EXPLORING THE INTERPLAY BETWEEN NUTRIENT AND LIGHT AVAILABILITY ON EELGRASS PHYSIOLOGY

Cumulative human activities are increasing nutrient inputs in coastal zones, driving eutrophication, and harming key ecosystems like eelgrass meadows. In excess, nitrogen promotes faster-growing primary producers that can outcompete eelgrass for nutrients and light. However, the combined effects of these two factors on eelgrass health—especially across a broad range of environmental conditions—are still overlooked. To address this gap, we conducted a laboratory experiment to assess the single and combined effects of nutrient and light availability on the widely distributed eelgrass (Zostera marina L.). In August 2024, eelgrass cores were collected from Rimouski Bay (QC, Canada) and placed in a nearby open-flow system. Following a one-week acclimation, the cores were randomly exposed to 2 nutrient levels (ambient and enriched) and 8 light intensities (ranging from 6 to 965 μmol photons m^-2 s^-1),  with 3 replicates per crossed condition. Eelgrass photosynthetic traits, including F_v/F_m and Rapid Light Curves, were monitored using non-invasive PAM fluorometry. After a two-week exposure, leaf chlorophyll a concentration was measured on 9 shoots per crossed condition. Preliminary results reveal that eelgrass shoots can be grouped based on their response to light availability. Moreover, nutrient enrichment seems to enhance their photosynthetic capacity. By combining gradient-based and multi-stressor approaches, this study will provide insights into potential thresholds in eelgrass responses to nutrient and light stress.

Presentation Preference: Poster

Primary Presenter: Lauriane Belles-Isles, Université du Québec à Rimouski (laurianebellesisles@gmail.com)

Authors:

Lauriane Belles-Isles, Université du Québec à Rimouski/ Institut des sciences de la mer de Rimouski/ Québec-Océan  (lauriane.belles-isles@uqar.ca)

Fanny Noisette, Université du Québec à Rimouski/ Institut des sciences de la mer de Rimouski/ Québec-Océan  (fanny_noisette@uqar.ca)

Caroline Fink-Mercier, Université du Québec à Rimouski/ Institut des sciences de la mer de Rimouski/ Québec-Océan  (caroline_fink-mercier@uqar.ca)

Brigitte Légaré, Université du Québec à Rimouski/ Département de Biologie, Chimie et Géographie/ Québec-Océan  (brigitte.legare@uqar.ca)

Ludovic Pascal, Université du Québec à Rimouski/ Institut des sciences de la mer de Rimouski/ Québec-Océan  (ludovic_pascal@uqar.ca)

Philippe Archambault, Université Laval/ Takuvik/ Québec-Océan  (philippe.archambault@bio.ulaval.ca)

Chrisitan Nozais, Université du Québec à Rimouski/ Département de Biologie, Chimie et Géographie/ Québec-Océan  (christian_nozais@uqar.ca)