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Using FREshwater organisms to MItigate the pathogen Batrachochytrium dendrobatidis

Periodic Reporting for period 1 - FreeMi (Using FREshwater organisms to MItigate the pathogen Batrachochytrium dendrobatidis)

Reporting period: 2015-06-01 to 2017-05-31

Amphibians are currently the most threatened vertebrates on the planet. Their declines have many causes, from overharvesting to habitat destruction. Chytridiomycosis, the disease caused by the emerging fungal pathogen Batrachochytrium dendrobatidis (Bd), has been identified as a major driver of amphibian declines worldwide. However, to date, no efficient disease mitigation strategy is available to protect amphibians against Bd in nature. The global loss of amphibians through fatal outbreaks of chytridiomycosis has catastrophic long-lasting consequences for the functioning of ecosystems, as amphibians are keystone species in many habitats. They impact nutrient dynamics, influence the cycling of energy flows between freshwater and terrestrial systems and control populations of pest insects. It is therefore of paramount importance for ecosystem functioning to develop and implement disease mitigation strategies for the conservations of amphibians. The main scientific objective of the project FreeMi was to pave the road to the development of a safe and effective mitigation strategy targeting Bd at the habitat level, by natural augmentation of zooplankton able to consume zoospores of Bd and to lower the risk of infection of the amphibian hosts. The main training objective of the project FreeMi was to move from pure fundamental research to more applied research by training-through research, take more responsibilities in management and leadership, and make my work and my expertise more visible to the academic researchers, in order to reinforced my position in the scientific community and improve my career opportunities for the future.
FreeMi investigated how zooplankton community are able to protect amphibians against Bd and found that species richness is the best indicator of a site’s potential to Bd infection, a knowledge that will help predicting further colonisation of new sites by Bd. FreeMi also identified the local species that are the most efficient at consuming Bd zoospores and established a list of species to be included in the biological control tool, by screening species-specific capacity over more than 75 zooplankton species. Then, good candidate species to be included in the biocontrol were isolated and cultivated in the laboratory, at low cost, with non-sophisticated equipment and limited space. The impacts of the environmental conditions (community, density of zoospores and temperature) on consumption efficiency were also assessed and, generally, these parameters did not strongly impact the efficiency of the biocontrol tool. Finally, FreeMi developed a framework for the development of a zooplankton bioncontrol of Bd, with the aim that the approach developed by FreeMi can be followed and applied worldwide. This framework and the results obtained by the project are and will be disseminated to conservationists and stakeholders. FreeMi also identified crucial points that need to be acknowledged and addressed for a successful bioaugmentation strategy: 1) understanding of the dynamics of zooplankton, as the zooplankton community undergoes a steady change over a season, and 2) the disturbances which altered the zooplankton communities need to be identified and controlled before the biocontrol can be applied.
The work carried out by FreeMi is entirely new and innovative. It addressed issues related to the environment by better understanding the parameters related to the colonisation success of a wildlife pathogen. It will help predicting the colonisation potential of a given site and proposes actions to be implemented to protect this site against the pathogen. Because amphibians play an important role in the functioning of ecosystems, the biocontrol developed during the course of the project can help halting the global loss of amphibians through fatal chytridiomycosis outbreaks and bring important benefits for the society by addressing the conservation of amphibian species and the consequences of amphibian loss on ecosystem functioning. The major output of FreeMi, i.e. the framework for using bioaugmentation to mitigate adverse effects of Bd, is a new product and service to the society, to non-academic stakeholders and actors in conservation biology, in the mitigation of Bd worldwide.

Although safe biological control tools are challenging to develop, many of them have successfully contributed to the protection of the flora and the fauna of natural ecosystems and are presently a key component in many recovery plans, as well as management of agricultural pests. The new knowledge acquired by FreeMi is therefore of tremendous importance for other pathogens in other ecosystems and in the industry. Indeed, many cultivated algae and animals produced in aquatic farms suffer from zoosporic fungi in both freshwater and marine systems. Therefore, the framework developed by FreeMi will be useful to develop similar biocontrol against these fungi leading to considerable economic losses in aquaculture industry producing food, food supplements, biofuels and pharmaceuticals.
Dr. Adeline Loyau during field work
Project's flyer
FlowCam - automatic fluid image analyser