Supervised by:

Pascal Bernatchez (Regular Member (Co-researcher))

Co-supervised by:

Michelle Garneau (Associate Member)

Research project description

Ecogeomorphologic Response of the Magdalen Islands Salt Marshes to Recent Sea Level Rise

Introduction

Sea level rise represents one of the most significant consequences of global climate change. The Magdalen Islands, an archipelago located in the center of the Gulf of St. Lawrence, experience relative sea-level rise rates that exceed the global average. This poses a significant environmental challenge and threatens a population of over 12,000 inhabitants and coastal infrastructure. Furthermore, the islands experience a particularly strong winter storm regime due to prevailing winds in the region's climate. Coastal marshes of the Magdalen Islands, unlike continental marshes, have low sediment accumulation rates, mainly due to the absence of terrigenous sediment input from rivers. Therefore, the region provides an excellent environment to assess the expected effects of sea-level rise on coastal ecosystems.

Objectives

The main objective of the project is to document the ecogeomorphologic responses of the coastal marshes of the Magdalen Islands to the relative sea-level rise over the past centuries. The specific objectives are as follows: 1.Reconstruct paleoenvironments. 2.Inventory ecological and geomorphological indicators of the effects of sea-level rise and storms on the marshes. 3.Map the spatio-temporal trajectories of the marshes and transitional coastal ecosystems (bog, shrub and coniferous forest).

Study Sites

The documentation of the ecogeomorphologic response of the coastal marshes and transitional ecosystems of the Magdalen Islands is conducted through three study sites, which are as follows: 1. The 'Bassin aux Huîtres' marsh, located on Grande-Entrée Island in the lagoon of the same name. 2. The 'Bassin' marsh, located on Havre Aubert Island in the Le Bassin lagoon. 3. The 'Sillons' marsh, located on Havre aux Maisons Island in the Grande Entrée lagoon. These sites represent the coastal marshes found on the islands, which include organic marshes nestled in lagoons that encompass a range of ecosystems typical of the archipelago, such as coastal marsh, shrub and/or bog, and coniferous forest. The chosen marshes exhibit multiple signs of marine submersion and resulting coastal adjustments, such as erosion of the lower marsh and the decline of the bordering forest due to the intrusion of marine water and rising groundwater.

Material and methods

Two techniques will be used to document how coastal marshes respond to rising sea levels: (1) analyzing sediment cores to reconstruct historical environmental conditions and (2) mapping the coastline from the 1960s to the present to assess recent changes due to sea level rise. Ecological and sedimentological indicators will be analyzed on sediment cores collected from the three marshes in the summer of 2022 to reconstruct the coastal paleoenvironment over the past few centuries. Fieldwork has also been conducted to identify the effects of sea-level rise and storms on the marshes. By integrating both spatiotemporal techniques, a better understanding of the ecogeomorphologic response of coastal marshes to sea-level rise is aimed.

Expected results

Meeting these objectives will help create a comprehensive overview of the ecogeomorphologic adaptations of coastal marshes and transitional ecosystems in the current scenario of rising sea levels. This depiction will serve as an early indicator of the changes that may be expected on coastlines elsewhere in the world.

Research Site Coordinates