Sulphate reduction and anaerobic methane oxidation in sediments of Lake Grevelingen

在季节性分层和缺氧的沿海盐湖Grevelingen，人为增加的养分投入已经支持了几十年的高初级产量。这导致了沉积物中大量有机物的积累。由于大多数氧气已经在沉积物的上部毫米中丢失，因此大多数有机物目前在缺氧条件下通过硫酸盐还原（SR）和甲烷生成而降解。硫酸盐还原在硫酸盐-甲烷过渡区（SMTZ）通过厌氧氧化去除向上扩散的甲烷中也起着关键作用。甲烷的不完全氧化导致甲烷剖面向上倾斜，SMTZ变宽，在较宽的深度范围内同时存在硫酸盐和甲烷。在其他系统的沉积物中也观察到造成如此广泛的SMTZ的过程，但仍未完全了解。在这里，我们将扩展现有的孔隙水数据集，利用SR和甲烷厌氧氧化（AOM）的速率测量来扩展Grevelingen湖沉积物中硫酸盐和甲烷的动态，以进一步了解这两个过程在SMTZ中的分布和程度。此外，还将研究铁、锰和磷的沉积动力学以及AOM对其源汇行为的影响。该研究将有助于更好地理解海洋沉积物中甲烷厌氧氧化的过程及其对其他生物地球化学循环的影响。

In seasonally stratified and hypoxic coastal saline Lake Grevelingen anthropogenically enhanced nutrient input has supported a high primary production already for several decades. This has resulted in the accumulation of large amounts of organic matter in the sediments. Because most oxygen is already lost in the upper millimetres of the sediment, most of this organic matter is currently degraded under anoxic conditions by sulphate reduction (SR) and methanogenesis. Sulphate reduction also plays a key role in removing upward diffusing methane through anaerobic oxidation in the sulphate-methane-transition zone (SMTZ). Incomplete oxidation of methane leads to an upward tailing of the methane profile and a broadening of the SMTZ with both sulphate and methane being present over a wide depth interval. The processes responsible for such a broad SMTZ, which is also observed in sediments of other systems, are still incompletely understood. Here, we will expand the existing pore water data set on sulphate and methane dynamics in sediments of Lake Grevelingen with rate measurements of SR and anerobic oxidation of methane (AOM) to obtain further insight into the distribution and extent of both processes in the SMTZ. Furthermore, the sedimentary dynamics of iron, manganese and phosphorus and the impact of AOM on their source and sink behaviour will be studied. This study will contribute to a better understanding of the processes leading to anaerobic oxidation of methane in marine sediments and the impact on other biogeochemical cycles.