Collaborative Research: Continuous Nutrient Input Effects on Algal Community Structure using Shipboard Chemostats

营养物和铁添加实验是一种基本的海洋学工具，它使我们在控制海洋生产力和碳循环方面的知识取得了重大进展。 然而，迄今为止进行的船上和现场工作大多涉及添加比环境水平高出一至两个数量级的限制性营养素，导致在所调查的自然生态系统中通常观察不到的大规模水华。 因此，有必要了解铁和营养盐在实际浓度下持续输入对浮游植物群落结构和海洋碳循环的影响。 来自特拉华州大学和查尔斯顿大学的主要研究人员将利用他们的自然群落恒化器系统在南大洋进行这类实验。 该系统以自然水平提供铁和营养素，以连续的流速模拟真实世界的垂直平流过程。 本研究的具体目标是解决以下四个问题：（1）浮游植物的种类组成如何响应上升流水中铁浓度的变化？(2)在一定的铁浓度下，上升流速率的变化对群落结构有什么影响？(3)铁的化学形态如何影响浮游植物群落的组成？以及（4）变化的铁供应将如何影响生物硫的产生？

Nutrient and iron addition experiments are a basic oceanographic tool that has resulted in major advances in our knowledge of controls on oceanic productivity and carbon cycling. However, most of the shipboard and in-situ work carried out to date has involved additions of limiting nutrients that are one to two orders higher than ambient levels, resulting in massive blooms that are not typically observed in the natural ecosystems being investigated. For this reason, it is necessary to understand the consequences of continuous iron and nutrient inputs at realistic concentrations on phytoplankton community structure and oceanic carbon cycling. The principal investigators from the University of Delaware and the University of Charleston will carry out this type of experiment in the Southern Ocean utilizing their natural community chemostat system. This system delivers iron and nutrients at natural levels to incubated shipboard experiments at continuous flow rates that simulate real-world vertical advection processes. The specific goals of the proposed research is to address the following four questions: (1) How does phytoplankton species composition respond to changes in iron concentrations in upwelled water?; (2) What effect will variability in upwelling rates at a give iron concentration have on community structure?; (3) How does iron chemical speciation affect the composition of phytoplankton communities?; and (4) How will a changing iron supply affect the production of biogenic sulfur?