McGill University
M.Sc. candidate
Supervisor: Irene Gregory-Eaves
Lars Lonsmann Iversen
Start: 2023-09-01

Project

Uncovering historic macrophyte assemblage dynamics in southern Quebec lakes using sedimentary DNA
Macrophytes are pillars of aquatic ecosystems seeing as they provide habitat for a rich biodiversity of species and perform key ecosystem functions like dampening wave energy, promoting sedimentation, and enhancing biogeochemical cycling. Macrophyte community dynamics are strongly dependent upon the conditions of their aquatic habitats. Over the past 100 years, many lakes have been changing at an accelerated rate due to multiple stressors including eutrophication, water-¬level alterations, and climate change. Based on earlier paleolimnological work by Vermaire et al. (2012 CJFAS), we know that many lakes in southern Quebec have experienced macrophyte declines. The invasive Eurasian watermilfoil (Myriophyllum spicatum L.) has also been able to establish throughout the region. However, we do not know when and how macrophyte communities changed and have a poor understanding of the causes. The goals of this study are to use sedimentary DNA (sedDNA) to investigate how the southern Quebec macrophyte community has changed over the past ∼150 years, determine when Eurasian watermilfoil can first be detected in the region, and identify the strengths of possible drivers like nutrient inputs and land use changes. I hypothesize that macrophyte community diversity will decrease over time and that these declines will be associated with an increased presence of Eurasian watermilfoil, higher temperatures, and higher nutrient loads. The use of sedDNA will further our understanding of how macrophyte biodiversity has transformed over time and will indicate what factors influence changes in the community composition of North American lakes.

Keywords

Sedimentary DNA, Paleolimnology, Macrophytes, invasive species