Salinity Effects on Nitrogen Dynamics in Shallow, Coastal Sediments

摘要：在这项研究中，德克萨斯大学奥斯汀分校的研究人员希望能够进一步了解沿海生态系统中生物相关氮化合物在盐度范围内的浓度、形式、转化率和命运的控制机制。 氮通常限制沿海地区的初级生产。 浅水沉积物是海岸带生态系统中氮转化和去向的主要生物地球化学场所。上层沉积物提供了有利于微生物氮循环转化的环境，包括有机氮矿化、硝化（亚硝酸盐和硝酸盐）、反硝化和异化硝酸盐还原为铵（DNRA），但每个过程的重要性随盐度和其他因素而变化。 最近的证据表明，反硝化作用等关键过程的传统范例可能不适用于所有沉积物系统。 本调查的目的是比较和联合收割机化学，同位素和分子生物学方法来定义在沿海系统的盐度梯度的N转化机制。 具体的假设是：1。盐度和有效有机质通过影响硫化物浓度来控制再生氮的去向. N2O的释放和DNRA的重要性，相对于N2的生产，减少sediments.The实验盐度增加，预计将产生相关的国际关注的问题，包括沿海富营养化，有害藻华，淡水供应和全球变化的信息。 他们将通过将分子生物学技术与化学和稳定同位素方法相结合来推动海洋方法的发展，以澄清参与氮转化的细菌的结构和功能。 将为少数民族院校的学生和高中师生提供机会，让他们参加关于沿海环境的实地研究，了解营养物质和盐度对沿海生态系统进程的重要性。

ABSTRACTOCE- 0350651In this study, researchers at the University of Texas at Austin hope to advance our understanding of the mechanisms controlling the concentrations, forms, transformation rates, and fate of biologically relevant nitrogen compounds over a range of salinities in coastal ecosystems. Nitrogen often limits primary production in coastal regions. Shallow water sediments are primary biogeochemical sites regulating the transformation and fate of N in coastal ecosystems. Upper sediment layers provide environments conducive to microbial N cycle transformations, including organic N mineralization, nitrification (to nitrite and nitrate), denitrification, and dissimilatory nitrate reduction to ammonium (DNRA), but the importance of each process varies with salinity and other factors. Recent evidence indicates that traditional paradigms of key processes, such as denitrification, may not be accurate or complete for all sediment systems. The objectives of this investigation are to compare and combine chemical, isotopic, and molecular biology methods to define N transformation mechanisms in coastal systems over a salinity gradient. Specific hypotheses to be examined are:1. Salinity and available organic matter control the fate of regenerated N by affecting sulfide concentrations in shallow coastal ecosystems.2. The importance of N2O release and DNRA, relative to N2 production, increases with salinity in reduced sediments.The experiments are expected to yield information relevant to issues of international concern including coastal eutrophication, harmful algal blooms, freshwater supply, and global change. They will advance marine methodological development by combining molecular biology techniques with chemical and stable isotopic approaches to clarify the structure and function of bacteria involved in N transformations. Opportunities will be provided for minority institution students and high school teachers and students to participate in field research on coastal environments and learn about the importance of nutrients and salinity to coastal ecosystem processes.