Degradation and recovery of protistan parasite communities under multiple stressors
The view of healthy ecosystems as being rich in parasites was largely derived by studies of parasites that require multiple hosts to complete their lifecycle (heteroxenous). In degrading environments one or more of the different hosts would be knocked out as stressor intensities increase, with the heteroxenous parasites subsequently shadowing this loss by being knocked out themselves; in subsequent recovering environments re-establishment of the diversity of heteroxenous parasites would follow the initial re-establishment of all involved hosts. On the other hand, in degrading environments parasites that can require just a single host to complete their lifecycle (monoxenous) would potentially increase in their diversity and abundances as their host become unable to prevent infection in the face of increasing stressors; in subsequent recovering environments fewer and less abundant monoxenous parasites would be able to infect their healthier hosts.
This project will not only analyse differences between heteroxenous and monoxenous protistan parasites, but also between protistan parasites that can rely on multiple host (generalists) or just one host (specialists) during a lifecycle stage, and between protistan parasites that can live most of their lives within (internal) or outside (external) of their host(s). Analysing these different aspects will give rise to a more nuanced and accurate view of the asymmetrical response of protistan parasites to environmental stressors in water quality.
The protistan parasites that will be targeted include not only the Microsporidia, which have been shown to be excellent bioindicators in aquatics ecosystems, but also the Apicomplexa, Chytridiomycetes, Oomycetes, and the Vampyrellida. A complementary combination of molecular (metabarcoding of environmental samples and amphipod guts using general and specific primers sets) and morphological observations (using fluorescence probes designed using the molecular data) will be employed to test how protistan parasite diversity, and their infection rates in animals and other protists, respond to environmental degradation and recovery under multiple stressors in the two experimental systems and in the correlative field studies. Results from this first phase of RESIST will be used in subsequent phases to target the genomes and transcriptomes of the main protistan parasite players while they are experiencing multiple stressors, and to further clarify the assignments of their functional traits and ecological performances.