Doctoral Dissertation Research: Dissolved organic nitrogen uptake by harmful algal blooms in the Chukchi Sea

当藻类群落的生长威胁到人类和/或生态系统的健康时，就会发生有害藻华（HABs）。一些有害藻华涉及产生强效神经毒素的藻类，可以伤害贝类、海洋哺乳动物、海鸟和其他重要资源。在过去的15年里，有毒的赤潮已经在太平洋和北冰洋被观察到，并对依赖狩猎和捕鱼为生的土著和其他当地社区构成潜在威胁。该项目补充了伍兹霍尔海洋研究所（WHOI）的科学家们在一次研究巡航中收集的数据，以更好地了解促进这些水华的因素。研究小组通过分析楚科奇海中不同的氮化合物，以及不同种类的藻类吸收这些化合物的速度，来确定形成有害藻华的藻类是否比其他藻类更善于利用溶解有机氮（DON）来生长。调查人员正在与更广泛的WHOI团队合作，通过小册子、公开讲座、电台采访以及与土著社区、当地科学家和当地官员的讨论，传播研究结果及其对阿拉斯加社区和沿海管理的影响。该项目还通过斯坦福大学地球科学与工程本科研究项目培训了一名本科生和斯坦福大学的两名研究生。该项目补充了由伍兹霍尔海洋研究所（WHOI）科学家领导的研究巡航期间收集的其他测量数据。这次巡游的主要目标是更好地了解促进这些水华的因素。该项目正在研究一种假设，即鞭毛藻HAB物种对DON的偏好超过溶解的无机氮，这有助于它们在楚科奇海（Chukchi Sea） 7月和8月的成功，楚科奇海是夏季已知氮有限的地区。研究人员将对楚科奇海的DON浓度进行采样，并将其与赤潮分布联系起来。科考船上将进行一系列15n标记示踪剂孵育，以测量整个浮游植物群落对硝酸盐、铵、尿素和溶解的游离氨基酸的整体吸收率。测量单个细胞同位素组成的纳米二级离子质谱法将用于确定来自相同孵育的单细胞氮摄取率。由于传统上认为硅藻是楚科奇海中形成水华的主要浮游植物，因此将对赤潮藻类和以赤潮藻类为主的群落的氮吸收与硅藻和以硅藻为主的群落的氮吸收进行比较。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Harmful algal blooms (HABs) happen when the growth of colonies of algae threaten human and/or ecosystem health. Some HABs involve algae that produce potent neurotoxins that can harm shellfish, marine mammals, seabirds, and other critical resources. In the past 15 years, toxic HABs have been observed in the Pacific Arctic Ocean and pose a potential threat to Indigenous and other local communities that depend on hunting and fishing for food. This project supplements data collected during a research cruise led by scientists from the Woods Hole Oceanographic Institution (WHOI) to better understand the factors promoting these blooms. The team is determining whether algae that form HABs are better than other algae at using dissolved organic nitrogen (DON) for growth by characterizing different nitrogen compounds in the Chukchi Sea and how quickly various algae species take up these compounds. The investigators are collaborating with the broader WHOI team to communicate the research results and their implications for Alaskan communities and coastal management via brochures, public lectures, radio interviews, and discussions with Indigenous communities, local scientists, and local officials. The project is also training one undergraduate student through the Stanford Undergraduate Research in Geoscience and Engineering program and two graduate students at Stanford University.This project complements other measurements collected during a research cruise led by scientists from the Woods Hole Oceanographic Institution (WHOI). The principal cruise goal is to better understand the factors promoting these blooms. This project is examining the hypothesis that the preference for DON over dissolved inorganic nitrogen by dinoflagellate HAB species contributes to their success in July and August in the Chukchi Sea, an area that is known to be nitrogen-limited in the summer. The investigators will sample DON concentrations across the Chukchi Sea and relate them to HAB distributions. A series of 15N-labelled tracer incubations will be conducted onboard the research vessel to measure bulk uptake rates of nitrate, ammonium, urea, and dissolved free amino acids by the entire phytoplankton community. Nanoscale secondary ion mass spectrometry, which measures individual cell isotopic composition, will be used to determine single-cell nitrogen uptake rates from the same incubations. Nitrogen uptake by HAB species and HAB-dominated communities will be compared to that of diatom species and diatom-dominated communities, as diatoms are traditionally considered the dominant bloom-forming phytoplankton in the Chukchi Sea.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.