Collaborative Research: Identification of nitrogen sources for toxic Alexandrium blooms using a novel species-specific tracer, d15N-saxitoxin

美国和世界其他国家都受到有害藻华（HAB）的影响，对人类健康，海洋生态系统，渔业资源和当地经济产生负面影响。人为的营养负荷已与扩大赤潮发病率，但关系是网站和生物体的具体，仍然知之甚少。在这方面的主要挑战是确定自然与人为营养源在发展单个有害藻华物种方面的相对重要性。由于有害赤潮发生的浮游生物组合的多样性，以及缺乏适当的测量技术，这是非常困难的。在这个项目中，伍兹霍尔海洋研究所和德克萨斯大学奥斯汀分校的研究小组将采取一种新颖的方法来应对这一挑战：他们使用特定物种HAB毒素的氮同位素特征（del 15 N）来识别促进细胞生长和毒素产生的氮源和化学形式。水华形成的甲藻芬迪亚历山大藻及其一类生物活性化合物石房蛤毒素（STX）是理想的模型系统，因为STX富含氮，并且通常仅由混合浮游生物组合中的单一物种产生。 指导性的总体假设是，一个赤潮特异性毒素的同位素签名可以用来区分人为和自然来源的N和提供更多的细节比散装材料del 15 N的来源，化学形式和加工的N，导致一个特定的有毒物种的水华。这一假设是基于这样的原则，即相对于集水沃茨中的自然氮源，地下水和污水中的人类和动物废物成为15 N富集和无机肥料15 N贫化。虽然使用大量生物质的同位素比率del 15 N来确定沿海沃茨的氮源是一种被广泛接受的做法，但使用毒素作为物种特异性示踪剂或标记物是一种新的做法，将提供有关导致特定赤潮物种大量繁殖的氮的明确来源、化学形式和加工过程的详细信息。更广泛的影响：该项目处理所有有害藻华中毒综合症中最普遍的麻痹性贝类中毒的根本问题，麻痹性贝类中毒是影响世界各国的一种主要的贝类中毒形式。项目成果还可协助作出关于污染控制和其他水华缓解战略的政策决定，并可应用于一系列有害藻华物种-产生石房蛤毒素的物种以及产生其他富氮毒素的物种。项目成果将通过科学论文、在讲习班、国内和国际会议、部门研讨会上的介绍以及与媒体的讨论广泛传播。

The US and other countries throughout the world are affected by harmful algal blooms (HABs) that negatively impact human health, marine ecosystems, fisheries resources, and local economies. Anthropogenic nutrient loadings have been linked to expanding HAB incidence, but the relationship is site- and organism-specific, and is still poorly understood. The main challenge in this regard is to determine the relative importance of natural versus anthropogenic nutrient sources in the development of an individual HAB species. Given the diverse nature of the planktonic assemblage in which HABs occur, and the lack of appropriate measurement techniques, this is exceedingly difficult to accomplish.In this project, research teams at the Woods Hole Oceanographic Institution and University of Texas at Austin will take a novel approach to this challenge: They use use the nitrogen isotopic signature (del15N) of a species-specific HAB toxin to identify the nitrogen source and chemical form that promotes cell growth and toxin production. The bloom-forming dinoflagellate Alexandrium fundyense and its class of bioactive compounds, saxitoxins (STXs), are an ideal model system as STXs are nitrogen-rich and are typically only produced by a single species in mixed plankton assemblages. The guiding overall hypothesis is that the isotopic signature of a HAB-specific toxin can be used to discriminate between anthropogenic and natural sources of N and provide more details than bulk material del15N on the source, chemical form, and processing of N that lead to blooms of a particular toxic species. This hypothesis is based on the principle that human and animal waste in groundwater and sewage become 15N-enriched and inorganic fertilizers 15N-depleted, relative to natural sources of N in catchment waters. While the use of the isotopic ratio del15N of bulk biomass to identify nitrogen sources to coastal waters is a widely accepted practice, this use of a toxin as a species-specific tracer or marker is new and will provide details on the explicit source, chemical form, and processing of nitrogen that results in blooms of a particular HAB species. Broader Impacts: This project addresses fundamental issues underlying the most widespread of all HAB poisoning syndromes, paralytic shellfish poisoning (PSP), a major form of shellfish poisoning that affects countries throughout the world. Project results can also assist in policy decisions about pollution control and other bloom mitigation strategies, and can be applied to a range of HAB species - those that produce saxitoxins, as well as those that produce other toxins that are nitrogen rich. Project results will be broadly disseminated through scientific papers, presentations at workshops, domestic and international conferences, and departmental seminars, and discussions with the media.