Contacts

I am studying the role of Fe as a controlling factor of cyanobacteria dominance in harmful algal blooms. Natural abundance Fe isotopes are useful tracers for biogeochemical processes involving Fe. Within boreal shield catchments, we found the range of iron isotopes spanned more than half of the entire range of Earth surface samples. We studied two lakes: eutrophic Lake 227 with experimental fertilization and oligotrophic Lake 442. Within the lakes, two layers with distinct isotope compositions of dissolved and particulate Fe were observed in the water columns. In the oxic surface layer, dissolved δ⁵⁶Fe is more positive than particulates, consistent with dominance by Fe-DOC complexes. In the anoxic lower layer, upward flux from sediments dominates the dissolved Fe pool and redox processes produces isotope fractionation between dissolved and particulate Fe. The observed natural large fractionation of Fe isotopes provides a potential tool to probe acquisition of Fe by cyanobacteria and algae. Furthermore, δ⁵⁶Fe of bulk sediments in L227 clearly records the 50-year experimental fertilization regimes and currently reflects values in POM in the epilimnion, suggesting sediments could record the onset of changes in Fe cycling due to nutrient addition.

Linking the Source and Fate of Fe and DOM in Boreal Freshwaters

I am studying the interaction of DOM and Fe and how this interaction influences aquatic carbon cycling and the measurement of DOM quality. I have conducted incubation and titration laboratory experiments using samples collected from Yellowknife, NWT, Dorset, ON and the Experimental Lakes Area, ON. The aim of this research is to determine whether Fe and pH significantly influence photodegradation of DOM and measures of DOM quality using a range of natural samples.

I’m using the stable isotopes of carbon and hydrogen in methane (CH₄) to determine sources and processes affecting CH₄ release in small subarctic lakes (NWT).  CH₄ oxidation, CH₄ production pathway or temperature will affect the isotope mass ratio differently, and researchers rely on the fractionation factor to determine these discrepancies. The fractionation factor for hydrogen during CH₄ oxidation has not been widely accepted and therefore, my research aims to confirm a fractionation factor to assist in determining the role of CH₄ oxidation in controlling CH₄ emissions to the atmosphere.