Projects in Theme 1

Theme leaders: Paul del Giorgio (Université du Québec à Montréal) and Irene Gregory-Eaves (McGill University)


Project 1.1: Carbon gas fluxes, concentration and isotopic signature in Canadian lakes
Project leader: Yves Prairie, Université du Québec à Montréal (UQAM)

Summary: Even if lakes and rivers occupy less than 1% of the globe, they collectively emit CO2 and CH4 in amounts that are of the same order of magnitude as that taken up by the other 99% (the sum of terrestrial and oceanic net uptakes. Canadian lakes and rivers represent a disproportionately large share of all inland waters of the world. Yet, because of the large diversity of the canadian landscape, there is currently no estimate of the canadian contribution to global lake emission. While we know that they are nearly all supersaturated with both carbon dioxide (CO2) and methane (CH4), their degree of oversaturation varies widely among lakes, even within a small geographical region. This is particularly true with the more complex biogeochemistry of CH4 relative to CO2. These knowledge gaps impede the development up-scaling rules­­ to estimate regional or countrywide emission rates beyond the application of simple averages. A central issue pertaining to this high variability is the origin and in situ transformation of the gases. In this project, we propose to use isotopic (13C) signatures of CO2 and CH4 in a large number of lakes from different regions to trace the probable origin (organic decomposition vs mineral weathering) and extent of transformation (e.g. CH4 oxidation to CO2) and these may be driven by regional and local features of the landscape. In addition, the project will allow us to estimate the extent to which lake CH4 emissions at the regional scale are reduced by in-lake processes and to identify the main drivers.

Project 1.2: Biogeochemical drivers of carbon sinks, greenhouse gas fluxes, and nutrient regeneration – Patterns in lake metabolism and organic C dynamics
Project leader: Paul del Giorgio, Université du Québec à Montréal (UQAM)

Summary: Ecosystem metabolism, and in particular, primary production, respiration and the balance between the two (P/R ratio), is at the core of the physical, ecological and biogeochemical functioning of lakes. In particular, lake metabolism is intimately linked to cycling of carbon and other materials, to the structure and length of trophic food webs, to the lake greenhouse has dynamics and to a host of other important lake functions. Lake metabolism in turn integrates the influence of a large suite of physical, chemical and biological lake and watershed features, and is sensitive to climate and environmental change. This component of Theme 1, Project 1(2) will quantify gross primary production, ecosystem respiration and the lake P/R balance across all Pulse lakes, and will attempt to link these to lake and landscape drivers, as well as to the amount and composition of the organic matter pools across the target lakes. We will work closely with Theme 1/ Project 1(1 and 3) teams, in order to link the patterns in lake metabolism to lake GHG emissions and C burial, and to determine the net balance of these processes.

Project 1.3: In-lake carbon modelling in Canadian lakes
Project leader: Yves Prairie, Université du Québec à Montréal (UQAM)

Summary: Canada is home to millions of lakes. Regardless of the magnitude of any sampling program, projecting the results from field measurements to larger geographic units (ecoregions, province, entire country) will require upscaling tools that will integrate both the particular geography of each lake/catchment and the biogeochemical processes occurring within each lake. In the context of lake carbon dynamics, understanding the relationships between the landscape and the lakes into which they drain is fundamental to the development of such tools. The objective of this project is to model the fate of terrestrial organic carbon export as it travels through the aquatic network and is transformed within lakes through both microbial and physical processes (photodegradation, burial, evasion). This project will use the hydrological network information, water residence time (WRT, see Vachon et al. 2016 for details on integration of WRT on degradation parameters), land cover extraction, lake water optical properties obtained from GIS reconstruction and combined with field measurements to develop models of OC processing at the whole landscape and eco-regional levels and how the reactivity of the organic matter changes as it travels through the landscape. An important contribution of this project is to estimate the reactivity parameters of the dissolved organic matter in different Canadian ecoregions.

Project 1.4: Sediment phosphorus characterization across Canadian lakes
Project leader: Helen Baulch, University of Saskatchewan

Summary: Lakes are embedded across the Canadian landscape. This landscape is incredibly heterogeneous in terms of its land cover, and underlying geology. This variation has an important influence on the character of lakes. A widespread concern is that high nutrient concentrations are leading to algal blooms – and work has been ongoing for decades to help control nutrient inputs into lakes. Within this project, we aim to understand how phosphorus is bound in lake sediments and how this varies with geology and land use, ultimately helping us to understand what proportion of this phosphorus is likely to be remobilized – contributing to ongoing problems of blooms – and what proportion will be tightly bound in the sediments over the long-term.

Project 2: Fate and behaviour of contaminants of emerging concerns in Canadian lakes
Project leader: Hubert Cabana, Université de Sherbrooke

Summary: We are interested in the study of the presence and fate of emerging contaminants (EOCs) such as pharmaceuticals, personal care products, etc., in the aquatic environment. More specifically, we want to understand how EOCs behave in surface waters once they are released in the environment, how they interact and distribute with other abiotic and biotic components of aquatic ecosystems such as particles, sediments and biota and how and in what new compounds they transform or degrade.  The project consists in the development of new analytical approaches for the detection and quantification of polar and non-polar EOCs based on using liquid chromatography coupled to both low resolution and high resolution mass spectrometry (targeted analysis; actually we are able to detect and quantify ± 80 EOCs. For the next sampling campaingns, we aim to be able to quantify ± 100 molecules). The student in charge of the project will participate in sampling campaigns and will validate its methods of analysis. The developed method will then be used by PR in order to implement that methodology for routine monitoring of these chemicals during the Network sampling campaigns. That first part of this project will give us a first overview related to the presence of the selected molecules in Canadian lakes. The picture of CEO occurrence in lakes will be improved for SC2 as we will add molecules based on the non-targeted analysis performed.

Then, for the most detected EOCs, we will determine the behavior of these chemicals in the water columns (including the solid phases). Actually, most of the actual studies dealing with the fate and behaviour of these chemicals focused on the aqueous phase, and concentrations of the EOCs in solid fraction were rarely determined partly because of the analysis challenge in these matrices and the presumption that EOCs are highly water-soluble. In that part of the project, we will determine the interactions of the EOCs between the aqueous and solid phases.

In addition, for the main CEO quantified in the studied systems, we will determine the transformation products generated by biotic and abiotic actions. These transformation products will be determined first considering the biotic transformations and then the abiotic ones (eg. phototransformation). The transformation products will be determined using non-targeted MS methodologies in order to consider all the potential candidates. We will then add the main identified products in the routine analysis.

Finally, we will used a high resolution MS methodology (eg. QTOF-MS) in order to determine the presence of initially non-targeted CEO in the water samples. To do so, reliable identification of untargeted chemicals requires both high resolving power and high mass spectral accuracy to increase selectivity against the matrix background and for a correct molecular formula assignment to unknown compounds. For the identification and structure elucidation of unknown compounds within a reasonable time frame and with a reasonable soundness, we will use advanced automated software solutions as well as improved prediction systems for theoretical fragmentation patterns. That approach will reduce the analytical bias induced by the initial analytical approach developed in order to detect and quantify targeted (known) chemicals.

Project 3: Changes in Canadian lakes over the Anthropocene; which lakes are susceptible to different stressors
Project leader: John Smol, Queen’s University

Summary: The paleolimnological project will collect sediment cores from the Network lakes and use biological remains preserved in the sediments to obtain information on how lakes across Canada have responded to human influences over the past ~200 years. We will identify changes through time by examining two groups of organisms with remains that preserve well in sediments: diatoms, a group of siliceous algae and chironomids, an insect family containing many taxa with aquatic larvae that are highly responsive to deepwater oxygen conditions. By comparing diatom and chironomid assemblages preserved in recent sediments with those deposited prior to widespread industrialization we will provide a broad assessment of how key water quality variables (e.g., pH, TP and bottom-water oxygen) have changed across the country. Furthermore, a subset of the lakes will be analyzed in greater detail (i.e. the full sediment core) to determine timing of any changes, rather than simply how the lakes differ from pre-impact conditions. VIRS inferred chlorophyll-a will also be analysed to provide an estimate of changes in lake primary productivity with time. Analyses of DNA, as well as cyanobacteria and cladocerans will also be performed, but these aspects of the project are described in projects 4 & 6.

Project 4: Linking genetic and microscopic approaches to reconstruct historical conditions of lake ecosystems
Project leader: David Walsh, Concordia University

Summary: In this project, we will develop and refine a paleogenetic approach for tracking lake health through time. Targeting the eukaryotic community, we aim to evaluate whether the similarity between subfossil and genetic analyses varies predictably as a function of environmental parameters (e.g., lake mixis, DOC or nutrient concentration). We will address the following questions: (1) How coherent are the results between classical taxonomic subfossil analyses and genetic techniques?; (2) Can we detect the presence of organisms through genetic analyses that do not leave a distinct morphological element?; (3) Is there significant genetic diversity within groups that leave a morphological fossil that would be otherwise undetected in the absence of a genetic analysis. The deliverables of this project are expected to include a greatly improved knowledge on the interpretation of genetic data in a paleolimnological context and the proposal of new DNA-based biological indicators for change in lakes.