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

9615771卡彭河口的生产力通常受氮(N)可用性的控制，即使大气中有大量的气态氮气。由于固氮蓝藻的密集繁殖，在淡水生态系统的浮游生物中，大气中N2转化为细胞氮的固定作用可以以很高的速率发生。这些花是有毒的，会导致水的味道和气味问题。这种水华在海洋系统中很少见，即使是那些正在富营养化的系统（由于营养投入增加而变得更有生产力）。淡水中固氮生物的优势与河口和海洋中固氮生物的明显缺乏之间的对比，为提出的研究提供了依据。河口定义了淡水环境向海洋环境的过渡，从而为研究淡水和海洋环境中控制N2固定华的因素提供了基础。本研究的目的是确定新use河河口淡水、中盐和真盐河段固氮生物的时空分布。本研究项目建立的概念框架将为理解海洋、河口和淡水环境中的氮固定潜力提供一个新的视角，这将有助于了解在应对文化富营养化威胁的情况下，固氮华可能在何时何地发生。这项研究的一个特别新颖的方面是，实验操作将使用分子生物学方法来确定盐度和营养物质如何影响特定N2固定种群的分布、生长和活性。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。

9615771 Capone 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.