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

美国和世界上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。人为的营养负荷与不断扩大的赤潮发病率有关，但这种关系是特定地点和特定生物体的，目前仍知之甚少。这方面的主要挑战是确定自然营养源与人为营养源在单个赤潮生物物种发展过程中的相对重要性。在这个项目中，伍兹霍尔海洋研究所和奥斯汀的德克萨斯大学的研究小组将采取一种新的方法来应对这一挑战：他们使用一种特定物种的HAB毒素的氮同位素特征(Del15N)来识别促进细胞生长和毒素产生的氮源和化学形式。形成水华的亚历山大藻(Alexandrium Fundyense)及其生物活性化合物--腐霉毒素(STX)是一个理想的模式系统，因为STX富含氮，通常只由单一物种在混合浮游生物组合中产生。总的指导性假设是，HAB特定毒素的同位素特征可用于区分人为和自然的N来源，并提供比散装材料del15N更多的关于导致特定有毒物种大量繁殖的N的来源、化学形式和加工的细节。这一假设是基于这样一种原理，即相对于集水水中的自然氮来源，地下水和污水中的人类和动物排泄物变得富含15N，而无机肥料变得贫乏15N。虽然使用散装生物量的同位素比率del15N来确定沿海水域的氮源是一种被广泛接受的做法，但这种使用毒素作为特定物种的示踪剂或标记是新的，它将提供导致特定赤潮物种水华的氮素的明确来源、化学形态和加工的细节。更广泛的影响：该项目解决了所有HAB中毒综合征中最普遍的麻痹性贝类中毒(PSP)的根本问题，PSP是影响世界各国的一种主要贝类中毒形式。项目成果还可以帮助有关污染控制和其他水华缓解战略的政策决策，并可应用于一系列赤潮生物物种--那些产生萨克毒素的物种，以及那些产生其他富含氮的毒素的物种。项目成果将通过科学论文、在讲习班上的陈述、国内和国际会议、部门研讨会以及与媒体的讨论等方式广泛传播。

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.