Functional roles of microorganisms and microbial parasites (viruses, bacteria, chytrids and protists) in the pelagic food web

Microbes play key roles in the functioning of our lakes. Viruses (phages and eukaryotic viruses) and bacteria (among which bacterial predators of other bacteria) have been the focus of our research for several years and still represent key components of interest. Recent insights into aquatic diversity revealed a multitude of overlooked taxonomic groups mainly among protists (i.e. fungi, SAR, cryptomycota…) carrying an enormous related potential for ecological functions. These microorganisms can affect ecological processes such as organic matter transfer, trophic upgrading, and nutrient cycling. This has inspired recent efforts to add such groups to aquatic food webs, which have otherwise focused on predation, herbivory and bacterivory. In particular, microbial parasites such as fungi and fungal-like organisms are major infectious agents in pelagic ecosystems and also can be novel food sources that sustain consumer growth. Similarly, parasites can affect host population dynamics and predator-prey interactions. Our current research aims at elucidating the role of this planktonic diversity until now largely overlooked : their ecological interactions with other organisms (mainly phytoplankton and zooplankton) and the underlying mechanisms governing ecosystem processes and resilience to stress.