Supervised by:

Pascal Bernatchez (Regular Member (Co-researcher))

Co-supervised by:

Michelle Garneau (Associate Member)

Research project description

Ecomorphological evolution of the Kamouraska and L'Isle-Verte salt marshes since the Late Holocene: implications for ecological services

Introduction

Salt marshes are recognized for providing numerous ecosystem services, including being important reservoirs of biodiversity, offering natural coastal protection against erosion, and possessing a high potential for carbon sequestration. In view of the threat posed by rising sea levels, it is vital to gain a better understanding of the impact of these environments. This project will attempt to answer the following question: what is the ecogeomorphological response of salt marshes with seasonal ice cover to rising sea levels? It will be based on the hypothesis that rising sea levels will lead to a reduction in the relative surface area of upper schorre at the expense of lower schorre, resulting in a loss of plant diversity and ecological services.

Objectives

This study will focus on characterizing the present and past evolution of the upper schorre in relation to that of the lower schorre (objective 1). An analysis of the inter-annual surface variation of these two zones will be carried out (objective 1.1). The transition periods between upper and lower schorre will then be studied and dated (objective 1.2). Finally, sedimentation rates as a function of sea-level rise will also be calculated (objective 1.3). The second objective will attempt to assess the impact of sea-level rise on ecological services (objective 2). A description and evolution of current and past plant communities will be carried out (objective 2.1) and the rate of carbon sequestration by the environment will be calculated (objective 2.2).

Study Sites

This project will take place in two salt marshes located in the Lower St. Lawrence region, on the middle estuary of the St. Lawrence River, and subject to a seasonal ice regime (December to April). The first is located in Saint-Germain-de-Kamouraska (MRC de Kamouraska) and the second in the municipality of L'Isle-Verte (MRC de Rivière-du-Loup).

Material and methods

The first objective will employ various remote sensing methods (satellite image archives, high-resolution drone imagery and cartographic classification methods). Transition periods will be described using sediment cores collected at the sites and foraminiferal counts. Dates associated with transition periods will be obtained by lead-210 and carbon-14 analysis. The second objective will use remote sensing tools similar to the first, and will be coupled with vegetation inventories carried out at the study sites. The evolution of older vegetation communities will be assessed using macrofossils counts from core samples. Finally, carbon sequestration rates will be determined through loss-on-fire and elemental carbon-hydrogen-nitrogen (CHN) analyses, also performed on sediment cores.

Expected results

The results of this study should highlight the ecological importance of salt marshes under seasonal ice cover and at latitudes such as those of the Estuary and Gulf of St. Lawrence. They will also provide a better understanding of the highly variable ecogeomorphological evolution of these coastal environments, particularly in relation to accelerating sea-level rise.

Research Site Coordinates