Collaborative Research: A High Resolution Multi-Tracer Biogeochemical Study of the Pacific Arctic

北极的地表变暖速度大约是全球平均速度的两倍，导致海冰范围和厚度减少，北冰洋大部分地区季节性开放水域的时间延长。需要对太平洋北极地区，包括北方白令海和楚科奇海进行直接观测，以了解这一生态系统在快速变化的时期是如何变化的。为此，调查人员将参加计划于2020年夏季进行的研究考察，并将同时对溶解氧、溶解二氧化碳、溶解营养物、颗粒有机物分布和组成以及浮游生物生产力进行海洋学测量。除了提供关于该区域生物和物理过程的新信息外，这些观测还将补充和扩大伍兹霍尔海洋研究所合作者开展的关于该区域有害藻华物种的分布和活动的配套项目，这是阿拉斯加社区的一个紧急关切。这项研究将支持研究生和本科生，为他们提供研究和体验教育的机会。研究人员将参加在阿拉斯加举行的区域会议和研讨会，向更广泛的受众传达他们的发现。为了测试与太平洋北极地区元素循环和生产力的控制和时空模式相关的假设，研究人员将测量一套新的生态系统相关示踪剂，这些示踪剂以高频率从美国海岸警卫队切割机希利正在进行的系统和CTD调查中取样。他们将同时对溶解的硝酸盐和磷进行高分辨率测量，以评估营养动态、氧氩比和二氧化碳分压，以确定净群落生产和生物介导的海-气二氧化碳交换，以及颗粒有机物浓度和颗粒光学特性。（颗粒大小、光束衰减和叶绿素荧光）来量化浮游植物生物量和大小结构的趋势。此外，研究人员将使用三重氧同位素技术和碳-13/氮-15吸收孵育来确定初级生产力的速率，以及快速重复率荧光测定法来评估浮游植物在可变环境条件下的营养状况。这种多示踪剂方法将区分不同的过程（例如，平流、上升流和混合）及其生物地球化学/生态响应（例如，该奖项反映了NSF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。

Surface warming is occurring in the Arctic at a pace that is roughly double that of the global average, leading to reductions in extent and thickness of sea ice and prolonged seasonal periods of open water throughout much of the Arctic Ocean. Direct observations in the Pacific Arctic region, including the northern Bering and Chukchi seas, are needed to understand how this ecosystem is shifting in a time of rapid change. To that end, the investigators will participate in a research expedition scheduled for summer 2020 and will make simultaneous oceanographic measurements of dissolved oxygen, dissolved carbon dioxide, dissolved nutrients, particulate organic matter distribution and composition, and plankton productivity. In addition to providing new information about biological and physical processes in the region, these observations will complement and extend a companion project conducted by collaborators from the Woods Hole Oceanographic Institution about the distribution and activity of harmful algal bloom species in the region, which are an emergent concern for Alaskan communities. This study will support graduate and undergraduate students, providing them research and experiential educational opportunities. The investigators will attend regional meetings and seminars in Alaska to communicate their findings to broader audiences.To test hypotheses related to the controls and spatial-temporal patterns in elemental cycling and productivity of the Pacific Arctic, the investigators will measure a novel suite of ecosystem-relevant tracers, sampled at high frequency from the US Coast Guard Cutter Healy's underway system and from CTD surveys. They will make simultaneous, high resolution measurements of dissolved nitrate and phosphorous to evaluate nutrient dynamics, oxygen-argon ratios and partial pressure of carbon dioxide to determine net community production and biologically-mediated air-sea carbon dioxide exchange, and particulate organic matter concentrations and particle-optical properties (particle size, beam attenuation and chlorophyll fluorescence) to quantify trends in phytoplankton biomass and size structure. In addition, the investigators will use the triple oxygen isotope technique and carbon-13/nitrogen-15 uptake incubations to determine rates of primary productivity, as well as Fast Repetition Rate Fluorometry to evaluate phytoplankton nutritional status under variable environmental conditions. This multi-tracer approach will discriminate different processes (e.g., advection, upwelling and mixing) and their biogeochemical/ecological response (e.g., productivity, respiration, export, and shifts in community composition) at fine temporal and spatial scales.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.