GLOBEC Northeast Pacific Study: Mesoscale Zooplankton Distribution and Productivity

该项目解决了美国GLOBEC东北太平洋研究的三个核心假设之一：“中尺度环流的时空变异性构成了对沿海地区浮游动物生物量、生产、分布、物种相互作用和留存与损失的主要物理强迫。”PIs对GLOBEC公告的具体部分作出回应，其中要求(A)进行三维中尺度调查，以确定浮游动物与其自然环境有关的分布和生产力，以及(B)过程研究，重点是了解浮游动物就地种群动态过程以及物理和生物过程之间的相互作用。目前尚不清楚加州当前系统的中尺度特征如何影响沿海地区的浮游动物生物量、生产、分布或留存和损失。这些相互作用的现象在加州很少被研究，在俄勒冈州更是很少。中尺度物理动力学相对容易测量，但需要较高的采样频率。大多数测量浮游动物的标准方法与解决中尺度特征所需的采样频率根本不兼容。GLOBEC必须应对这一根本性挑战才能取得成功。调查组花了十年时间开发和应用一种综合方法，以中尺度研究所需的高分辨率测量浮游动物的生物量、分布和生产力。他们发现，在加利福尼亚州北部附近的加州洋流系统中，物理强迫和浮游动物生产力之间存在着重要的中尺度相互作用。在1993年的一项初步研究中，他们发现加州洋流中心急流的生产力净下降，而邻近涡流系统的生产力净增加。物理生物过程的中尺度匹配是惊人的--但根本原因仍然不明。GLOBEC NEP的研究提供了一个无与伦比的机会，可以了解俄勒冈州上游的这些动态，从而阐明基本的过程。研究人员将通过测量和数学推导平流、垂直迁移和生产率的个别过程，研究物理和生物过程以及它们的时空耦合。他们将在中尺度调查中使用集成的海-空-光浮游生物计数器和ADCP，再加上关键的净采样，以解决中尺度上具有大小和物种结构的浮游动物的时空分布。与种群动态有关的速率将根据生物量光谱法(周和亨特利，1997年)结合某些补充和独立的实地测量来确定。该方法的目的是产生生物量和生产力的估计--与中尺度物理学解决的尺度相同--并将澄清控制浮游动物生产力变化的因素。这些结果不仅对确定幼鲑鱼(GLOBEC NEP的关键目标物种)的“食物领域”至关重要，而且还可以提高我们对浮游动物种群与其动态物理环境之间相互作用的一般理解，这是GLOBEC的中心目标。

This project addresses one of the three central hypotheses of the U.S. GLOBEC Northeast Pacific Study: "Spatial and temporal variability in mesoscale circulation constitutes the dominant physical forcing on zooplankton biomass, production, distribution, species interactions and retention and loss in coastal regions." The PIs respond to specific components of the GLOBEC announcement which call for (a) three dimensional mesoscale surveys aimed at determining the distribution and productivity of zooplankton in relation to their physical environment, and (b) process studies focused on understanding zooplankton in situ population dynamics processes and the interaction between physical and biological processes. It is not well understood how mesoscale features in the California Current System impact zooplankton biomass, production, distribution, or retention and loss from coastal regions. These interacting phenomena have been studied rarely off California, and even more rarely off Oregon. Mesoscale physical dynamics are relatively easy to measure, but require a high sampling frequency. Most standard methods of measuring zooplankton are simply not compatible with the sampling frequency required to resolve mesoscale features. This fundamental challenge must be met for GLOBEC to succeed. The group of investigators has invested a decade in the development and application of an integrated methodology for measuring zooplankton biomass, distribution and productivity at the high resolution required for mesoscale studies. They find significant mesoscale interactions between physical forcing and zooplankton productivity in the California Current System off northern California. In a 1993 pilot study, they found net decreasing productivity in the central jet of the California Current, and net increasing productivity in adjacent eddy systems. The mesoscale match of physical biological processes was striking - but underlying causes remain obscure. The GLOBEC NEP study offers an unparalleled opportunity to understand these dynamics upstream - off Oregon - and so to shed light on fundamental processes. The investigators will study both physical and biological processes, and their spatio-temporal coupling, by measuring and mathematically deducing individual processes of advection, vertical migration, and rates of productivity. They will use the integrated Sea-Soar-Optical Plankton Counter and ADCP in mesoscale surveys, coupled with critical net sampling, to resolve spatial and temporal distributions of size- and species-structured zooplankton at the mesoscale. Rates pertinent to population dynamics will be determined from the biomass spectral method (Zhou and Huntley, 1997) in conjunction with certain complementary and independent field measurements. The approach is aimed at producing estimations of biomass and productivity - resolved at the same scale as mesoscale physics - and will clarify factors controlling variations in zooplankton productivity. These results are not only critical to defining the "food field" of juvenile salmon (a key GLOBEC NEP target species), but can improve our general understanding of interactions between zooplankton populations and their dynamic physical environment, with is the central goal of GLOBEC.