Primary Production Rates in the N. Pacific from Oxygen Isotope Measurements

在这项研究中，华盛顿大学的研究人员将通过测量溶解氧的同位素组成和饱和水平来确定北太平洋的总初级生产力和净初级生产力的原位速率。海洋生产力影响地球的一系列基本特性，例如，大气中二氧化碳和氧气的浓度，以及潜在渔业产量的大小。在不久的将来，潜在的气候变化引起的海洋生产力变化可能会反馈到大气中人为二氧化碳积累速度的变化。总而言之，我们量化海洋生产力速率的能力对于我们理解地球的碳循环在过去和未来将如何变化至关重要。海洋的初级生产力(PP)比率历来是通过瓶子中的比率测量来确定的。然而，瓶装PP的测量在一定程度上受到了体外条件和原位条件之间的不平等的影响。此外，到目前为止最常见的体外PP方法--~(14)C摄取得出的PP估计值，面临着额外的不确定性，即这些速率是代表总PP还是代表净PP。在一个经典的比较中，从地下对氧气利用率的估计间接得出的碳出口速率是基于14C的初级生产力测量结果的两倍(Jenkins和Goldman，1985)。这些不确定性强调了使用不依赖于瓶子培养的方法来确定PP率的必要性。最近开发了一种新的技术来估计海洋中的总PP和净PP(Luz和Barkan，2000)。它依赖于对溶解的O2的同位素组成的极其精确的测量。这种方法的优点是它不需要瓶子孵化。在这项研究中，首席研究人员将使用这种氧同位素方法来现场测定北太平洋地区PP的总量和净化率，并将这些速率与使用14C和18O标记技术进行瓶装PP测量进行比较。研究小组将在亚热带(Aloha站)和亚极(海洋站Papa)北太平洋的两个JGOFS时间序列站点进行这些测量。这两个地点都有10年或更长时间的基于14C的生产率数据，可以与这种新方法确定的现场PP估计进行比较。这两个站点的PP速率测量的时间历史，这些站点多年来对碳出口的几种估计(例如，沉积物陷阱、O2收支、DIC收支、234Th收支等)，以及这两个站点(高营养与低营养)的生物地球化学状况的对比，使北太平洋成为扩大氧同位素方法应用的最佳选择。

ABSTRACTOCE-0095534In this study, researchers at the University of Washington will determine the in-situ rates of gross and net primary productivity in the North Pacific Ocean using measurements of the isotopic composition and saturation level of dissolved oxygen. Marine productivity affects a wide range of fundamental properties of the earth from, for example, the concentration of CO2 and O2 in the atmosphere to the magnitude of potential fisheries harvests. Within the near future, potential climate change-induced alterations of ocean productivity could feedback into changes in the rate of anthropogenic CO2 build up in the atmosphere. All in all our ability to quantify rates of marine productivity is critical to our understanding of how earth's carbon cycle has changed in the past and will change in the future. Primary production (PP) rates in the ocean have historically been determined from rate measurements made in bottles. However, bottle measurements of PP suffer to an unknown extent from the inequality between in vitro and in situ conditions. Furthermore 14C uptake derived estimates of PP, by far the most common in vitro method, suffers an additional uncertainty about whether the rates represent gross or net PP. In a classic comparison, estimates of carbon export rates derived indirectly from subsurface estimates of oxygen utilization rates were twice the 14C-based measurements of primary production rates (Jenkins and Goldman, 1985). These uncertainties emphasize the need for PP rate determinations using methods that do not rely on bottle incubations. Recently a new technique has been developed to estimate both gross and net PP in the ocean (Luz and Barkan, 2000). It depends on extremely precise measurements of the isotopic composition of dissolved O2. The advantage of this method is that it does not require bottle incubations. In this study, the principal investigator will use this oxygen isotope method to determine in situ rates of gross and net PP in the N. Pacific and compare these rates to bottle measurements of PP made using 14C and 18O labeling techniques. The research team will make these measurements at two JGOFS time series sites in the subtropical (Station ALOHA) and subpolar (Ocean Station Papa) North Pacific. Both these sites have 10 or more years of 14C-based productivity data with which to compare in situ PP estimates determined by this new method. The time history of PP rate measurements at these two sites, the several estimates of carbon export made at these sites over the years (e.g., sediment traps, O2 budgets, DIC budgets, 234 Th budgets, etc.), and the contrast in biogeochemical regimes of these two sites (high vs. low nutrient) make the North Pacific an excellent choice for extending the application of the oxygen isotope method.