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

当藻类群体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(HAB)。一些赤潮涉及产生强烈神经毒素的藻类，这些毒素可以损害贝类、海洋哺乳动物、海鸟和其他关键资源。在过去的15年里，在太平洋北冰洋发现了有毒的赤潮，对以狩猎和捕鱼为食物的土著和其他当地社区构成了潜在威胁。该项目补充了伍兹霍尔海洋研究所(WHOI)科学家领导的一次研究巡航期间收集的数据，以更好地了解推动这些水华爆发的因素。该团队正在通过表征楚科奇海的不同氮化合物来确定形成赤潮的藻类在利用溶解有机氮(DON)生长方面是否比其他藻类更好，以及各种藻类吸收这些化合物的速度有多快。研究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，交流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两名斯坦福大学的研究生。该项目是对伍兹霍尔海洋研究所(WHOI)科学家领导的一次研究巡航期间收集的其他测量数据的补充。巡航的主要目标是更好地了解促进这些水华的因素。该项目正在检验这样一种假设，即甲藻HAB物种对DON的偏好比溶解的无机氮更有助于它们在7月和8月在楚科奇海取得成功，该地区是众所周知的夏季氮素有限的地区。研究人员将对楚科奇海的DON浓度进行采样，并将其与HAB的分布联系起来。将在科考船上进行一系列15N标记的示踪剂培养，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速率。测量单个细胞同位素组成的纳米级二次离子质谱仪将被用来确定相同培养条件下的单细胞氮摄取率。由于硅藻传统上被认为是楚科奇海形成水华的主要浮游植物，因此HAB物种和以HAB为主的群落的氮素吸收将与硅藻物种和以硅藻为主的群落的氮素吸收进行比较。这一奖项反映了NSF的法定使命，并通过使用基金会的智力优势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.