My name is Marie and I’m a PhD student in limnology at Laval University, Quebec Canada. My project is understanding the effects of global climate change and anthropogenic activities on northern ecosystems using limnologic evidence.

 

Since my beginnings in geographical sciences, understanding the functioning of ecosystems and their temporal evolution has always fascinated me. It is therefore logical that I wanted to enter the world of limnology for my end-of-master’s project, in creating a diatom flora for the Tursujuq National Park biomonitoring project. After a year of photography, hundreds of taxa identified, and others difficult to identify in the context of a pandemic, I found myself under the spell of these ornamented fossils. It is for me the beginning of a long journey through this complex science.

For the first part of my graduate project, the study area is Tursujuq National Park, the largest park in Québec (~26,500 km2), located in the Hudson Bay region of Nunavik (northern Québec) (Figure. 1). As a protected area, the park will be an important reference site during the development of the North. Despite the need for baseline data to assist in the protection of this vast area, there is a lack of studies on its aquatic ecosystems. This project aims to conduct the first comprehensive, integrated assessment of the past, present and future of the aquatic ecosystems of Tursujuq National Park. We are developing proxy records, based on diatom analyses, that will assess the effects of past climate change and human activities, which will help our understanding about how northern ecosystems may respond in the future to human impacts and changes in climate. This research will generate information that will be essential for the successful future management of this special northern protected area. The project has three specific objectives: 1. Determining the baseline limnological conditions in lakes across Tursujuq National Park; 2. Developing bioindicators for monitoring future environmental change; and 3. Reconstructing past climate variability in the Hudson Bay region through analysis of sediment cores.

To reach these objectives we sampled 49 lakes in two stages. In the summer of 2015, 35 lakes were sampled in the Lake Wiyâshâkimi and Umiujaq sectors, while in the summer of 2016 a second series of 14 lakes was sampled between the first two sectors (Figure 1). Surface sediment samples were taken from each lake with a “Mini-Glew” corer (Glew, 1991), and subsurface water samples were taken for detailed water chemistry analysis. Four long sediment cores were also taken in strategic lakes (2 near to human settlements and 2 in remote wilderness sites). In the laboratory, cover slips with diatoms solutions were mounted on microscope slides. Light microscope observations permitted counting and identification of 500 valves per lake (Figure 2). Carbon14 samples for dating were taken from the long cores at inflection points in the diatom and sedimentology profiles. An Itrax scan documenting was done on the longer core (100 cm). This permit to recorded chemical profiles along sediment samples for a broad range of elements.

Preliminary results show that this area has a great diversity of diatoms, with more than 500 taxa (species and varieties) identified in 78 different genera. The most common genera in the 48 lakes (i.e. present in at least 45 lakes) were: Achnanthidium, Brachysira, Encyonema, Eunotia, Frustulia, Gomphonema, Neidium, Nitzschia, Pinnularia, Psammothidium, Stauroneis and Tabellaria. Detailed taxonomic studies are currently being carried out, especially on small naviculoid and achnanthoid species, to advance our knowledge on the autecology of these taxa using fine-grained identifications

Preliminary ecological analyses have indicated that specific conductivity is the main determining factor controlling diatom species relative abundances. Indeed, multivariate statistical analyses show that sodium (Na) and Magnesium (Mg) concentrations have a high effect, with a longitudinal decrease in concentrations (Figure 3).

This is largely due to the proximity to the marine influence of Hudson Bay, and the dominance of surface deposits of marine origin with high ionic content, in the western sector of the park. Nitrogen also influences assemblage distributions, but without a similar longitudinal geographical pattern. We are not sure about the origin or cycling of the nitrogen. The development of transfer functions will make it possible to analyze community changes from long sediment cores and reconstruct past climate variability.

This work is fascinating, due to its diversity of analyses in the laboratory and in microscopy. New species are being discovered and new assemblages will ultimately, I hope, allow a better understanding of the complex dynamics between these proxies and their environment.