RESEARCH ARTICLE Highlighting of the antialgal activity of organic extracts of Moroccan macrophytes: potential use in cyanobacteria blooms control Zakaria Tazart 1,2 & Mountasser Douma 1,3 & Ana Teresa Caldeira 2 & Lamiaa Tebaa 1 & Khadija Mouhri 1 & Mohammed Loudiki 1 Received: 27 May 2019 /Accepted: 13 March 2020 # Springer-Verlag GmbH Germany, part of Springer Nature 2020 Abstract Many studies have demonstrated the effectiveness of algicidal compounds produced by macrophytes against microalgae. The aim of this study was to assess the algicidal activity of seven Moroccan macrophyte ethyl acetate extracts (MEA) to control harmful algal blooms (HABs). The response and sensitivity of prokaryotic toxic cyanobacteria (Microcystis aeruginosa) and eukaryotic microalgae (Chlorella sp.) were highlighted. The algicidal effect of MEA extracts against the two microalgae was assessed using both the paper disc diffusion and microdilution methods. This last was used in order to evaluate the minimum inhibitory concentrations (MIC) and minimum algicidal concentrations (MAC). Results showed that the growth of both microalgae was significantly inhibited by all MEA extracts. Myriophyllum spicatum organic extract shows the highest growth inhibition activity against M. aeruginosa (35.33 ± 1.53) and Chlorella sp. (30.33 ± 1.15 mm). This stronger inhibitory activity was confirmed by the low MIC (6.25, 12.5 mg/L) and MAC (6.25, 12.5 mg/L) values. Furthermore, results showed different sensitivity between the prokaryotic and eukaryotic microalgae into MEA extracts. Based on the MIC and MAC values, we can distinguish two groups of plants. The first one, including M. spicatum, Ranunculus aquatilis, and Enteromorpha sp., can be considered as a preferable anti-prokaryotic group with a stronger inhibitory activity on M. aeruginosa growth. The second group, constituted by Potamogeton natans, Nasturtium officinale, Elodea sp., and Ceratophyllum sp., has a preferable and stronger inhibitory effect against eukaryotic algae (Chlorella sp.). Overall the results reveal the potential algicidal activity of macrophytes and suggested that MEA extracts could play an important role in biocontrol of HABs. Keywords Macrophytes . Algicidal activity . Sensitivity . Microcystis aeruginosa . Chlorella sp. . Biocontrol Introduction Harmful algal blooms (HABs) frequently occurred in eutro- phic waters (Paerl and Huisman 2009; Harke et al. 2016). They have a significant negative effects on aquatic organisms and present a serious risk to public health and aquatic envi- ronment worldwide (Carmichael and Boyer 2016). Therefore, the management of HABs is very important and urgent. The Responsible editor: Vitor Manuel Oliveira Vasconcelos * Mountasser Douma douma_mountasser@yahoo.fr Zakaria Tazart zakaria.tazart@gmail.com Ana Teresa Caldeira atc@uevora.pt Lamiaa Tebaa lamiaatebaa@gmail.com Khadija Mouhri mouhri@uca.ac.ma Mohammed Loudiki loudiki@uca.ac.ma 1 Water, Biodiversity and Climate Change Laboratory, Phycology, Biotechnology and Environmental Toxicology Research Unit, Faculty of Sciences Semlalia Marrakech, Cadi Ayyad University, Av. Prince My Abdellah P.O. Box 2390, 40000 Marrakech, Morocco 2 HERCULES Laboratory & Chemistry Department, School of Sciences and Technology, Évora University, Largo Marquês de Marialva 8, 7000-809 Évora, Portugal 3 Polydisciplinary Faculty of Khouribga (FPK), Sultan Moulay Slimane University, Beni Mellal, Morocco Environmental Science and Pollution Research https://doi.org/10.1007/s11356-020-08440-w