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，迄今为止进行的大多数船上和现场工作都涉及添加比环境水平高一到两个数量级的限制性营养物质，导致大量繁殖，这在所调查的自然生态系统中通常不会观察到。因此，有必要了解实际浓度下连续铁和养分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化学调节系统在南大洋进行这种类型的实验。该系统以连续的流量模拟真实的垂直平流过程，将铁和营养物质以自然水平输送到孵化的船上实验中。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水中铁浓度的变化；(2)一定铁浓度下上升流速率的变化对群落结构有何影响？(3)铁化学形态如何影响浮游植物群落组成？(4)铁供应的变化将如何影响生物硫的生产？

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?