In-situ Rates of Gross Primary Production, Respiration, and Net Community Production in the Subtropical N. Pacific

海洋初级生产速率、群落呼吸速率和净群落生产速率是了解大气向深海输送碳的重要基础。然而，瓶孵育方法固有的缺陷，特别是瓶孵育的时间尺度与生物群落对水体变化条件的反应之间的不匹配，引发了海洋低营养区是净自养还是异养的持续争论。由于体外技术可能错过高产期，瓶培养方法固有的潜在偏见是向异养。氧同位素法（OIM）是一种新开发的方法，其优点是不需要瓶孵育，因此对传统上用于估计海洋初级产量和净群落产量的14C和O2瓶孵育方法固有的体外与原位不确定性不敏感。其次，OIM产率综合了O2在混合层中停留10-20天的时间，这意味着与孵化方法相比，OIM错过初级生产事件的可能性要小得多。在这项研究中，来自华盛顿大学的一名研究人员将使用OIM来提高我们对初级产量和净群落产量的时间变异性的理解，并通过测量氧同位素的自然丰度和溶解O2/Ar气体的比率，估算夏威夷ALOHA站的原位总初级产量、群落呼吸和净群落产量的月速率，来测试海洋异养的假设。根据研究人员在ALOHA站的初始氧同位素和O2/Ar测量，用氧同位素方法测量的原位总初级产量平均是基于14c估计的初级产量的两倍多。因此，预计ALOHA每年综合的原位总初级生产量和净群落生产量将超过总初级生产量和净群落生产量的体外比率，并表明净自养。如果是这样，这将是对假设的正检验。随着OIM的测量，PI将比较基于OIM的总初级产量和净群落产量与由14C瓶孵育、快速重复率荧光法测量、生物光学模型、由系泊式O2传感器测量的表层原位O2的连续记录，以及基于卫星的叶绿素和初级生产的变异估计，以与现有的初级生产测量技术提供完整的相互校准。就更广泛的影响而言，拟议中的研究将改进对海洋生物泵的估计，如果海洋生物泵因全球变暖而发生变化，将影响大气中二氧化碳的积累速度。拟议的研究将增加一个重要的数据集，每月估计亚热带北太平洋的初级产量和净群落产量，可用于广泛的海洋学社区，并与ALOHA测量的长达十年的14c初级产量数据集进行比较。本科生和研究生都将参与这个项目。通过同位素样品制备系统的自动化，设备基础设施将得到加强。

ABSTRACTOCE-0525843Rates of primary production, community respiration, and net community production in the ocean are crucial underpinnings to understand the biological pump of carbon from the atmosphere to the deep sea. However, the inherent deficiencies with bottle incubation methods, especially the mismatch between the timescales of bottle incubations and the response of biological communities to changing conditions in the water column, has fueled an ongoing debate whether oligotrophic regions of the ocean are net autotrophic or heterotrophic. Since the in vitro techniques can miss episodes of high productivity, the inherent potential bias in bottle incubation methods is towards heterotrophy. A newly developed method, the oxygen isotope method (OIM) has the advantage of not requiring bottle incubations and thus is not sensitive to the in vitro versus in situ uncertainty inherent to the 14C and O2 bottle incubation methods traditionally used to estimate primary production and net community production in the ocean. Second, the OIM yields rates that integrate over the 10-20 day residence time of O2 in the mixed layer which means that the OIM is much less likely to miss primary production events compared to incubation methods. In this study, a researcher from the University of Washington will use the OIM to improve our understanding of the temporal variability in primary production and net community production, and test the hypothesis of oceanic heterotrophy by estimating monthly rates of in situ gross primary production, community respiration, and net community production off Hawaii at station ALOHA using measurements of the natural abundance of oxygen isotopes and the ratio of dissolved O2/Ar gases. Based on the investigator's initial oxygen isotope and O2/Ar measurements at station ALOHA, in situ gross primary production measured by the oxygen isotope method was on average more than twice the 14C-based estimates of primary production. Annually integrated in situ gross primary production and net community production rates at ALOHA are therefore expected to exceed the in vitro rates of gross primary production and net community production and indicate net autotrophy. If so, this would be positive test of the hypothesis. Along with the OIM measurements, the PI will compare the OIM-based rates of gross primary production and net community production to independent primary production estimates determined from 14C bottle incubations, Fast Repetition Rate Fluorometry measurements, a bio-optical model, a continuous record of surface layer in situ O2 measured by a moored O2 sensor and satellite-based estimates of variability in chlorophyll and primary production to provide a complete intercalibration with extant techniques for primary production measurements. Concerning the broader impacts, the proposed research will improve estimates of the ocean's biological pump, which if it should change in response to global warming, would affect the rate of atmospheric CO2 build-up. The proposed research will add a significant dataset of monthly estimates of primary production and net community production in the subtropical N. Pacific that can be used by the broad oceanographic community and compared to the decade-long dataset of 14C-primary production measured at ALOHA. There will be both undergraduate and graduate student involvement in the project. Equipment infrastructure will be enhanced through the automation of the isotope sample preparation system.