Studies on phytoplankton and in particular Harmful Algal Blooms (HABs) species in southern Mediterranean waters are scarce. We performed from April 2008 to June 2009 weekly investigations on microphytoplankton community structure and abundance in two contrasted marine ecosystems located in the western Moroccan Mediterranean coast, M'diq Bay and Oued Laou Estuary. Simultaneously, we measured the main physico-chemical parameters. Globally, the two studied areas showed comparable values of the assessed abiotic environmental factors. Temperature and salinity followed seasonal variation with values ranging from 13.5 °C to 21.4 °C and 31 to 36.8, respectively. Average nutrient values in surface water ranged from 0.7 to 45.76 μM for dissolved inorganic nitrogen, 0.02–2.10 μM for PO₄ and 0.23–17.46 μM for SiO₄ in the study areas. A total of 92 taxa belonging to 8 taxonomic classes were found. The highest number of microphytoplankton abundance reached 1.2 × 10⁶ cells L⁻¹ with diatoms being the most abundant taxa. Factorial Discriminant Analysis (FDA) and Spearman correlation test showed a significant seasonal discrimination of dominant microphytoplankton species. These micro-organisms were associated with different environmental variables, in particular temperature and salinity. Numerous HABs species were encountered regularly along the year. Although Dinophysis species and Prorocentrum lima were present in both sites, no Lipophilic Shellfish Poisoning was detected for the analyzed bivalve mollusks. Domoic acid (DA), produced by toxic species of Pseudo-nitzschia was found with concentrations up to 18 µg DA g⁻¹ in the smooth clam Callista chione. Data showed that the observed persistent and dramatic Paralytic Shellfish Poisoning (PSP) intoxication of mollusks resulted probably of Gymnodinium catenatum proliferations in both studied areas. Contrary to C. chione, the cockle Achanthocardia tuberculatum showed a permanent and extremely high toxicity level during the 15 months survey with up to 7545 µg Equivalent Saxitoxin kg⁻¹ flesh (ten times higher than the sanitary threshold of 800 µg eqSTX Kg⁻¹flesh). The present work highlights for the first time the dynamic of microphytoplankton including HABs species and their associated toxin accumulation in the commercially exploited shellfish in the southern western Mediterranean waters of Morocco. Furthermore, the acquired data will help us to improve the monitoring of HABs species and related toxins in these coastal marine systems.

在地中海南部水域，对浮游植物，特别是有害藻华（HABs）种类的研究很少。我们从2008年4月至2009年6月对摩洛哥西部地中海沿岸M'diq湾和Oued Laou河口两个形成对比的海洋生态系统中的浮游植物群落结构和丰度进行了每周调查。同时，我们测量了主要的理化参数。在全球范围内，这两个研究领域显示出与评估的非生物环境因素相当的价值。温度和盐度随季节变化而变化，分别在13.5°C至21.4°C和31至36.8之间。地表水中的平均养分值对于溶解的无机氮为0.7至45.76μM，对于PO ₄为0.02–2.10μM，对于SiO为0.23–17.46μM₄在学习领域。总共发现了8个分类类别的92个分类单元。浮游植物的丰度最高，达到1.2×10 ⁶ 细胞L ^-1，其中硅藻是最丰富的分类单元。因子判别分析（FDA）和Spearman相关检验表明，主要的浮游植物种类有明显的季节性歧视。这些微生物与不同的环境变量有关，特别是温度和盐度。一年中经常遇到许多HABs物种。尽管恐龙生物和利马原中心在两个地点均存在，未检测到双壳贝类软体动物的亲脂性贝类中毒。在光滑的蛤Call Callista chione中发现了由假性尼兹菌属有毒物种产生的多摩酸（DA），其浓度高达18 µg DA g ^-1。数据显示，在两个研究区域观察到的对软体动物的持久性和剧烈麻痹性贝类中毒（PSP）中毒可能是由于裸子藻的繁殖所致。与C. chione相反，在15个月的调查中，鸟蛤无心动杆菌显示出永久且极高的毒性水平，当量毒死to毒素达7545 µg kg ^-1肉（比800 µg eqSTX Kg ^-1肉的卫生阈值高十倍）。本工作首次强调了摩洛哥南部地中海水域中商业开采的贝类中包括HABs种类在内的微浮游植物的动态及其相关毒素的积累。此外，获得的数据将帮助我们改善对这些沿海海洋系统中HAB物种和相关毒素的监测。