Essential oils from Moroccan plants as promising ecofriendly tools to control toxic cyanobacteria blooms

The use of natural compounds obtained from many plant resources are considered the most promising and eco-friendly alternative approach for controlling harmful algae in aquatic ecosystems. In this study, the anti-cyanobacterial activity of essential oils (EOs) extracted from seven Moroccan aromatic and medicinal plants against unicellular Microcystis aeruginosa has been evaluated. The chemical composition of EOs was analyzed by GC-MS, and a total of 55 constituents were identified accounting for 97.6% to 100% of the total oils. The potential algicidal activity was evaluated qualitatively by the application of the paper disk diffusion method in solid medium and quantitatively by the application of broth microdilution methods in liquid medium. The results of solid medium showed that Chenopodium ambrosloides, Thymus broussonetia, Thymus maroccanus and Thymus satureioides essential oils inhibited totally the growth of Microcystis aeruginosa. while, Thymus Pallidus essential oil exhibited the weakest activity. The growth of the tested cyanobacteria was completely inhibited during the 5-days test period in liquid media by Thymus broussonetii, Thymus maroccanus and Thymus satureioides essential oils, while the lowest inhibition rates was observed with Thymus pallid= essential oil. Regarding the Minimum Inhibitory Concentration and Minimum Bactericidal Concentration values, it appears that Thymus broussonetii essential oil displayed the greatest potency, while the weakest effectiveness was achieved with Thymus paths essential oil. These findings provide a platform for the development of new ecofriendly and safer botanical materials, which may be used as effective alternative algicidal agents for controlling toxic cyanobacterial blooms.