Integrating bacterial metabolism as a key modulator of the response of aquatic ecosystems to human disturbances

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Freshwater ecosystems are biogeochemical hotspots embedded in theterrestrial landscape that undergoes rapid human-driven changes such asagriculture and urbanization. Central to this role are the metabolic activitiesof heterotrophic bacteria, which are responsible for most of the degradationand mineralization of the organic matter (OM) transiting in inland waters inaddition to providing nutrients and energy to the aquatic food web. Despite therecognition of this role at the ecosystem level, little is known about how andto which extent anthropogenic disturbances may alter the metabolism andfunctioning of aquatic microbial communities through changes in the amount,chemical character, and age of the OM delivered to surrounding waters.Conducting research at the interface of microbial ecology and aquaticbiogeochemistry, I propose to further our understanding of the links existingbetween microbial metabolism and the molecular properties of OM acrossperturbation gradients to better understand and predict the overall ecosystemicresponse of inland waterbodies to human activities. The main objectives of myresearch program are to: (i) identify the organic molecules released into theaquatic interface along gradients in land-cover from forested landscapes toagriculture and urban areas, (ii) assess the microbial strategies involved inthe uptake of the mobilized organic pool by human activities, and (iii)determine the metabolic response of aquatic bacterial communities alongperturbation gradients. Relying on state-of-the-art technics in analyticalchemistry and unique experimental approaches, my research program will combinetemporal and spatial field-based surveys in the Mauricie region of Québectaking advantage of the large gradient in anthropogenic influence present in this region, as wellas laboratory assays shedding light into the bacterial strategies of resourceutilization in representative impacted systems. This program represents acrucial step towards an integrative understanding of how human disturbance may disrupt not only the flow of elements at the land-water interface, but alsothe functioning of aquatic food webs and ecosystems. This understanding will inturn allow scientists and policy makers to forecast the response of aquaticecosystems and food webs to human pressure and to direct the most pressingrestoration efforts in impacted watersheds.