Ines ZRIBI

Study on the Impact of Nitrogen/Phosphorus (N/P) Imbalance on Phytoplankton Growth in a Photobioreactor

The Seine Bay faces eutrophication and dystrophy issues, with an imbalanced nitrogen/phosphorus (N/P) ratio due to reduced phosphorus inputs and persistently high nitrogen levels, despite improvements in wastewater treatment. Nutrient inputs and their stoichiometry play a key role in phytoplankton growth, community structure, and the consequences of phytoplankton blooms. This project aims to analyze the impact of N/P ratios on the growth of certain phytoplankton species under controlled conditions. Selected species (e.g., diatoms like Skeletonema marinoi) will be cultured in cylindrical photobioreactors (Synoxis Algae) in both batch and continuous modes. Carbon (C) input will also be examined. Parameters such as photosynthetic efficiency, nutrient uptake kinetics (Ks and Vmax), cell size variations, and the expression of stress markers like carbon excretions (TEP, EPS) will be measured.