Harmful algal blooms (HABs) are diverse phenomena involving multiple. species and classes of algae that occupy a broad range of habitats from lakes to oceans and produce a multiplicity of toxins or bioactive compounds that impact many different resources. Here, a review of the status of this complex array of marine HAB problems in the U.S. is presented, providing historical information and trends as well as future perspectives. The study relies on thirty years (1990–2019) of data in HAEDAT - the IOC-ICES-PICES Harmful Algal Event database, but also includes many other reports. At a qualitative level, the U.S. national HAB problem is far more extensive than was the case decades ago, with more toxic species and toxins to monitor, as well as a larger range of impacted resources and areas affected. Quantitatively, no significant trend is seen for paralytic shellfish toxin (PST) events over the study interval, though there is clear evidence of the expansion of the problem into new regions and the emergence of a species that produces PSTs in Florida – Pyrodinium bahamense. Amnesic shellfish toxin (AST) events have significantly increased in the U.S., with an overall pattern of frequent outbreaks on the West Coast, emerging, recurring outbreaks on the East Coast, and sporadic incidents in the Gulf of Mexico. Despite the long historical record of neurotoxic shellfish toxin (NST) events, no significant trend is observed over the past 30 years. The recent emergence of diarrhetic shellfish toxins (DSTs) in the U.S. began along the Gulf Coast in 2008 and expanded to the West and East Coasts, though no significant trend through time is seen since then. Ciguatoxin (CTX) events caused by Gambierdiscus dinoflagellates have long impacted tropical and subtropical locations in the U.S., but due to a lack of monitoring programs as well as under-reporting of illnesses, data on these events are not available for time series analysis. Geographic expansion of Gambierdiscus into temperate and non-endemic areas (e.g., northern Gulf of Mexico) is apparent, and fostered by ocean warming. HAB-related marine wildlife morbidity and mortality events appear to be increasing, with statistically significant increasing trends observed in marine mammal poisonings caused by ASTs along the coast of California and NSTs in Florida. Since their first occurrence in 1985 in New York, brown tides resulting from high-density blooms of Aureococcus have spread south to Delaware, Maryland, and Virginia, while those caused by Aureoumbra have spread from the Gulf Coast to the east coast of Florida. Blooms of Margalefidinium polykrikoides occurred in four locations in the U.S. from 1921–2001 but have appeared in more than 15 U.S. estuaries since then, with ocean warming implicated as a causative factor. Numerous blooms of toxic cyanobacteria have been documented in all 50 U.S. states and the transport of cyanotoxins from freshwater systems into marine coastal waters is a recently identified and potentially significant threat to public and ecosystem health.

Taken together, there is a significant increasing trend in all HAB events in HAEDAT over the 30-year study interval. Part of this observed HAB expansion simply reflects a better realization of the true or historic scale of the problem, long obscured by inadequate monitoring. Other contributing factors include the dispersion of species to new areas, the discovery of new HAB poisoning syndromes or impacts, and the stimulatory effects of human activities like nutrient pollution, aquaculture expansion, and ocean warming, among others. One result of this multifaceted expansion is that many regions of the U.S. now face a daunting diversity of species and toxins, representing a significant and growing challenge to resource managers and public health officials in terms of toxins, regions, and time intervals to monitor, and necessitating new approaches to monitoring and management. Mobilization of funding and resources for research, monitoring and management of HABs requires accurate information on the scale and nature of the national problem. HAEDAT and other databases can be of great value in this regard but efforts are needed to expand and sustain the collection of data regionally and nationally.

有害藻华 (HAB) 是涉及多种因素的多种现象。藻类的种类和类别占据了从湖泊到海洋的广泛栖息地，并产生多种毒素或生物活性化合物，影响许多不同的资源。本文对美国一系列复杂的海洋有害细菌问题的现状进行了回顾，提供了历史信息和趋势以及未来的前景。该研究依赖于HAEDAT（IOC-ICES-PICES有害藻类事件数据库）三十年（1990-2019）的数据，但还包括许多其他报告。从定性的角度来看，美国国家HAB问题比几十年前的情况要广泛得多，需要监测的有毒物种和毒素更多，受影响的资源和受影响的区域范围也更大。从数量上看，在研究期间，麻痹性贝类毒素（PST）事件没有出现明显的趋势，尽管有明确的证据表明该问题已扩展到新的地区，并且在佛罗里达州出现了一种产生 PST 的物种——巴哈马吡咯汀。美国遗忘性贝类毒素（AST）事件显着增加，总体格局是西海岸频繁爆发，东海岸新出现、反复爆发，墨西哥湾零星发生。尽管神经毒性贝类毒素 (NST) 事件有着悠久的历史记录，但在过去 30 年中没有观察到明显的趋势。美国最近出现的腹泻性贝类毒素 (DST) 始于 2008 年墨西哥湾沿岸，并扩展到西海岸和东海岸，但此后没有看到明显的趋势。由甘比尔鞭毛虫引起的雪卡毒素 (CTX) 事件长期以来影响着美国的热带和亚热带地区，但由于缺乏监测计划以及疾病报告不足，这些事件的数据无法用于时间序列分析。甘比尔鞭毛虫向温带和非流行地区（例如墨西哥湾北部）的地理扩张是显而易见的，并且受到海洋变暖的促进。与 HAB 相关的海洋野生动物发病率和死亡率事件似乎正在增加，在加利福尼亚州沿海的 AST 和佛罗里达州的 NST 引起的海洋哺乳动物中毒中观察到统计显着的增加趋势。自 1985 年在纽约首次出现以来，由金球菌高密度繁殖引起的褐潮已向南蔓延到特拉华州、马里兰州和弗吉尼亚州，而由金黄色藻引起的褐潮则从墨西哥湾沿岸蔓延到佛罗里达州东海岸。Margalefidinium polykrikoides的花朵1921年至2001年期间，在美国的四个地点发生过这种情况，但此后又出现在超过15个美国河口，海洋变暖被认为是其致病因素。美国所有 50 个州都记录了大量有毒蓝藻的繁殖，最近发现蓝藻毒素从淡水系统输送到沿海水域是对公众和生态系统健康的潜在重大威胁。

总而言之，在 30 年的研究间隔内，HAEDAT 中的所有 HAB 事件均呈显着增加趋势。观察到的HAB扩张部分反映了人们更好地认识到问题的真实或历史规模，而长期以来由于监测不足而被掩盖。其他影响因素包括物种向新地区的扩散、新的 HAB 中毒综合症或影响的发现，以及营养物污染、水产养殖扩张和海洋变暖等人类活动的刺激效应。这种多方面扩张的结果之一是，美国许多地区现在面临着令人畏惧的物种和毒素多样性，这对资源管理者和公共卫生官员在毒素、区域和监测时间间隔方面构成了重大且日益严峻的挑战。需要新的监测和管理方法。调动资金和资源用于有害生物的研究、监测和管理需要有关国家问题的规模和性质的准确信息。HAEDAT 和其他数据库在这方面可能具有巨大价值，但需要努力扩大和维持区域和国家数据收集。