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

有害藻华（HABs）发生时，藻类群体的生长威胁人类和/或生态系统的健康。有些有害藻华涉及产生强效神经毒素的藻类，这些毒素会危害贝类、海洋哺乳动物、海鸟和其他重要资源。在过去15年中，在太平洋北冰洋观察到有毒的有害生物，对依靠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数据，以更好地了解促进这些水华的因素。该团队正在确定形成HAB的藻类是否比其他藻类更好地利用溶解有机氮（DON）进行生长，方法是描述楚科奇海中不同的氮化合物以及各种藻类吸收这些化合物的速度。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，广播采访以及与土著社区，当地科学家和当地官员的讨论来传达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和工程本科生研究方案培训一名本科生，并在斯坦福大学培训两名研究生，该项目补充了伍兹霍尔海洋研究所科学家领导的研究航行期间收集的其他测量数据。 巡航的主要目标是更好地了解促进这些水华的因素。 该项目正在研究的假设，DON溶解无机氮的甲藻HAB物种的偏好有助于他们的成功，在7月和8月在楚科奇海，一个地区，是已知的氮在夏季有限。研究人员将在楚科奇海对DON浓度进行采样，并将其与HAB分布联系起来。将在研究船上进行一系列15 N标记的示踪剂孵育，以测量整个浮游植物群落对硝酸盐、铵、尿素和溶解游离氨基酸的大量吸收率。测量单个细胞同位素组成的纳米级二次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形成水华的主要浮游植物，因此将把有害藻种和以有害藻为主的群落的氮吸收与硅藻种和以硅藻为主的群落的氮吸收进行比较，这一奖项反映了NSF的法定使命，并被认为值得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予以支持。

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.