Collaborative Research: Quantifying the Relationship between Nitrogen Uptake and Net Community Production using a Synthesis of JGOFS Data and 1-D Modeling

群落净生产量(NCP)的测量是对海洋表层水域产生的有机物质数量的可靠估计。NCP可以作为建立表层水碳输出模型和海洋吸收大气二氧化碳能力模型的起点。然而，大多数海洋生产模型是基于磷或氮等限制营养物质的，因此这类模型的可靠性将取决于海洋将限制营养物质的消耗转换为二氧化碳吸收的精确度。PIs将校准NCP和新的(硝酸盐)产量之间的关系，以帮助实现预测海洋作为碳汇的作用的目标。如何最好地在表层海洋元素循环之间转换的问题将被研究，零假设是在海洋温跃层水域中发现的化学计量比(雷德菲尔德比)是在氮和NCP之间转换的定量方法。将使用比较方法来检查表面氮循环和碳循环之间的耦合程度。在碳和氮在雷德菲尔德意义上似乎没有耦合的情况下，将仔细评估可能的方法原因。根据这一分析，早期开花对营养限制条件的作用；优势类群；溶解有机物(DOM)水平；氮固定；铁限制和其他因素将被认为是改变氮和碳通量之间关系的因素。具有代表性的海洋区域的耦合程度将在一个具有现实上层物理的一维数值模式中进行评估。这些结果将使生物地球化学模型师能够判断何时使用雷德菲尔德比率进行转换是适当的，并确定哪些情况(如果有的话)适合采用替代转换方法。这将有助于对对相关生物过程敏感的碳通量进行更准确的预测。

Sambrotto The measurement of Net Community Production (NCP) is a robust estimate of the amount of organic material produced in surface waters of the ocean. NCP can serve as a starting point for models of carbon export from surface waters and the ocean's capacity to absorb carbon dioxide from the atmosphere. However, most models of ocean production are based on a limiting nutrient such as phosphorus or nitrogen and the reliability of this class of models therefore will depend on how accurately the consumption of limiting nutrients can be converted to the absorption of carbon dioxide by the ocean. The PIs will calibrate the relationship between NCP and new (nitrate) production in order to assist in the goal of predicting the role of the ocean as a carbon sink. The question of how to best convert between surface ocean elemental cycles will be examined with the a null hypothesis being that the stoichiometric oxidative ratios found in ocean thermocline waters (the Redfield ratios) are a quantitative way to translate between nitrogen and NCP. A comparative approach will be used to examine the extent of coupling between the surface nitrogen and carbon cycles. In instances where carbon and nitrogen appear to be uncoupled in the Redfield sense, possible methodological causes will be carefully evaluated. Following this analysis, the role of early bloom vs. nutrient limited conditions; dominant taxa; dissolved organic matter (DOM) levels; N2 fixation; iron limitation and other factors will be considered as agents modifying the relationship between nitrogen and carbon fluxes. The degree of coupling in representative ocean regions will be evaluated in a one-dimensional numerical model with realistic upper layer physics. These results will allow biogeochemical modelers to judge when the use of Redfield ratios for conversion is appropriate and identify what (if any) circumstances merit an alternate conversion approach. This will contribute to more accurate predictions of carbon flux that are sensitive to the relevant biological processes.