Chemical landscape of invasive aquatic plant exometabolomes
Résumé
Egeria densa and Lagarosiphon major are the main invasive hydrophytes in French Atlantic Lakes. These exotic species can modify trophic levels by producing large quantities of biomass in lakes, and have been studied and monitored for many years. Previous investigations revealed the occurrence of endogenous metabolites in these plants known to be able to influence epiphytic communities, phytoplankton, or other plants. Nevertheless, the actual excretion and environmental occurrence of these metabolites remain poorly documented. Thus, there is a need to gain knowledge of the actual occurrence and potential ecological impact of E. densa and L. major exometabolome, especially through their allelopathic potential. To this end, untargeted metabolomics using high-resolution mass spectrometer and chemometrics approaches is relevant through its ability to depict, as a first step, the exometabolome chemical landscape. In this context, this study aims to investigate, in these invasive plants, the excretion kinetic of biomolecules, especially those known for their allelopathic properties. To do so, plants and surrounding water were collected on Lacanau lake. After a period of acclimatization, photosynthetically active plant fragments of both species were grown separately under controlled conditions in inner mesocosms of 10 L of sterilized water for 10 days. Plant fragments were cultured under two different light conditions: 1) in the dark simulating the absence of irradiance of the lower part of plant stands, near the sediment; 2) nycthemeral cycle based on the seasonal photoperiod. Nutrients, temperature and density conditions were similar to those occurring within the field. Metabolomics was implemented on samples collected after 1, 2, 5 and 8 days and on plant surrounding waters from the lake. PCA and HCA showed significant discrepancies in exometabolome between the two species both in the field and in the mesocosms. ASCA analysis highlighted the significant effect of the time and the species and their interaction in the exometabolome fingerprint while the light regime did not have any effect. Further investigations are ongoing to characterize the endo- and the surface metabolome of both invasive species to unravel their actual contribution to the exometabolome chemical landscape, especially on the field.
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