Harmful algal blooms (HAB) are recurrent phenomena in northern Europe along the coasts of the Baltic Sea, Kattegat-Skagerrak, eastern North Sea, Norwegian Sea and the Barents Sea. These HABs have caused occasional massive losses for the aquaculture industry and have chronically affected socioeconomic interests in several ways. This status review gives an overview of historical HAB events and summarises reports to the Harmful Algae Event Database from 1986 to the end of year 2019 and observations made in long term monitoring programmes of potentially harmful phytoplankton and of phycotoxins in bivalve shellfish. Major HAB taxa causing fish mortalities in the region include blooms of the prymnesiophyte Chrysochromulina leadbeateri in northern Norway in 1991 and 2019, resulting in huge economic losses for fish farmers. A bloom of the prymesiophyte Prymnesium polylepis (syn. Chrysochromulina polylepis) in the Kattegat-Skagerrak in 1988 was ecosystem disruptive. Blooms of the prymnesiophyte Phaeocystis spp. have caused accumulations of foam on beaches in the southwestern North Sea and Wadden Sea coasts and shellfish mortality has been linked to their occurrence. Mortality of shellfish linked to HAB events has been observed in estuarine waters associated with influx of water from the southern North Sea. The first bloom of the dictyochophyte genus Pseudochattonella was observed in 1998, and since then such blooms have been observed in high cell densities in spring causing fish mortalities some years. Dinoflagellates, primarily Dinophysis spp., intermittently yield concentrations of Diarrhetic Shellfish Toxins (DST) in blue mussels, Mytilus edulis, above regulatory limits along the coasts of Norway, Denmark and the Swedish west coast. On average, DST levels in shellfish have decreased along the Swedish and Norwegian Skagerrak coasts since approximately 2006, coinciding with a decrease in the cell abundance of D. acuta. Among dinoflagellates, Alexandrium species are the major source of Paralytic Shellfish Toxins (PST) in the region. PST concentrations above regulatory levels were rare in the Skagerrak-Kattegat during the three decadal review period, but frequent and often abundant findings of Alexandrium resting cysts in surface sediments indicate a high potential risk for blooms. PST levels often above regulatory limits along the west coast of Norway are associated with A. catenella (ribotype Group 1) as the main toxin producer. Other Alexandrium species, such as A. ostenfeldii and A. minutum, are capable of producing PST among some populations but are usually not associated with PSP events in the region. The cell abundance of A. pseudogonyaulax, a producer of the ichthyotoxin goniodomin (GD), has increased in the Skagerrak-Kattegat since 2010, and may constitute an emerging threat. The dinoflagellate Azadinium spp. have been unequivocally linked to the presence of azaspiracid toxins (AZT) responsible for Azaspiracid Shellfish Poisoning (AZP) in northern Europe. These toxins were detected in bivalve shellfish at concentrations above regulatory limits for the first time in Norway in blue mussels in 2005 and in Sweden in blue mussels and oysters (Ostrea edulis and Crassostrea gigas) in 2018. Certain members of the diatom genus Pseudo-nitzschia produce the neurotoxin domoic acid and analogs known as Amnesic Shellfish Toxins (AST). Blooms of Pseudo-nitzschia were common in the North Sea and the Skagerrak-Kattegat, but levels of AST in bivalve shellfish were rarely above regulatory limits during the review period. Summer cyanobacteria blooms in the Baltic Sea are a concern mainly for tourism by causing massive fouling of bathing water and beaches. Some of the cyanobacteria produce toxins, e.g. Nodularia spumigena producer of nodularin, which may be a human health problem and cause occasional dog mortalities. Coastal and shelf sea regions in northern Europe provide a key supply of seafood, socioeconomic well-being and ecosystem services. Increasing anthropogenic influence and climate change create environmental stressors causing shifts in the biogeography and intensity of HABs. Continued monitoring of HAB and phycotoxins and the operation of historical databases such as HAEDAT provide not only an ongoing status report but also provide a way to interpretate causes and mechanisms of HABs

有害藻华（HAB）是北欧沿波罗的海，卡特加特-斯卡格拉克，北海东部，挪威海和巴伦支海沿岸的常见现象。这些有害生物危害品偶尔给水产养殖业造成巨大损失，并以多种方式长期影响着社会经济利益。本状态审查概述了HAB的历史事件，并总结了从1986年到2019年底的有害藻类事件数据库的报告以及对双壳贝类中潜在有害浮游植物和藻毒素的长期监测计划的观察结果。导致该地区鱼类死亡的主要HAB类群包括褐藻类植物Chrysochromulina Leadbeateri的花朵1991年和2019年在挪威北部发生的情况，给养鱼户造成了巨大的经济损失。1988年在Kattegat-Skagerrak上生长的旱生多菌Prymnesium polylepis（同名Chrysochromulina polylepis）对生态系统造成了破坏。在prymnesiophyte的赤潮棕囊藻属。在北海西南部和瓦登海沿岸的海滩上造成泡沫堆积，贝类死亡率与其发生有关。在与北海南部水流入有关的河口水域中，已观察到与HAB事件有关的贝类的死亡率。鳞生植物属假单胞菌属的第一朵花在1998年观测到这种现象，从那以后，在春季高密度的细胞中观察到了这种花开，几年后导致了鱼的死亡。鞭毛虫，主要是Dinophysis spp。，间歇性地产生蓝贻贝，Mytilus edulis中的腹泻性贝类毒素（DST）浓度，超过挪威，丹麦和瑞典西海岸的监管限值。平均而言，自2006年左右以来，瑞典和挪威Skagerrak海岸的贝类中DST含量有所下降，这与D. acuta的细胞丰度下降相吻合。在甲鞭毛虫中，亚历山大物种是该地区麻痹性贝类毒素（PST）的主要来源。在三个年代审查期间，Skagerrak-Kattegat中PST浓度均未超过规定水平，但在表层沉积物中经常有且经常有大量亚历山大静息囊肿发现，这表明有很高的潜在开花风险。挪威西海岸的PST水平通常高于法规限制，这与主要的毒素生产者-链霉菌（1型核糖体）有关。其他亚历山大藻物种，例如奥斯滕费尔德氏菌（A. ostenfeldii）和小茴香曲霉（A. minutum），能够在某些种群中产生PST，但通常与该地区的PSP事件无关。的细胞丰度鱼鳞毒素淋巴菌素（GD）的生产者伪gonyaulax（A. pseudogonyaulax）自2010年以来在Skagerrak-Kattegat地区有所增加，可能构成新的威胁。鞭毛藻二叠氮菌属。无疑与在北欧导致阿扎哌酸贝类中毒（AZP）的阿扎哌酸毒素（AZT）的存在有关。浓度高于在紫贻贝首次在挪威蓝贻贝和牡蛎监管限制在2005年和瑞典（双壳贝类中检测到这些毒素食用牡蛎和太平洋牡蛎在2018年硅藻属的某些成员）拟菱形藻产生神经毒素海藻酸及其类似物，称为失忆性贝类毒素（AST）。绽放在北海和Skagerrak-Kattegat中，假性尼兹菌很常见，但在审查期间，双壳贝类中AST的水平很少高于监管限度。在波罗的海，夏季的蓝藻花开引起人们的极大关注，主要是因为这会严重破坏沐浴水和海滩的污染。某些蓝细菌会产生毒素，例如，结节性结节杆菌结核菌素的生产者，这可能是人类健康问题，并偶尔导致狗死亡。北欧的沿海和陆架海域提供了重要的海鲜，社会经济福祉和生态系统服务。人为影响的增加和气候变化造成环境压力，导致生物地理学和HABs强度的变化。持续监测HAB和植物毒素以及HAEDAT等历史数据库的运行不仅提供了持续的状态报告，而且还提供了一种解释HAB的原因和机制的方法