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Empirical data collection along a gradient of productivity in the Labrador Sea took place aboard the oceanographic vessel CCGS Hudson.

These data allowed to characterize the relationships between DOM compounds, metabolism and prokaryotic diversity by structuring prokaryotic communities using spatial distribution of abundance (SpAD) modeling.

SpAD modeling empowers the exploration of large amounts of information at
large spatial scales.

The use of SpAD modeling has led to the development of a conceptual framework for how environmental conditions, microbial community structure, and ecosystem functions interact at different scales.

The ultimate goal is to better understand how carbon and nutrients are exchanged in aquatic ecosystems.

Expertise: Modeling, conceptual framework development, molecular biology, biogeochemistry, carbon cycle

“The microbial communities living in deeper layers of the ocean might actually be better equipped to transform surface carbon into unique and more stable molecules"

The microbial carbon pump hypothesis (MCP) suggests that the successive transformation of labile dissolved organic carbon (DOC) by prokaryotes produces refractory DOC (RDOC) and contributes to the long-term stability of the DOC pool in the deep ocean.

To test this hypothesis, surface water from a deep convective region of the ocean was exposed to epipelagic, mesopelagic, and bathypelagic prokaryotic communities.

Changes in DOM concentration and composition and prokaryotic taxa were tracked over time.

Deep ocean prokaryotic taxa were more efficient at consuming DOC and producing RDOC, as evidenced by a greater abundance of highly oxygenated molecules and fluorescent components associated with recalcitrant molecules.

This first trial empirical evidence of MCP in natural waters demonstrated that carbon sequestration is more efficient in deeper waters and proved that the greater diversity of prokaryotes in the rare biosphere holds greater metabolic potential in the creation of these stables dissolved organic compounds.

Expertise: sea ​​sampling, characterization of deep eddies, microcosm, molecular biology, characterization of DOC and DOM, biostatistics

“The deoxygenation of lakes is of growing concern as it threatens the provision of ecosystem services.”

Periods of anoxia are expected to be lengthened and extended in lakes, promoting the production or release of nutrients, greenhouse gases and metals from the water column and sediments.

The accumulation of these compounds cannot be easily predicted, impeding our ability to predict the ecological consequences of global changes on aquatic ecosystems.

Using monitoring data from four lakes, I developed during this research project, a new tool, anaerobic duration, to study anaerobic processes in lake waters.

Anaerobic duration, as a single predictor, can explain 21–60% of the variation for ammonium, phosphorus, and one type of fluorophore of the dissolved organic matter.

Anaerobic duration could be modeled using only two oxygen profiles and lake bathymetry, making it an easily applicable tool for interpreting and extrapolating biogeochemical data.

This new tool therefore has the potential to transform widely available oxygen profiles into an ecologically meaningful variable.

Expertise: In situ physico-chemical parameter measurements, modelling, biostatistics, chemical analyzes (soluble reactive phosphorus and ammonium)