In a context of global change, the Aquitaine lake of Parentis-Biscarrosse (France) is subject to a double issue : on the one hand, the proliferation of two species of invasive aquatic macrophytes (E. densa and L. major) and, on the other hand, the upsurge of cyanobacteria blooms. Invasive macrophytes have a high growth rate and a very efficient vegetative reproduction. Recently, modern chemical approaches have shown that this reproductive success could be explained by the secretion of allelopathic compounds which affect the environmental communities. Moreover, studies have also shown that cyanobacteria would be the most sensitive algal group to this kind of interactions. The objective of this study is therefore to characterize by a non-targeted metabolomic approach, the effect of allelopathic compounds produced by E. densa and L. major on the toxigenic cyanobacteria M. aeruginosa. For this purpose, an experiment was carried out by putting in contact this strain of cyanobacteria and extracts of E. densa and L. major. The exposure took place in microcosms (glass balloons), during 96 hours and in a thermoregulated chamber. In a first step, measurements of chlorophyll concentration and photosynthetic yield were performed every day using a PhytoPAM. In a second step, the allelopathic relationships between our organisms were investigated through non-targeted metabolomic analyses. The results obtained indicate an inhibition of the photosynthetic yield of M. aeruginosa for macrophyte extract concentrations of 10g/L. The first results of the metabolomic analyses show a significant discrimination of our conditions, which suggests that there is a sensitivity of the M. aeruginosa metabolome to macrophyte extracts. Currently, the metabolomic analyses are still in progress.