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

有机壁鞭毛藻囊是分类学上定义明确的干酪根颗粒，在早期成岩有氧降解的易感性方面表现出很大的物种特异性差异。作为具有不同稳定性的有机颗粒的代表，这使得它们对研究颗粒有机物的降解过程非常有用。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，因此获得有关退化过程及其控制因素的信息至关重要。在这项研究中，我们的目标是通过量化物种特定的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/或化学特征。这些信息可以形成一种方法的基础，用于量化沉积档案中过去的底部/孔隙水氧浓度。除此之外，我们还将研究囊状降解是否受到周围沉积环境中不同不稳定性有机质的数量和组成的差异的影响。为此，我们将在实验室和受控氧化还原条件下以及在岩心研究中研究鞭毛藻囊的降解过程。在实验室实验中，已知囊肿成分的沉积物将在缺氧和缺氧条件下孵育。这些实验的材料来自两个具有缺氧底水的高生产力地区（阿拉伯海东部，西北非洲）和两个低生产力地区(地中海中东部发现盆地盐水（缺氧）和盆地边缘沉积物（缺氧）。在现场实验中，来自阿拉伯海氧最低带的高压蒸压沉积物具有已知的囊肿成分，已被分割并转移到由透析膜（微生物紧密但可扩散氧气）和孔径为5 μ m（微生物和氧气都能穿透）的聚碳酸酯膜组成的袋中。这些材料已经暴露在含氧、缺氧和低氧的自然环境中5年，在不同的水体中，氧竞争是已知的或监测到的。从2008年到2013年，这些沉积物的等量每年收获一次。为了确定孔隙水中氧浓度与地下沉积物中鞭毛藻囊肿降解率之间的关系，将把地中海东部发现盆地盐水系统和阿拉伯海及西北非洲海域的氧气最低带的多核沉积物中囊肿浓度和组合组成的下核变化与孔隙水中已知的氧浓度进行比较。在此基础上，研究了发现盆地多岩心和重岩心下向和上向氧化锋相关的孔隙水氧梯度的降解过程。

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.