Quantification and characterisation of the aerobic degradation of organic-walled dinoflagellate cysts

有机有壁甲藻包囊是分类上定义明确的干酪根颗粒，在早期成岩好氧降解的脆弱性方面显示出物种特有的巨大差异。作为具有差异性的有机质颗粒的代表，这为研究颗粒状有机物的降解过程提供了有利条件。由于它们在工业界和学术界都被用作重建古环境、古海洋学和确定海洋档案地层学的工具，因此必须获得关于退化过程及其控制因素的信息。在这项研究中，我们旨在通过量化物种特定降解率与氧浓度的关系来扩大这一信息，并确定降解过程的生物(微生物)和/或化学性质。这一信息可以作为量化沉积档案中过去底水/孔隙水氧浓度的方法的基础。除此之外，我们还将调查包囊降解是否受到周围沉积环境中具有差异的有机质的数量和组成的差异的影响。为此，我们将在实验室和野外实验中，在受控氧化还原条件下以及在下层研究中研究甲藻孢囊的降解过程。在实验室实验中，具有已知包囊成分的沉积物将在有氧和缺氧条件下孵化。这些实验的材料来自两个底部水域缺氧的高生产力地区(阿拉伯海东部，非洲西北部)和两个低生产力地区(地中海中部发现盆地卤水(缺氧)和盆地边缘的沉积物(氧气)。在现场实验中，来自阿拉伯海氧气最小区的已知包囊成分的高压灭菌沉积物被分割并转移到由透析膜(微生物紧密但可扩散氧气)和聚碳酸酯凝视器组成的袋子中，孔径为5MU-m(微生物和氧气的穿透性)。该材料在已知或监测到含氧量的不同水团中暴露在有氧、亚氧和低氧的自然环境中已有五年。从2008年到2013年，每年都会采集一次这些沉积物的等量。为了确定地下沉积物中孔隙水含氧量与甲藻孢囊降解速率之间的关系，将东地中海发现盆地卤水系统以及阿拉伯海和非洲西北部海域最低含氧区的多岩心沉积物中孢子体浓度和组合成分的下部岩心变化与已知的孔隙水含氧量进行比较。此外，还将沿着与发现盆地地区多个和重力岩心的氧化前锋向下和向上移动有关的孔隙水氧梯度来研究降解。

Organic walled dinoflagellate cysts are taxonomically well defined kerogen particles that show large species specific variation in their vulnerability to early diagenetic aerobic degradation. As representative of organic matter particles with differential lability, this makes them useful to study particulate organic matter degradation processes. As they are used both in industry and in academia as tools to reconstruct palaeoenvironment, palaeoceanography and determine the stratigraphy of marine archives it is essential to gain information about the process of degradation and its controlling factors. In this study we aim to enlarge this information by quantifying the species specific degradation rates in relationship with oxygen concentrations and to determine the biologic (microbial) and/or chemical character of the degradation process. This information can form the basis for a method to quantify past bottom/pore water oxygen concentrations from sedimentary archives. Apart from this we will investigate if cyst degradation is influenced by differences in the amount and composition of organic matter of differential lability in the ambient sedimentary environment. For this we will study the degradation process of the dinoflagellate cysts in a laboratory and field experiments under controlled redox conditions as well as in downcore studies. In the laboratory experiment, sediments with a known cysts composition will be incubated under oxic and anoxic conditions. Material for these experiments is derived from two high productivity regime sites with anoxic bottom waters (eastern Arabian Sea, off NW Africa) and two low productivity regime sites (central eastern Mediterranean discovery basin brine (anoxic) and sediments of the basin margin (oxic). In the field experiment, autoclaved sediments from the Arabian sea oxygen minimum zone with a known cyst composition have been partitioned and transferred to bags composed of dialysis membrane (microbe tight but diffusible for oxygen) and polycarbonate gaze with a pore size of 5 mu-m (penetration of both microbes and oxygen). The material has been exposed to oxic, suboxic and hypoxic natural environments for five years in different water masses of which the oxygen contend is known or monitored. Aliquots of these sediments have been harvested once a year from 2008 to 2013. For determination of the relationship between pore water oxygen concentrations and degradation rates of dinoflagellate cysts in subsurface sediments, the downcore alteration in cyst concentration and association composition in multicore sediments from the Eastern Mediterranean Discovery Basin brine system and the oxygen minimum zones of the Arabian Sea and off NW Africa will be compared to already known oxygen concentrations in pore waters. Furthermore the degradation will be studies along pore water oxygen gradients related to downward and upward moving oxidation fronts in multi and gravity cores of the Discovery Basin region.