Quantifying Iron Turnover in the Upper Ocean via Time-series Measurements at Station ALOHA

通过 ALOHA 站的时间序列测量量化上层海洋的铁周转率

• 批准号: 2022969
• 负责人: Nicholas Hawco
• 金额: $ 46.02万
• 依托单位: University of Hawaii
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2020
• 资助国家: 美国
• 起止时间: 2020-09-01 至 2024-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2022969&HistoricalAwards=false
• 关键词: Quantifying; Iron; Turnover; Upper; Ocean

Phytoplankton are the base of marine food webs but their ability to grow in the open ocean by photosynthesis is limited by the scarcity of key nutrients especially iron. To understand how phytoplankton respond to global environmental changes, it is essential to predict how the nutrient content of seawater will change as well. Iron is essential to the light-harvesting machinery of phytoplankton but is an extremely small fraction of seawater (1 part per billion) . Iron is much more abundant in soils and when dust storms blow these soils out to sea, the iron content of seawater increases. It is unknown how long the effects of these iron supply events last, which depends on how well the marine ecosystem can recover and reuse iron before it sinks to the seafloor. It is also unknown if human activities have added to the natural Fe supply. The proposed research will address these questions by conducting a 3 year time-series of iron measurements in the North Pacific Ocean. Here, dust supply from Asia occurs mainly during spring, allowing the loss of iron over the summer and fall months to be documented. Unique chemical signatures will be used to distinguish iron supply from the deposition of desert dust or from human sources. This record of the marine iron cycle will be important for validating ecosystem models that are used to predict how climate change will influence the growth of phytoplankton in the future. The research would make a scientific contribution to the Hawaii Ocean Time-Series, help improve biogeochemical iron models, student training at the graduate and undergraduate level, and support an early career scientist. A 3 year time-series of iron (Fe) measurements is proposed to constrain the magnitude of external Fe input and Fe recycling in the open ocean. Near-monthly observations will be conducted in the North Pacific Subtropical Gyre onboard Hawaii Ocean Timeseries cruises, which receives regular dust input during springtime and is minimally influenced by deep mixing. Water column profiling of dissolved and particulate Fe concentrations – combined with the flux of Fe recorded in trace-metal-clean sediment traps – will define a residence time of Fe in the upper water column. Iron uptake rates will be quantified through short-term incubations using a novel stable isotope technique and will be used to derive a turnover time with respect to biological uptake. Finally, the isotopic composition of dissolved and particulate Fe in the mixed layer will be measured to evaluate the potential importance of anthropogenic and Hawaiian Fe sources, which are poorly constrained. Together, these measurements will define the tempo and variability of the open ocean Fe cycle and provide a means to validate models that simulate the biogeochemistry of this key micronutrient.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.

浮游植物是海洋食品网的基础，但它们通过光合作用在开阔的海洋中生长的能力受到关键营养素（尤其是铁）的稀缺的限制。为了了解浮游植物如何应对全球环境变化，必须预测海水的营养含量也将如何变化。铁对于浮游植物的轻度收获机制至关重要，但仅是海水的一小部分（十亿分之一）。铁在土壤中的丰富程度要大得多，当沙尘暴将这些土壤吹向海洋时，海水的铁含量就会增加。这些铁供应事件的效果持续了多长时间，这取决于海洋生态系统能够恢复和重复使用铁之前的效果。人类活动是否增加了自然供应量也未知。拟议的研究将通过在北太平洋进行三年的铁测量时间来解决这些问题。在这里，亚洲的尘埃供应主要发生在春季期间，允许在夏季和秋季几个月中丧失铁。独特的化学特征将用于将铁供应与沙漠灰尘的沉积或人类来源区分开。海洋铁循环的记录对于验证用于预测气候变化将来如何影响浮游植物的生长的生态系统模型将很重要。该研究提出了三年的铁（FE）测量时间序列，以限制开阔的外部FE输入和Fe回收的大小。将在北太平洋亚热带Gyre夏威夷海洋时间巡游中进行接近月份的观察，该巡航会在春季收到常规的灰尘输入，并受到深层混合的影响。水柱的溶解和特定Fe浓度的分析 - 结合了痕量金属清洁沉积物陷阱中记录的Fe的通量 - 将定义上水柱中Fe的停留时间。铁吸收率将通过短期孵育使用新型稳定同位素技术来量化，并将用于在生物学摄取方面得出周转时间。最后，将测量混合层中溶解和特定FE的同位素组成，以评估人为和夏威夷FE来源的潜在重要性，这些源是受限制不佳的。这些测量结果将共同定义开放海洋FE周期的节奏和变异性，并提供了一种验证模型的方法，以模拟该关键微量营养素的生物地球化学。该奖项反映了NSF的法定任务，并被认为是值得通过基金会的知识分子优点和更广泛影响的审查审查标准来通过评估来通过评估来支持的。

项目成果

Recycling of dissolved iron in the North Pacific Subtropical Gyre

• DOI: 10.1002/lno.12212
• 发表时间: 2022-09
• 期刊: Limnology and Oceanography
• 影响因子: 4.5
• 作者: N. Hawco;Shun‐Chung Yang;P. Pinedo‐González;Erin E. Black;J. Kenyon;S. Ferrón;X. Bian;S. John