Supervised by:

Milla Rautio (Regular Member (Co-researcher))

Research project description

Cycling of the organic matter in Arctic and boreal lakes

Introduction

Arctic, subarctic and boreal regions contain the absolute majority of the world's lakes, yet these areas are among the least accessible, and thus, the least studied environments of our planet. Despite the already recognised status for northern lakes as sentinels of environmental change, as well as important hot spots for microbial activity of otherwise severe Nordic conditions, there are still a lot of gaps in our understanding of the organic matter cycling in these aquatic ecosystems - especially when it comes to the winter season, which dominates the regions in question. Knowing more about the quality of organic matter accumulated in lakes from different ecological regions, and more about microbial activity under ice in winter, would substantially help us to better understand the present effect of these lakes on global carbon cycle, and better predict the potential future outcomes under the global climate change.

Objectives

My main research interest is the relationship between the lake and its terrestrial environment, with more specific focuses on how the latter can affect the organic matter content in the lake (including its sediments), its cycling by lake’s microbiota, and eventually the greenhouse gas production and emissions. This interest is presently expressed with 3 projects: 1) a study of greenhouse gas production and sediment organic matter quality in lakes along a south-north gradient (in Western Canada, from the prairies to the tundra), 2) a study of qualities of organic matter in forest soils surrounding lakes with varying altitude, in the Saguenay region, and 3) a study of winter organic matter cycling and the fate of greenhouse gases under ice in a boreal lake; pathways and timing of greenhouse gas production, consumption, accumulation, and evasion from a lake in winter are very little studied so far.

Study Sites

My study sites are located across Canada, including Nunavut, Saskatchewan and Quebec. For the project 1, I study 19 lakes in Saskatchewan (across all the province from the prairies into the boreal forests), and 4 lakes in Victoria Island, Nunavut (representing tundra). Although these lakes are in a wide range of terrestrial environments and climate, both strongly affecting the quantity and quality of terrestrial organic matter, they are all located in a similar geological setting – that being, flatlands underlain by sedimentary rocks and glaciogenic Quaternary sediments. For the other projects (2 and 3), all the boreal lakes are in the Saguenay region, Quebec. They are in a mountainous area, underlain by crystalline rocks of Canadian shield, but vary in altitude, resulting in their environment ranging from mixed forests to upland taiga-like coniferous forests and wetlands.

Material and methods

I use a wide range of methods, starting from those needed to characterise the lake’s water column and ice, to sediment coring and sampling of surrounding forest soils. Spectral characterisation of dissolved organic matter is an important part of my project, as well as the characterisation of fatty acids (of particulate matter in water column, sediments, and soils). These two approaches help me to study the quality of organic matter accumulated in lake sediments, and available in the water column. The most important axis of the project, however, is the estimation of the size of the dissolved greenhouse gas pool (including CO2, CH4, and N2O) in the studied lakes. For project 1, I would conduct an incubation experiment to measure CO2 and CH4 production in lake sediments, to better understand the quality of accumulated organic matter in lakes from different ecoregions.

Expected results

For the project 1, I expect the southern lakes to be more productive, both in primary production and respiration of greenhouse gases; however, it remains to be seen whether lakes are more affected by the type of environment (e.g., forest versus grasslands) or other conditions (e.g., temperature, stratification). Overall, I would predict, that with global warming, the spreading of forests northwards would lead to increased productivity of tundra lakes. For #2, I expect lakes in higher altitudes to receive significantly different (and of lower quality for lake microbiota) terrestrial organic matter than those surrounded by mixed forests, in lower altitudes.

Research Site Coordinates

Scientific Communications

Ayala, P., Bogard, M.J., Grosbois, G., Preskienis, V., Culp, J.M., Power, M., Rautio, M., 2024. Dominance of net autotrophy in arid landscape low relief polar lakes, Nunavut, Canada. Global Change Biology, 30(e17193): 1-19. DOI: 10.1111/gcb.17193.

Preskienis, V., Laurion, I., Bouchard, F., Douglas, P., Billett, M., Fortier, D., Xu, X., 2021. Seasonal patterns in greenhouse gas emissions from lakes and ponds in a High Arctic polygonal landscape. Limnology and Oceanography, 66(S1: Biogeochemistry and ecology across Arctic aquatic ecosystems in the face of change): S117-S141. DOI: 10.1002/lno.11660.