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Paleolimnological reconstruction of trophic status of lakes Nairne (Charlevoix-Est) and Memphremagog (Estrie) Project

Quebec society is increasingly concerned about the consequences of the eutrophication of the lakes and cyanobacteria blooms. It is now crucial to achieve a deeper understanding of this problem, its origins, and its consequences, but also to increase our knowledge for taking concrete and appropriate action.

A paleolimnological approach will be used for this project. It will acquire the necessary data for the decision-making designed for the sound management of the lakes in the study.

The paleolimnological analysis of Lac Nairne (Charlevoix-East) and Lake Memphremagog (Eastern Townships) for the past 200 years will be conducted to reconstruct the recent history of these two water bodies. The three main bioindicators are: fossils diatoms; chlorophyll a pigments; and chironomidales capsules. The use of diatoms will target the key moments in the trophic evolution of the lakes. Analysis of chlorophyll a pigments will inform us about the development of biomass. Finally, the midges will serve as an indicator witness to corroborate the results obtained with the identification of diatoms.

The main objective of this project is to produce a paleolimnological diagnostic for each sediment core studied. The study was conducted in partnership with the private firm CIMA+. The report issued following the paleolimnological diagnosis will enable them to produce an appropriate action plan for each lake. This project is also integrated into a comprehensive study analyzing several lakes in southern Quebec to create reconstructive and predictive models. This study will be conducted by Ms. Roxane Tremblay, Ph.D. candidate at Laval University. Specifically, this study aims to:

– Distinguish the different past trophic stages for each of the lakes studied

– Identify natural and / or anthropogenic causes related to these trophic changes