The role of algal-bacterial interactions in aquatic ecosystem function

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Microbes are the essential drivers of biogeochemical cycling and carbon (energy)-flow in aquatic ecosystems. Within the context of ecosystem function, free-floating photosynthetic algae (phytoplankton) and heterotrophic bacteria (bacterioplankton) have distinct roles as primary producers and decomposers, respectively. Though often studied as autonomous functional-groups in aquatic ecosystems, algal and bacterial communities can interact in a variety of ways that are antagonistic and/or synergistic. To improve our understanding of energy flow and nutrient cycles across freshwater ecosystems, my research program will focus on the important roles of algae and bacteria as key players in aquatic ecosystem function and contaminant fate. Specifically, my research group will determine how the synergistic and antagonistic interactions between algae and bacteria mediate carbon, nutrient, and contaminant dynamics in lake systems. A series of small lakes from the "Land Between" ecotone in south-central Ontario will be the focus of our research program. The Land Between is a narrow ecological transition zone between limestone and granite-dominated bedrock along a transect from Parry Sound to Kingston in the Great Lakes Basin. The geological mosaic of the Land Between offers an ideal array of environmental gradients (i.e. pH, dissolved organic carbon, and nutrients) due to the variable physiography. As such, we will be able to directly assess the algal-bacterial communities in lakes representing a range of environmental characteristics, all within a relatively small geographic and climatic region. This research program will be the first of its kind to (1) Characterize the community structure/function of metabolically-distinct microbial groups in lakes, and (2) Show how algal-bacterial interactions influence carbon, nutrient, and contaminant dynamics in freshwater systems.