Untersuchung der Fraktionierung von Stickstoffisotopen in marinen Sedimenten, abhängig von unterschiedlichen Sedimentcharakteristika

活性氮被大规模带入海洋，导致沿海海洋富营养化。在提高初级产量的同时，它也影响了全球的碳循环。鉴于这些增加的投入和对海洋氮预算的持续修订，概述的研究项目将提供工具，以便更好地估计海洋中的氮汇。具体地说，我们的目标是测量沉积反硝化和厌氧氨氧化(厌氧氨氧化)过程中稳定的氮同位素分馏，我们预计这些分馏比之前假设的更具变异性。重点研究了生物灌溉的影响和不同底泥氧化还原条件对两种脱氮过程中同位素分馏的影响。在沉积物培养期间，应分析孔隙水的浓度和不同氮物种的同位素组成，这些氮物种是由各自的微生物隔离或产生的。由于氧化还原状态、人为氮或碳负荷以及底层水的氧饱和度具有很高的自然变异性，波罗的海/北海过渡为同位素效应的变化提供了一个很好的研究区域。这可在以后用作改进陆架沉积物脱氮量估算的建模方法的基础。

Reactive nitrogen is entrained to the ocean at large scales, leading to eutrophication of coastal oceans. As this enhances primary production, it also affects global carbon cycling. In the light of these increased inputs and an ongoing revision of the marine nitrogen budget, the outlined research project shall provide tools for a better estimation of nitrogen sinks in the ocean. Specifically, we aim to measure stable nitrogen isotope fractionation during sedimentary denitrification and anammox (anaerobic ammonia oxidation), which we expect to be more variable than previously assumed. The focus is set on the influence of bioirrigation and the influence of varying sediment redox conditions on the isotope fractionation of both nitrogen removal processes. During sediment incubations, the porewater shall be analysed for concentrations and isotopic composition of different nitrogen species that are sequestered or produced by the respective micro-organisms. Because of the high natural variability regarding redox state, anthropogenic nitrogen or carbon loads and oxygen saturation in bottom waters, the Baltic/North Sea transition provides an excellent study area for the variances in isotope effects. This can later be used as a basis for modelling approaches to improve the estimation of nitrogen removal by shelf sediments.