current projects
Arctic greenhouse gas fluxes
The high Canadian Arctic, including Tuktoyaktuk, is affected by coastal erosion, sea level rise and permafrost thaw due to climate change. Permafrost contains vast amounts of labile organic matter, which is available for microbial degradation upon thaw. These degradation processes result in CO2 and CH4 production. However, we know little about the controls and pathways of OM degradation, especially in heterogenous coastal environments. The goal of this project is to develop a simple and inexpensive proxy method to determine greenhouse gas (GHG) fluxes from the Arctic. We use incubations and geochemical analyses to predict potent biogenic GHG fluxes on regional scales and enhance our understanding of Arctic biogeochemical cycles.
project student lead: Alexie Roy-Lafontaine
St Lawrence hypoxia
Persistent hypoxia in the St. Lawrence is a growing concern for benthic and pelagic macrofauna. In addition, sediments undergo profound biogeochemical changes that affect the exchange of nutrients, metals, and carbon fluxes with the water column. Yet, fundamental questions remain unanswered about the role of sedimentary redox-active elements in consuming water column oxygen and how their behavior will change when bottom waters transition from hypoxic to anoxic conditions. Sulfate anions are abundant in seawater and supply oxidant to the seafloor, well below depths reached by dissolved oxygen and other oxidants such as manganese and iron. However, as these other oxidants become consumed, sulfate becomes increasingly important and is responsible for a large part of organic matter remineralization in the sediments. This project aims at untangling changes in the sedimentary sulfur cycle in the past century to investigate whether the products of sulfate reduction can be used to trace the evolution of hypoxia and predict the response to changing bottom water chemistry. We investigate these questions using sequential extractions of sulfur species coupled with stable isotope analysis.
project student lead: Gwenn Duval
St Lawrence thermal history
The highly productive St. Lawrence Estuary has lost about 50% of its oxygen between the 1930s and 2000s, a trend that is expected to exacerbate in the future. In addition to nutrient pollution, this oxygen loss is also caused by changes in the regional circulation pattern induced by warming ocean temperatures. To better predict the future response of the St. Lawrence system to ongoing environmental change, we need to understand the system’s natural variability and resiliency to past climatic changes. In this project, we use different molecular sea surface temperature proxies to reconstruct the role of circulation changes in the St Lawrence Estuary and Gulf of St Lawrence.
project student lead: Marie Engel
Lake Untersee
Lake Untersee, Queen Maud Land, Antarctica is a perennially ice-covered lake which features extreme chemical gradients and macroscopic microbial structures that have been absent from the geological record for billions of years. This makes Lake Untersee an important site to understand early Earth’s history and to better understand how life has emerged on our planet and spread in our oceans. In this project, we investigate the microbial metabolisms active in the lake, how the exclusion of animals influences biogeochemical cycling, what we can discern about Earth’s primordial environments, and how this sensitive environment reacts to climate change.
project student lead: Daniel Fillion
The fate of stranded seaweed OM
The accumulation of stranded macroalgae in beach tidelands is critically important for nutrient recycling, trophic connectivity and coastal ecosystem functioning. These macroalgae are hotspots of metabolic activity and greenhouse gas (GHG) production through microbial decomposition. Little is known about the bacterial communities involved in macroalgal decomposition and their effects on GHG emissions. We seasonally monitor the decomposition/remineralization of stranded seaweed as well as the quality of the organic matter of and GHG emissions from wreck in the St. Lawrence system to quantify changes in respiration and the composition of the bacterial community and fauna involved in organic matter fragmentation and decomposition processes.
project student lead: Tommy-Loup Bordeleau
Alkenone ‘evolution’ in the Arctic
Haptophyte algae are important phytoplanktonic primary producers in the ocean and in lakes. Within this group, members of the Isochrysidales produce characteristic molecules (long-chain alkenones) that preserve in sediments for million years and can be used to infer environmental conditions in the past, including sea surface or lake surface temperatures. At present, temperature is a major control on the alkenone fingerprint of Isochrysidales and one of the most robust sea surface temperature proxies is based on this observation. However, other environmental parameters such as salinity and stratification also determine the presence and diversity of haptophytes and evolutionary controls on sedimentary alkenone distributions are poorly understood. Species diversification may have led to alkenone diversification in the past. We combine lipidomic and metagenomics tools to investigate environmental and evolutionary controls on haptophyte assemblages in the Canadian Arctic. Our work is crucial to establish unbiased paleotemperature records, understanding past Arctic climate dynamics, and inform global climate models.
project student lead: Laury-Ann Dumoulin
St Lawrence paleo redox
To better predict the future response of the St. Lawrence system to ongoing environmental change – specifically its unprecedented loss of oxygen in recent decades – it is imperative to understand the past redox evolution of the St. Lawrence system. Past episodes of hypoxia or anoxia serve as models of the current change. In this project, we use microbial biomarkers to spatio-temporally trace oxygen limitation in the St Lawrence Estuary and Gulf of St Lawrence. These data will help us to characterize the response of the system to different environmental controls, map its natural variability, and assess its resiliency to past climatic changes.
project student lead: Daphnée Laliberté
International brGDGT round robin
We participate in the on-going international brGDGT round robin study. Organized by our colleagues at ETH Zürich and Utrecht University, we aim at assessing the compatibility of brGDGT proxies between labs. BrGDGTs (short for branched glycerol dialkyl glycerol tetraethers) are bacterial membrane lipids used to infer environmental conditions such as temperature and pH. Assuring compatibility and reproducibility of paleo-environmental information is key to having a robust understanding of the evolution of Earth’s climate and biogeochemical cycles.