Collaborative Research: Contribution of allochthonous DON to biological nitrogen demand in the subtropical North Pacific

合作研究：异地 DON 对北太平洋副热带生物氮需求的贡献

基本信息

批准号：
2343224
负责人：
Rene Boiteau
金额：
$ 38.01万
依托单位：
University of Minnesota-Twin Cities
依托单位国家：
美国
项目类别：
Continuing Grant
财政年份：
2024
资助国家：
美国
起止时间：
2024-07-01 至 2027-06-30
项目状态：
未结题

来源：
https://www.nsf.gov/awardsearch/showAward?AWD_ID=2343224&HistoricalAwards=false
关键词：
Collaborative Research Contribution allochthonous DON

项目摘要

Vast stretches of the ocean, covering almost 60% of its surface, are ‘deserts' where life struggles to survive due to nutrient scarcity. Located in the central gyres of the subtropical ocean, these regions are too remote to receive significant nutrient inputs from land or from deeper waters by vertical mixing. The low supply of nutrients should result in reduced levels of photosynthesis and less complex food webs. However, observations instead indicate that life grows at rates similar to regions which receive higher nutrient supplies. Our project seeks to determine what the missing sources of nutrients are that help sustain these ecosystems. This work will focus on nitrogen bound within dissolved organic molecules that are produced in nutrient-rich regions, including coastal California, and then transported laterally to the ‘ocean desert’ of the subtropical North Pacific Ocean. A one-month research expedition will leave from San Diego, CA and end in Honolulu, HI USA to study the production, accumulation, chemical composition, and utilization of dissolved organic nitrogen (DON) and link it to photosynthesis occurring across the North Pacific. The new knowledge gained about the role of DON in satisfying the nutrient requirements of the subtropical North Pacific will be used to construct computer models that gauge the global importance of this nutrient source to subtropical ocean ecosystems. Additional nitrogen (N) sources beyond subsurface nitrate (NO3-) and N2 fixation fluxes are required to explain observed net community production (NCP) within subtropical ocean ecosystems. Numerical models indicate that laterally supplied allochthonous DON may support 10-60% of NCP in oligotrophic subtropical gyres, but with large uncertainties. The proposed work will field test hypotheses concerning the biological production and consumption of marine DON, and whether allochthonous DON is a significant organic nutrient source sustaining NCP. A North Pacific cruise will use observations of DON concentration, chlorophyll a concentration, and N isotopes [DON's 15N/14N ratio, and NO3-'s 15N/14N ratio] to identify regions of net DON production and consumption in the context of net and gross biological productivity estimated using O2/Ar and triple Oxygen isotopic measurements, respectively. Novel organic geochemistry tools will be used to identify the molecular composition of the allochthonous DON. The influence of depth on DON consumption will be investigated using ship-board incubations that expose surface DON collected across gradients in surface NO3- to microbial communities from several depth intervals. Finally, a new semi-labile DON tracer will be encoded in a global ocean biogeochemistry model, fashioned to behave like the allochthonous DON characterized from the field observations. The DON and isotopic data sets will serve to constrain model parameterizations of semi-labile DON cycling. The state-of-the-art model of semi-labile DON cycling will be used to quantitatively assess the portion of NCP sustained by allochthonous DON delivery to the North Pacific subtropical gyre and extend this assessment across the global ocean.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.

占地近60％的海洋的巨大延伸是“沙漠”，由于营养稀缺，生命努力生存。这些区域位于亚热带海洋的中央回旋中，太遥远了，无法通过垂直混合从陆地或更深的水域接收大量的营养投入。养分的低供应应导致光合作用水平降低，食物网不太复杂。但是，观察结果表明，生命的增长率类似于获得更高养分供应的区域。我们的项目旨在确定缺失的营养来源是有助于维持这些生态系统的原因。这项工作将集中在溶解的有机分子中结合的氮，这些有机分子在包括沿海加利福尼亚在内的营养丰富地区生产的氮，然后横向运输到北太平洋亚热带的“海洋沙漠”。一个月的研究探险将从美国加利福尼亚州圣地亚哥离开，并在美国檀香山结束，以研究溶解有机氮（DON）的生产，积累，化学成分和利用，并将其与北太平洋地区发生的光合作用联系起来。关于DON在满足北太平洋亚热带养分需求中的作用的新知识将用于构建计算机模型，以评估这种营养源对亚热带海洋生态系统的全球重要性。除地下硝酸盐（NO3-）和N2固定通量以外的其他氮（N）来源需要解释亚热带海洋生态系统中观察到的净社区生产（NCP）。数值模型表明，侧向提供的异源DON可能支持少亲营的亚热带回旋中的10-60％的NCP，但具有较大的不确定性。拟议的工作将实地测试有关海洋DON的生物产生和消费的假设，以及Allochthonous Don是否是维持NCP的重要有机养分来源。 A North Pacific cruise will use observations of DON concentration, chlorophyll a concentration, and N isotopes [DON's 15N/14N ratio, and NO3-'s 15N/14N ratio] to identify regions of net DON production and consumption in the context of net and gross biologic productivity estimated using O2/Ar and triple Oxygen isotopic measurements, respectively.新型有机地球化学工具将用于识别异源DON的分子组成。深度对DON消耗的影响将使用船舶板孵化，这些船板孵化，从几个深度间隔中揭示了跨表面NO3梯度到微生物群落的表面DON的影响。最后，将在全球海洋生物地球化学模型中编码一个新的半规模唐·特拉克（Don Tracer），它的表现就像是从现场观测中所特征的同种唐。 DON和同位素数据集将用于限制半比例DON循环的模型参数。半比较的唐循环的最新模型将用于定量评估由异源Don交付到北太平洋亚热带陀螺仪所维持的NCP的部分，并将这一评估扩展到全球海洋中。该奖项反映了NSF的法定任务，并通过评估了基础的MERIT和BRODIT和BRODIT和BRODIT和BRODIT和BRODIT和BRODIT和BRODIT和BRODIT和BRODIT和BRODIT和BRODIT和BRODIT和BRODIT和广泛的影响。