TRACING THE TROPHIC HISTORY OF TEMPERATE LAKE MASKINONGÉ (MONT-TREMBLANT, CANADA): INSIGHTS FROM A MULTI-PROXY PALEOLIMNOLOGICAL APPROACH

Freshwater ecosystems worldwide are increasingly impacted by human activities. Lakes with diverse human activities in their catchments are particularly vulnerable to nutrient overload and other pollutants, resulting in water quality deterioration and ecological shifts. Environmental authorities often face the challenge of a paucity of long-term data, hampering their ability to contextualize recent environmental changes against historical natural variability. Here, we use a multi-proxy paleolimnological approach, combined with historical document research, to trace the responses of temperate Lake Maskinongé (Mont-Tremblant, Canada) to stressors such as lumbering, agriculture, suburbanization and dam construction. Our main objective is to retrace the lake’s trophic history from the 16^th century to the present to establish reference conditions. Various biogeochemical analyses were carried out on two sediment cores retrieved in 2023, including microbiological analyses (diatom assemblages), scans (CT, ITRAX, hyperspectral) and sedimentological analyses (LOI, grain size). ²¹⁰Pb dating provided a temporal framework, and an inference model based on diatom assemblages, developed by Tremblay et al. (2014), generated past TP concentrations. Our results reveal a significant increase in eutrophic diatom species, chlorophyll a, organic matter and grain size in the last 50 years, highlighting the need for targeted restoration. Insights gained from this project contribute to essential knowledge for managing temperate lakes facing similar eutrophication challenges.

Presentation Preference: Oral

Primary Presenter: Louis-Marc Bruneau-Dumoulin, University Laval (louis-marc.bruneau-dumoulin.1@ulaval.ca)

Authors:

Louis-Marc Bruneau-Dumoulin, University Laval, Department of geography  (louis-marc.bruneau-dumoulin.1@ulaval.ca)

Raoul-Marie Couture, University Laval, Department of chemistry  (raoul.couture@chm.ulaval.ca)

Hamid Ghanbari, University Laval, Department of geography  (hamid.ghanbari.1@ulaval.ca)

Émilie Saulnier-Talbot, University Laval, Department of geography and Department of biology  (emilie.saulnier.talbot@bio.laval.ca)