Grant: Discovery Grants Program - Ship Time

Microbes are involved in an overwhelming variety of biogeochemical processes. In the perennially hypoxic St. Lawrence Estuary (SLE), they control organic matter (OM) degradation through respiration processes and thus oxygen levels in the different compartments of the ecosystem. They could also play a major role in the long-term preservation of OM in sediments. However, because of the complexity of the processes at play, identifying the microbial contributions to the cycling of OM and the compartments in which they are most active is not an easy task. Questions regarding the understanding of the biogeochemical processes controlling the long-term health of the SLE converge on a better understanding of the role of microbes in the redox conditions characterizing this system and in OM preservation in the sediments. The ship time requested in this application will allow a team of researchers sharing common scientific interests and a highly complementary expertise to (i) constrain microbial processes controlling OM cycling and dissolved O2 concentrations in the waters and sediments of the SLE, and (ii) quantify the bacterial bio- and necromass and assessing their contributions to long-term OM preservation in the sediments. An array of complementary biogeochemical assays and techniques will be used to map the abundance and diversity of microbial communities, as well as bacterial production/respiration and nitrification/denitrification rates, in the water column, the bottom nepheloid layer and the sediment. These methods, belonging to the specialized fields of microbiology, molecular biology, inorganic and organic geochemistry, will be applied to dissolved and particulate material. Water samples and sediment cores (box and long piston) will be collected in the Upper and Lower SLE between Quebec and Ste-Anne-des-Monts, as well as in the Saguenay Fjord.