Water, Biodiversity and Climate Change Laboratory, Faculty of Sciences Semlalia, Cadi Ayyad University, Av. Prince My Abdellah, P.O. Box 2390, Marrakech, 40000, Morocco; National Center for Studies and Research on Water and Energy, Cadi Ayyad University, P.O. Box: 511, 40000, Marrakech, Morocco; Department of Plankton and Microbial Ecology, Leibniz-Institute of Freshwater Ecology and Inland Fisheries (IGB), Zur alten Fischerhuette 2, 14775, Stechlin, Germany.
Natural Resources Engineering and Environmental Impacts Team, Multidisciplinary Research and Innovation Laboratory, Polydisciplinary Faculty of Khouribga, Sultan Moulay Slimane University of Beni Mellal, B.P.: 145, 25000, Khouribga, Morocco.
Harmful Algae. 2024 May;135:102631. doi: 10.1016/j.hal.2024.102631. Epub 2024 Apr 27.
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. In contrast, 4 km downstream of the reservoir, the concentration decreased by a factor of 5.39 to 29.63 µgL, 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 distribution. We emphasize the need for effective management strategies to minimize toxin transfer and ensure public health and safety.
蓝藻有害藻华（CyanoHABs）威胁着全球的公共健康和淡水生态系统。在本研究中，我们的主要目标是探索蓝藻水华的动态以及微囊藻毒素（MCs）如何从拉拉·塔克尔库斯特水库转移到附近的农场。我们使用 Landsat 图像、分子分析、收集和分析理化数据以及使用 HPLC 评估毒素。我们的调查确定了两种引发水华的蓝藻物种：微囊藻属和聚球藻属。我们的微囊藻株产生了三种 MC 变体（MC-RR、MC-YR 和 MC-LR），其中 MC-RR 在溶解态和细胞内毒素中表现出最高的浓度。相比之下，我们的聚球藻株没有产生任何可检测到的毒素。为了验证我们的归一化植被指数（NDVI）结果，我们利用湖沼学数据，包括藻类细胞计数，并定量了从水库中采集的微囊藻水华样品中的 MCs。我们的研究揭示了 30 年来水库中蓝藻增殖的模式和趋势，并使用 NDVI 方法提供了该地区蓝藻浸染的历史地图。研究发现，由于微囊藻的浮力，MC-LR 积聚在水面附近。水库水中 MC-LR 的最大浓度为 160 µg L。相比之下，在水库下游 4 公里处，浓度降低了 5.39 到 29.63 µgL，表明随着与水华源距离的增加，MC-LR 浓度降低。同样，同一距离处 MC-YR 浓度降低了 2.98 倍。有趣的是，MC 分布随深度而变化，MC-LR 在水面占主导地位，而 MC-YR 在 10 米水深的水库出口处占主导地位。我们的研究结果强调了营养物浓度、环境因素和转移过程对水华动态和 MC 分布的影响。我们强调需要采取有效的管理策略来最小化毒素转移，确保公共健康和安全。
