Collaborative Research: RUI -- Response of Nitrifying Bacteria to Fluctuating Hypoxia in Estuarine and Marine Sediments

硝化作用有助于去除生态系统中的固定氮；它是调节生态系统生产力和全球氮收支的重要过程。在缺氧的河口，硝化作用受到损害，减少了固定氮的去除。底水缺氧导致孔隙水中HS-浓度增加，从而延长对好氧硝化细菌的抑制作用。西佛罗里达大学的一名研究人员认为，在长达一周的缺氧事件中，硝化活性的丧失将降低反硝化速率，尽管厌氧NH4+氧化（厌氧氨氧化）的N2产量可能会增加。在这项研究中，来自西佛罗里达大学的科学家将调查好氧硝化菌的群落组成在不同的氧张力下是如何不同的。还将考虑硝化菌对短期缺氧事件的反应，以及缺氧程度和底水NO3-浓度（通过反硝化或厌氧氨氧化）如何影响N2水平。最后，由于硝化群落对周期性缺氧和HS-暴露的适应具有重要的生态意义，研究人员将研究硝化菌对持续数小时至数天的间歇性缺氧的适应程度，特别是当暴露于HS-时间歇性缺氧。如果社区适应并成为HS耐受性，那么他们可以在条件有利时进行硝化，而不会延长滞后期。因此，在这些系统中，通过反硝化去除氮将更有效。此外，厌氧氨氧化在河口环境中的作用还没有得到很好的研究，特别是它对河口氮收支的贡献。如果厌氧氨氧化率显著，它将建议对河口固定氮去除过程进行重大修订。

ABSTRACTOCE- 0352221 / OCE- 0352216 Nitrification contributes to removing fixed nitrogen from ecosystems; it is a centrally important process modulating ecosystem productivity and the global nitrogen budget. In anoxic estuaries, nitrification is compromised, reducing the removal of fixed nitrogen. Bottom water anoxia leads to increased HS- concentrations in pore waters that can lead to extended inhibition of aerobic nitrifying bacteria. A researcher at the University of West Florida believes that the loss of nitrification activity during weeklong hypoxic events will reduce denitrification rates, although N2 production by anaerobic NH4+ oxidation (anammox) may be enhanced. In this study, the scientist from the University of West Florida will investigate how the community composition of aerobic nitrifiers differs under varying oxygen tensions. How the nitrifiers respond to short-term hypoxic events will also be considered, as well as how the degree of hypoxia and bottom water NO3- concentrations (either through denitrification or anammox) will affect N2 levels. And, finally, because adaptation by the nitrifying community to periodic hypoxia and HS- exposure has important ecological implications, the researcher will investigate the degree to which nitrifiers can adapt to intermittent hypoxia lasting hours to days, specifically when intermitted with exposure to HS-. If communities adapt to and become HS- tolerant, then they can nitrify when conditions are favorable without extended lag periods. Thus, nitrogen removal through denitrification would be more efficient in these systems. In addition, the role of anammox in estuarine environments is not well studied, particularly its contribution to estuarine nitrogen budgets. If anammox rates are significant, it will suggest a major revision of the fixed nitrogen removal processes in estuaries.