GLOBEC: Northeast Pacific Study: Mesoscale Zooplankton Distribution and Productivity

该项目涉及美国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化构成了对沿海地区浮游动物生物量、生产、分布、物种相互作用以及保留和损失的主要物理强迫。“主要研究者响应全球生物多样性委员会公告的具体内容，该公告呼吁：（a）三维中尺度调查，旨在确定浮游动物相对于其物理环境的分布和生产力;（B）过程研究，侧重于了解浮游动物原地种群动态过程以及物理和生物过程之间的相互作用。 目前尚不清楚加州海流系统中尺度特征如何影响浮游动物生物量、生产、分布或沿海地区的保留和损失。 这些相互作用的现象很少在加州附近进行研究，在俄勒冈州附近就更少了。 中尺度物理动力学相对容易测量，但需要高采样频率。 大多数测量浮游动物的标准方法根本不符合解决中尺度特征所需的采样频率。 GLOBEC要想取得成功，就必须应对这一根本挑战。 研究小组投入了十年时间，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生物量、分布和生产力。 他们发现，在加州北方海域的加州海流系统中，物理强迫和浮游动物生产力之间存在显著的中尺度相互作用。 在1993年的一项试点研究中，他们发现加州海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-但根本原因仍然不清楚。 GLOBEC NEP研究提供了一个无与伦比的机会，以了解这些动态上游-关闭俄勒冈州-因此，阐明基本过程。 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来研究物理和生物过程及其时空耦合。 他们将在中尺度调查中使用综合海洋-光学浮游生物计数器和ADCP，再加上临界网取样，以解决中尺度浮游动物大小和种类结构的时空分布问题。 与种群动态有关的比率将通过生物量光谱法（Zhou和亨特利，1997年）结合某些补充和独立的实地测量来确定。 该方法旨在对生物量和生产力进行估计-在与中尺度物理学相同的尺度上解决-并将澄清控制浮游动物生产力变化的因素。 这些结果不仅是至关重要的定义幼鲑（关键GLOBEC NEP目标物种）的“食物领域”，但可以提高我们的浮游动物种群和动态物理环境之间的相互作用的一般理解，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.