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 the*terrestrial landscape that undergoes rapid human-driven changes such as*agriculture and urbanization. Central to this role are the metabolic activities*of heterotrophic bacteria, which are responsible for most of the degradation*and mineralization of the organic matter (OM) transiting in inland waters in*addition to providing nutrients and energy to the aquatic food web. Despite the*recognition of this role at the ecosystem level, little is known about how and*to which extent anthropogenic disturbances may alter the metabolism and*functioning 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 aquatic*biogeochemistry, I propose to further our understanding of the links existing*between microbial metabolism and the molecular properties of OM across*perturbation gradients to better understand and predict the overall ecosystemic*response of inland waterbodies to human activities. The main objectives of my*research program are to: (i) identify the organic molecules released into the*aquatic interface along gradients in land-cover from forested landscapes to*agriculture and urban areas, (ii) assess the microbial strategies involved in*the uptake of the mobilized organic pool by human activities, and (iii)*determine the metabolic response of aquatic bacterial communities along*perturbation gradients. Relying on state-of-the-art technics in analytical*chemistry and unique experimental approaches, my research program will combine*temporal and spatial field-based surveys in the Mauricie region of Québec*taking advantage of the large gradient in anthropogenic influence present in this region, as well*as laboratory assays shedding light into the bacterial strategies of resource*utilization in representative impacted systems. This program represents a*crucial step towards an integrative understanding of how human disturbance may disrupt not only the flow of elements at the land-water interface, but also*the functioning of aquatic food webs and ecosystems. This understanding will in*turn allow scientists and policy makers to forecast the response of aquatic*ecosystems and food webs to human pressure and to direct the most pressing*restoration efforts in impacted watersheds.