Grant: Discovery Grants Program - Individual

Heterotrophic bacteria play a major role in the functioning of all aquatic systems. Planktonic bacteria are responsible for much of the nutrient cycling, for the transformation and degradation of organic matter and for a significant portion of the total energy flux in these ecosystems. While we now have a relatively good idea of the broad patterns in microbial carbon and nutrient metabolism in aquatic ecosystems, and of the environmental factors that shape them, we still do not understand how these patterns are actually generated. For example, we still do not know to what extent changes in community metabolism observed in lakes and other systems are the result of the activation and inactivation of coexisting bacterial groups, or to the replacement of existing groups by others with different intrinsic metabolic capabilities. This represents a major gap in our current understanding of the functioning and regulation of aquatic microbial communities. The central goal of the proposed research is to establish the physiological and phylogenetic basis of the patterns in community carbon metabolism in planktonic bacterial communities along environmental gradients and especially in transition zones and ecotones. The proposed research combines advanced techniques in molecular ecology, single-cell approaches based on flow cytometry and cell-sorting, metabolic measurements at the community level, and organic carbon biogeochemistry. The sampling approach will be dynamic, focusing on how these microbial communities change and react as they move along entire watersheds, and across critical interfaces and major environmental features. The long-term goal of this program is to bridge the major gap in our understanding of the links that exist between bacterial community metabolism, composition and the physiological structure of the community, and how these in turn influence biogeochemical function in aquatic ecosystems. This research will advance our basic understanding of the functioning of aquatic ecosystems, but it also has major implications to broader questions in Ecology and Evolution concerning the links between diversity and ecosystem function, current topics of intense research and debate.