Grant: Discovery Grants Program - Individual

Bacteria play a major role in the functioning of all aquatic systems. Planktonic and benthic bacteria are responsible for much of the nutrient cycling, the transformation and degradation of organic matter and for a significant portion of the total energy flux in these ecosystems. One of the key challenges in contemporary microbial ecology has been to understand the factors of structure these functionally complex and extremely diverse communities. For aquatic bacterial communities, this implies understanding the origin of the microbes that we observe, their movement within the interconnected aquatic network, and their responses to the various environmental conditions that they encounter during transit. Most current studies lack this dynamic, network context, and therefore offer a fragmented and partial perspective of aquatic bacterial community assembly. Here I propose a program that will explicitly take a whole network approach to exploring bacterial community assembly, where we will reconstruct the taxonomic, metabolic and functional microbial successions that occur along the aquatic continuum, from soils to the sea through interconnected rivers and lakes, and identify the main underlying drivers. We will in parallel assess the chemical succession that occurs in the molecular structure and reactivity of the dissolved organic carbon pool (DOC) along this aquatic continuum, with the objective of determining the connections and interactions that may exist between these two key components of all aquatic ecosystems. This integrated watershed perspective of aquatic bacterial communities and organic C biogeochemistry was technically and financially unthinkable only a few years back, but is now enabled by new generation approaches that have increased our capacity of assessing the structure of both bacteria and DOM with unprecedented detail and at a fraction of the cost. The proposed program will benefit from an ongoing research platform that will provide a large-scale, integrated sampling of rivers, wetlands and lakes along the entire aquatic continuum in a large boreal watershed of Québec. We will carry out highly spatially resolved sampling along this continuum, and will apply a combination of high-throughput sequencing and genomic microarray technologies, metabolic and physiologic measurements of bacterial communities, and advanced analytical approaches to characterize the molecular composition of DOC. The proposed work is a logical expansion of the research that our group has done over the past decade, and will establish the foundation for understanding the assembly of both bacteria and organic pools within complex aquatic networks, their respective environmental controls, and the possible links that exist between them. The research will likely lead to a reassessment of current models and paradigms of bacterial succession, community assembly and links to resources.