An Overlooked Source of Pollution for Wildlife?

PhD supervisors
Sabrina Tartu, Associate Professor – François Brischoux, Research Director

Project Description
Following World War II, the pharmaceutical industry experienced rapid growth and greatly contributed to increasing life expectancy. Pharmaceuticals serve numerous purposes, including “establishing medical diagnoses, treating or preventing diseases, and restoring, correcting, or modifying physiological functions.” Global pharmaceutical consumption continues to rise due to both human population growth and ageing, as well as the intensification of agriculture and the widespread use of veterinary drugs. After ingestion, these substances are excreted through urine and faeces and subsequently transferred to aquatic and terrestrial ecosystems via wastewater, sewage sludge spreading from wastewater treatment plants (WWTPs), and manure application. Concerns regarding the presence of pharmaceuticals in the environment have been raised for several decades because most of these compounds are biologically active. Consequently, wildlife is continuously exposed to a wide range of substances capable of altering physiological processes.
Freshwater ecosystems harbour high levels of biodiversity and support numerous ecological processes and functions traditionally associated with water quality maintenance and soil erosion prevention. However, these ecosystems are under intense anthropogenic pressure, and pharmaceuticals now constitute a major proportion of urban pollutant loads in aquatic environments. Amphibians are among the aquatic organisms likely to be affected by this type of pollution. With 40.7% of species classified from “Vulnerable” to “Critically Endangered,” amphibians represent the most threatened class of vertebrates, and environmental pollution is considered one of the major causes of this decline. In most amphibian species, embryonic and larval development includes an obligatory aquatic phase, meaning that embryos and tadpoles are continuously exposed to waterborne contaminants. Exposure to endocrine-disrupting compounds may even reverse genetic sex. Amphibian skin remains highly permeable throughout life, facilitating the absorption and bioaccumulation of potentially harmful substances. Depending on the species, adult amphibians may exhibit lifestyles ranging from fully aquatic to predominantly terrestrial. Therefore, species with strong aquatic dependence, such as the African clawed frog, Xenopus laevis, are particularly relevant for studying the effects of pharmaceutical exposure. Because of its aquatic lifestyle, Xenopus are exposed to pharmaceuticals throughout its entire life cycle.
Xenopus laevis is an invasive alien species on four continents. In France, following an accidental introduction in the late 2000s in northern Deux-Sèvres (department 79), its distribution has progressively expanded into neighbouring regions. Although its distribution remains limited at the national scale, Xenopus is a laboratory model for endocrine disruption studies, and its hormonal mechanisms are extensively documented. This makes it a highly relevant model species for investigating endocrine disruption under natural conditions.
PhD Objectives: The first objective of this PhD project will be to characterize aquatic pharmaceutical pollution. The second objective will be to determine whether this type of pollution affects several biomarkers of interest in exposed amphibians, including steroid hormones, gut microbiota and plasma metabolome. Finally, the third objective will be to validate relationships observed in natural environments under controlled experimental conditions. This will involve a low-dose mixture (“cocktail effect”) experimental approach in order to establish causal relationships.

Doctoral Research Program
-Literature review
-Field sampling of wildlife and environmental matrices
-Laboratory analyses (ELISA, DNA extraction, NGS library preparation)
-Statistical analyses
-Mandatory and optional training courses
-Dissemination and promotion of research findings (scientific publications, national and international conferences, public outreach)

Timeline
The first year will primarily focus on fieldwork and in natura sample collection. The second year will be dedicated to laboratory analyses and experimental work. The third year will be dedicated to analyses and writing. An optional second field season may take place during the third year.

Candidate Profile
-Master’s degree in ecotoxicology, ecophysiology, or related disciplines
-Strong interest in animal experimentation, laboratory analyses, and bioinformatics
-Proficiency in the statistical software R
-Excellent written and spoken scientific English

Application
Applicants must submit a curriculum vitae, a cover letter directly related to the PhD topic, academic transcripts for both years of the master’s degree and the names of two referees.
Applications should be sent to sabrina.tartu@univ-lr.fr and francois.brischoux@cebc.cnrs.fr

Contract-Specific Information
During fieldwork and experimental periods, work outside regular working hours (i.e., evenings and/or weekends) will be required.
The PhD student will be based at the CEBC, a research laboratory located in a rural area. The nearest major cities are Niort (30 km) and La Rochelle (70 km).
Funding has already been secured.