Structure and Dynamics of Plankton Communities in the Antarctic Frontal Zone: Interactions of Physical Forcing, Iron Limitation and Microzooplankton Grazing

这个研究项目是美国联合全球海洋通量研究（JGOFS）南大洋项目的一部分，旨在：(1)更好地了解南大洋有机和无机碳通量，(2)确定调节这些通量的大小和变化的物理、生态和生物地球化学有利条件和过程，以及(3)将这些通量置于当代全球碳循环的背景下。南大洋是一个巨大而多变的环境，在全球碳循环中可能扮演着重要角色。JGOFS南大洋项目旨在通过调查罗斯海大陆架和南极极锋区这两个重要子系统的季节和空间动态来推进对该地区的了解。该项目将通过确定微生物群落结构、评估浮游植物生长速率和浮游微动物放牧率，在开放海洋锋面区进行四次巡游，覆盖春季、夏季和秋季。本研究的总体目标是了解物理过程（平流、混合和光照）、铁限制和放牧如何相互作用，以决定开放海洋中浮游生物群落的结构和生产。浮游生物群落的种群丰度和生物量将通过分析流式细胞术（细菌和浮游植物）和显微镜（纳米和微型浮游生物）进行评估，以确定它们相对于极地锋的物理特征的时空格局。浮游植物和细菌的生长速度，以及微型浮游动物食草动物和细菌的生长速度将通过一套补充方法进行测量，包括稀释、荧光标记猎物、大小分选和细菌的溶酶测定。该项目的研究结果将有助于全面了解世界海洋高营养、低叶绿素区域浮游植物的控制机制和营养相互作用。它们还将有助于确定潜在的全球变化如何影响水柱的稳定性，以及南大洋的物理作用力如何改变食物网结构、碳储存和从光带出口。

96-34053 Landry This research project is part of the US Joint Global Ocean Flux Study (JGOFS) Southern Ocean Program aimed at (1 ) a better understanding of the fluxes of carbon, both organic and inorganic, in the Southern Ocean, (2) identifying the physical, ecological and biogeochemical favors and processes which regulate the magnitude and variability of these fluxes, and (3) placing these fluxes into the context of the contemporary global carbon cycle. The Southern Ocean is a vast and variable environment with a potentially large role in global carbon cycling. The JGOFS Southern Ocean Program seeks to advance the understanding of this region by investigating seasonal and spatial dynamics in two important subsystems -- the Ross Sea shelf and the Antarctic Polar Front Zone. This project will contribute to this effort by determining microbial community structure and by assessing rates of phytoplankton growth and microzooplankton grazing on four cruises covering the spring, summer, and autumn seasons in the open-ocean frontal zone. The overall goal of this research is to understand how physical processes (advection, mixing, and light), iron-limitation, and grazing interact to determine plankton community structure and production in the open oceans. Population abundances and biomasses of the plankton community will be assessed by analytical flow cytometry (bacteria and phytoplankton) and microscopy (nano- and microplankton) to determine their temporal and spatial patterns relative to physical features of the polar front. Growth rates of phytoplankton and bacteria, and microzooplankton herbivory and bacterivory will be measured with a suite of complementary methods including dilution, fluorescently labeled prey, size fractionation, and a Iysozme assay for bacterivory. Results of this project will contribute to the general understanding of phytoplankton control mechanisms and trophic interactions in high-nutrient, low-chlorophyll regions of the world's ocea ns. They will also help to identify how potential global change affects water-column stability and how physical forcing in the Southern Ocean may alter food web structure, carbon storage and export from the euphotic zone.