Physico-chemical and microbial processes governing the decay of organic substance in sediment under anoxic conditions

缺氧条件下控制沉积物中有机物质腐烂的物理化学和微生物过程

• 批准号: 396708702
• 负责人: Professor Dr. Christian Gerhard Ballhaus
• 金额: --
• 依托单位: Abteilung Paläontologie
• 依托单位国家: 德国
• 项目类别: Research Units
• 财政年份: 2018
• 资助国家: 德国
• 起止时间: 2017-12-31 至 2020-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/396708702?language=en
• 关键词: Physico; chemical; microbial; processes; governing

To fossilize soft tissue of marine taxa it is essential that a carcass be transferred rapidly to anoxic conditions and isolated from potential scavengers. A practical way to achieve this is by burying a decaying carcass or a living sessile species in sediment. The oxidation of organic carbon to HCO3- and CO32- within the sediment will reduce the major electron acceptors in sediment and seawater, i.e. ferric iron and sulfate. The decay reactions will create local Eh and pH haloes around a carcass within which FeS sulfide, siderite, and other carbonate phases may be stabilized. These phases may then replace or template organic tissue, or encase the organic material in concretions. Within the research unit FOR 2685 the applicant will develop experimental routines that allow to investigate in-situ the anoxic decay of fish and echinoderms within a marine sediment. The major aim is to quantify the rates by which replacement can take place. While an experiment is progressing, organic material will be sampled from time to time. Inorganic precipitates will be identified by Raman spectroscopy. Bacterial communities emerging will be characterised in close collaboration with members of the research unit. It is expected that the templation by inorganic material - FeS phases, siderite, calcite - may be a matter of weeks to months. The characterisation of bacterial communities, an important aspect in the present proposal, will elucidate if pseudomorphic replacement reaction are inorganic by nature and driven only by pH and Eh gradients, or if they must be mediated by bacteria in order to be efficient.

为了使海洋类群的软组织化石化，必须将尸体迅速转移到缺氧条件下并与潜在的食腐动物隔离。实现这一目标的一个实用方法是将腐烂的尸体或活的固着物种埋在沉积物中。沉积物中有机碳氧化成HCO3-和CO32-会减少沉积物和海水中的主要电子受体，即三价铁和硫酸盐。衰变反应将在尸体周围产生局部 Eh 和 pH 晕，其中 FeS 硫化物、菱铁矿和其他碳酸盐相可以稳定在其中。然后，这些相可以取代或模板有机组织，或将有机材料包裹在结核中。在 FOR 2685 研究单位内，申请人将开发实验程序，以调查海洋沉积物中鱼类和棘皮动物的原位缺氧腐烂情况。主要目标是量化更换率。在实验进行过程中，会不时对有机材料进行采样。无机沉淀物将通过拉曼光谱来鉴定。新兴细菌群落的特征将与研究单位成员密切合作。预计无机材料（FeS相、菱铁矿、方解石）的模板化可能需要几周到几个月的时间。细菌群落的表征是本提案的一个重要方面，它将阐明假晶置换反应本质上是无机的并且仅由 pH 和 Eh 梯度驱动，还是必须由细菌介导才能有效。