| Title: |
Multiscale study of phytoplankton response to N:P imbalance in the Bay of Seine linking functional traits to community dynamics |
| Authors: |
Delatte, Lise; Massinot, Clara; Stoltz, Gaëlle; Hernández-Fariñas, Tania; Claquin, Pascal |
| Contributors: |
Marine Ecosystems and oRganisms reSEArch Lab (MERSEA); Université de Caen Normandie (UNICAEN); Normandie Université (NU)-Normandie Université (NU); Normandie Université (NU); Centre de recherches en environnement côtier (CREC); Laboratoire Environnement Ressources de Normandie (LERN); Unité Observation et écologie de la restauration des écosystèmes littoraux (COAST); Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER); Agence de l'Eau Seine Normandie; Région Normandie; ED 497 · NBISE · École doctorale Normande de biologie intégrative, santé, environnement; AGU; ASLO; The Oceanography society |
| Source: |
Ocean Sciences Meeting 2026 ; https://hal.science/hal-05556800 ; Ocean Sciences Meeting 2026, Feb 2026, Glasgow, United Kingdom |
| Publisher Information: |
CCSD |
| Publication Year: |
2026 |
| Collection: |
Normandie Université: HAL |
| Subject Terms: |
[SDE.BE]Environmental Sciences/Biodiversity and Ecology |
| Subject Geographic: |
Glasgow; United Kingdom |
| Description: |
International audience ; Development and growth of microalgae depend on 2 key macroelements: Nitrogen and Phosphorus. While single-nutrient limitation is well documented, attention on their relative availability also has to be considered. In marine systems, nutrient stoichiometry deviations can strongly affect physiology, community composition, and primary production. In the Bay of Seine, decades of nutrient inputs followed by improved wastewater treatment have led to N:P imbalance, linked to a Chlorophyll-a decline, which raises questions about how phytoplankton respond to nutrient imbalance under eutrophic and potentially co-limited conditions.This study explores impacts of N:P ratios, from cellular responses in local species to changes in natural community structure and ecophysiology. Semi-continuous cultures of phytoplankton and natural communities incubated in microcosms were grown under six N:P ratios representative of Bay of Seine conditions monthly during 2 years. Photosynthesis, biovolume, carbon excretion, and cell cycle were monitored as well as community composition (pico- to microphytoplankton), identified using flow cytometry and microscopy.Results show a decrease in growth with distance from N:P = 16, with a marked reduction in picophytoplankton at extreme ratios. Red fluorescing pico-nano and microphytoplankton (Picoeukaryotes, Nanoeukaryotes and Diatoms) consistently dominate while orange fluorescing groups (Synechococcales, Cryptophytes and Dinoflagellates) decline with increasing ratio, confirmed in monospecific cultures. Diatoms were less impacted by N:P variations with active photosynthesis and “growth” carbon allocation strategy, while flagellates showed physiological acclimation like cell enlargement, increasing light-harvesting complexes and switching to “storing” carbon strategy. By linking species-specific physiological acclimations to community responses, this work shows how phytoplankton can adjust to N:P variations and influence community structure and function. |
| Document Type: |
conference object; still image |
| Language: |
English |
| Availability: |
https://hal.science/hal-05556800; https://hal.science/hal-05556800v1/document; https://hal.science/hal-05556800v1/file/Delatte_et_al_Multiscale_study_OSM26_Poster.pdf |
| Rights: |
https://creativecommons.org/licenses/by-nc-nd/4.0/ ; info:eu-repo/semantics/OpenAccess |
| Accession Number: |
edsbas.D03C25F1 |
| Database: |
BASE |