Monitoring of toxic cyanobacterial blooms in Lalla Takerkoust reservoir by satellite imagery and microcystin transfer to surrounding farms

• Published in: Harmful algae 2024-05, Vol.135, p.102631, Article 102631
• Main Authors: Mugani, Richard, El Khalloufi, Fatima, Kasada, Minoru, Redouane, El Mahdi, Haida, Mohammed, Aba, Roseline Prisca, Essadki, Yasser, Zerrifi, Soukaina El Amrani, Herter, Sven-Oliver, Hejjaj, Abdessamad, Aziz, Faissal, Ouazzani, Naaila, Azevedo, Joana, Campos, Alexandre, Putschew, Anke, Grossart, Hans-Peter, Mandi, Laila, Vasconcelos, Vitor, Oudra, Brahim
• Format: Article
• Language: English
• Subjects: Cyanobacteria - growth & development; Cyanobacteria - physiology; Environmental Monitoring - methods; Harmful Algal Bloom; Indonesia; Lakes - microbiology; Landsat imagery; Microcystins - analysis; Microcystins - metabolism; Microcystis; Microcystis - growth & development; Microcystis - physiology; Molecular analysis; NDVI; Satellite Imagery; Synechococcus; Synechococcus - physiology; Toxin transfer
• ISSN: 1568-9883; 1878-1470; 1878-1470
• DOI: 10.1016/j.hal.2024.102631

•MCs in isolate are approximately 7 times lower than natural blooms from which it was isolated.•Investigating cyanobacterial dynamics and microcystin transfer from reservoirs to farms.•Identification of key cyanobacteria species: Microcystis (toxin producer) and Synechoccus (non-toxic).•Conducting a comprehensive investigation employing Landsat imagery, molecular analysis, and HPLC/LM/MS toxin assessment.•Gaining insights from NDVI analysis: revealing 30-year cyanobacterial proliferation patterns, depth variations, and distance-driven toxin dynamics. Cyanobacterial harmful algal blooms (CyanoHABs) threaten public health and freshwater ecosystems worldwide. In this study, our main goal was to explore the dynamics of cyanobacterial blooms and how microcystins (MCs) move from the Lalla Takerkoust reservoir to the nearby farms. We used Landsat imagery, molecular analysis, collecting and analyzing physicochemical data, and assessing toxins using HPLC. Our investigation identified two cyanobacterial species responsible for the blooms: Microcystis sp. and Synechococcus sp. Our Microcystis strain produced three MC variants (MC-RR, MC-YR, and MC-LR), with MC-RR exhibiting the highest concentrations in dissolved and intracellular toxins. In contrast, our Synechococcus strain did not produce any detectable toxins. To validate our Normalized Difference Vegetation Index (NDVI) results, we utilized limnological data, including algal cell counts, and quantified MCs in freeze-dried Microcystis bloom samples collected from the reservoir. Our study revealed patterns and trends in cyanobacterial proliferation in the reservoir over 30 years and presented a historical map of the area of cyanobacterial infestation using the NDVI method. The study found that MC-LR accumulates near the water surface due to the buoyancy of Microcystis. The maximum concentration of MC-LR in the reservoir water was 160 µg L−1. In contrast, 4 km downstream of the reservoir, the concentration decreased by a factor of 5.39 to 29.63 µgL−1, indicating a decrease in MC-LR concentration with increasing distance from the bloom source. Similarly, the MC-YR concentration decreased by a factor of 2.98 for the same distance. Interestingly, the MC distribution varied with depth, with MC-LR dominating at the water surface and MC-YR at the reservoir outlet at a water depth of 10 m. Our findings highlight the impact of nutrient concentrations, environmental factors, and transfer processes on bloom dynamics and MC d