The Benguela upwelling system, considered the world’s most productive marine ecosystem, has a long record of potentially toxic diatoms belonging to the genus Pseudo-nitzschia. Species of Pseudo-nitzschia were reported as early as 1936 from the northern Benguela upwelling system (nBUS). For the current study, long-term phytoplankton monitoring data (2004–2011) for the Namibian coast were analysed to examine inshore and offshore temporal distribution of Pseudo-nitzschia species, their diversity and ultrastructure. The potentially toxigenic P. pungens and P. australis were the dominant inshore species, whereas offshore Pseudo-nitzschia showed a higher diversity that also included potentially toxic species. During a warming event, a community shift from P. pungens and P. australis dominance to P. fraudulenta and P. multiseries was documented in the central nBUS.

A case study of a toxic event (August 2004) revealed that P. australis and P. pungens were present at multiple inshore and offshore stations, coincident with fish (pilchard) and bird mortalities reported from the central part of Namibia. Toxin analyses (LC–MS/MS) of samples collected from June to August 2004 revealed the presence of particulate domoic acid (DA) in seawater at multiple stations (maximum ∼180 ng DA/L) in the >0.45 μm size-fraction, as well as detectable DA (0.12 μg DA/g) in the gut of one of two pilchard samples tested. These findings indicate that DA may have been associated with the fish and bird mortalities reported from this event in the nBUS. However, the co-occurrence of very high biomass phytoplankton blooms suggests that other explanations may be possible.

Benguela上升流系统被认为是世界上生产力最高的海洋生态系统，长期以来存在着属于伪拟南芥属的潜在有毒硅藻记录。早在1936年，本格拉北部上升流系统（nBUS）就报道了假性尼兹菌种。在本研究中，对纳米比亚海岸的长期浮游植物监测数据（2004-2011年）进行了分析，以检查拟南芥属物种的近岸和近海时间分布，它们的多样性和超微结构。具有潜在毒性的P. pungens和P. australis是主要的近岸物种，而近海的拟南芥表现出更高的多样性，其中还包括潜在的有毒物种。在变暖事件中，在中央nBUS中记录了一个社区，从庞氏假单胞菌和澳大利亚假单胞菌的优势转移到欺诈性假单胞菌和多系列假单胞菌。

一种有毒的事件（2004年8月）的案例研究表明，芦苇和P. pungens目前在多个近岸和近海站，鱼（沙丁鱼）和鸟类死亡重合来自纳米比亚的中心部分的报道。对2004年6月至2004年8月收集的样品进行的毒素分析（LC-MS / MS）表明，在大于0.45μm大小的馏分中，多个站位的海水中都存在颗粒状海藻酸（DA）（最大约180 ng DA / L），以及两个被测试的沙丁鱼样品之一的肠道中可检测到的DA（0.12μgDA / g）。这些发现表明，DA可能与nBUS中此事件报告的鱼和鸟死亡有关。然而，很高生物量浮游植物水华的同时出现表明其他解释可能是可能的。