Within the framework of the Master research programmes funded by the Fondation pour la Recherche sur la Biodiversité (FRB), we are looking for a candidate for a project at the nexus of biodiversity (microbial ecology) and health (epidemiology of amphibian infectious diseases). The successful candidate will join our GloMEc (Global Change in Mountain Ecosystems) and BIOREF (Biodiversity, trophic networks and flows in aquatic ecosystems) team at the Functional Ecology and Environment Laboratory (UMR 5245) in Toulouse.
Mountain ecosystems are of paramount importance for human societies (e.g. provision of drinking water) but very sensitive to global change (climate change, pollution, habitat degradation, introduction of non-native species) caused by human activities. Biofilms are very productive and diverse communities in such freshwater ecosystems. At high elevation, they form the basis of food webs and serve many other roles. While biofilms are also impacted by global change, the consequences of this are unknown. Amphibians play an active role in water purification and form the link between the aquatic and terrestrial ecosystems. Amphibian chytridiomycosis, a panzootic disease caused by the aquatic fungus Batrachochytrium dendrobatidis (Bd), is a serious threat to amphibian biodiversity, having caused hundreds of declines and extinctions worldwide. This disease is observed in the Pyrenees since 2003, where it causes mass mortalities in populations of the common-midwife toad (Alytes obstetricans).
The epidemiology of amphibian chytridiomycosis is not yet elucidated. There is evidence to suggest that amphibians may be protected by biotic environmental factors, such as aquatic microfauna (Schmeller et al. 2014). Our aim is to assess whether benthic biofilms in Pyrenean lakes can reduce the infectious risk posed by Bd. We also want to determine whether different types of biofilms have different protective capacities, and whether they can help limit infection. Indeed, Bd has an aquatic, motile life stage, the zoospore (the infective stage), which are in contact with benthic biofilms. The latter are mini-ecosystems known either to be able to harbour and protect certain human pathogens causing waterborne diseases (when the latter manage to colonise a biofilm), or to eliminate them (biofilms can harbour micropredators, or contain microorganisms antagonistic to Bd, for example by secreting antifungal substances). Our hypothesis is that the greater the biodiversity in the biofilms, the higher the probability that they will be controlling zoospores numbers in the water column, thus decreasing the infection pressure on amphibians. The alteration of biofilms by human activities may then lead to a higher risk of infection and/or parasite load for amphibians.
To test this hypothesis, we have adopted a transdisciplinary approach, linking in- and ex-situ investigations. With this M2 project, we complement our meta-barcoding approach with laboratory experiments. We intend to analyse whether these biofilms alone can reduce the number of Bd zoospores and if this reduces the infection pressure on tadpoles. In combination, our two approaches will enhance our understanding of the role of biofilms in driving disease dynamics.
The approach is multidisciplinary, involving epidemiological, ecological (limnology) and microbiological sciences. The scale is regional (Pyrenees).