Collaborative Research: Assessing the Genetic Potential andPhysiological Controls of N2 Fixation in a N-Limited Estuary

小行星9615772 河口的生产力通常由氮（N）的可用性控制，即使大气中有大量的气态N2。N2固定，即大气中的N2转化为细胞中的氮，由于N2固定蓝藻的密集繁殖，可以在淡水生态系统的浮游生物中以高速率发生。这些水华可能是有毒的，并导致水的味道和气味问题。这样的花很少 在 海洋 系统， 甚至 那些 正在经历富营养化（由于增加了 营养素输入）。 之间的对比 淡水中固氮生物占优势，而河口和海洋中固氮生物明显缺乏，这为拟议的研究提供了基础。 河口定义了从淡水到海洋的过渡 环境， 并且因此提供 一 基础 研究控制淡水和海洋环境中固氮水华的因素。本研究的目的是确定如何固氮生物的空间和时间分布在淡水，中盐和真盐河段的纽斯河口。 在这个研究项目中开发的概念框架将提供一个新的视角，了解在海洋，河口和淡水环境中的固氮潜力，这将有助于了解何时何地固氮水华可能发生在文化富营养化的威胁。这项调查的一个特别新颖的方面是，实验操作将用于确定盐度和营养物质如何影响特定的N2固定人口的分布，生长和活动，使用分子生物学方法。这些实验的结果将为河口、淡水和海洋环境中生产力和藻华形成的调节提供新的信息。

9615772 Paerl Productivity in estuaries is often controlled by nitrogen(N) availability,even though there is a vast reservoir of gaseous N2 in the atmosphere. N2 fixation, the conversion of atmospheric N2 into cellular nitrogen, can occur at high rates in the plankton of freshwater ecosystems, due to dense blooms of N2 fixing cyanobacteria. These blooms can be toxic and cause water taste and odor problems. Such blooms are scarce in marine systems, even those undergoing eutrophication (becoming more productive as a result of increased nutrient inputs). The contrast between the predominance of N2 fixing organisms in freshwater and the apparent dearth of N2 fixing organisms in estuaries and oceans, provides the basis for the proposed research. Estuaries define the transition from freshwater to the marine environment, and thus provide a basis for investigating the factors that control N2 fixing blooms in both freshwater and marine environments. This objective of this research is to define how N2 fixing organisms are distributed spatially and temporally in the freshwater, mesohaline and euhaline reaches of the Neuse River estuary. The conceptual framework developed in this research project will provide a new perspective for understanding N2 fixation potentials in marine, estuarine and freshwater environments, which will help to understand when and where nitrogen-fixing blooms are likely to occur in response to the threat of cultural eutrophication. A particularly novel aspect of this investigation is that experimental manipulations will be used to determine how salinity and nutrients affect the distribution, growth and activity of specific N2 fixing populations using a molecular biology approach. The results of these experiments will provide new information on the regulation of productivity and algal bloom-formation in estuaries, freshwaters, and the marine environment.