RedoxFlux: Biogeochemical fluxes and transformations at pelagic redoxclines in lakes

氧化和缺氧水体之间的界面，即氧化还原跃层，分隔或连接着两个截然不同的生境，是许多湖泊生物地球化学转化的热点。在氧化还原跃层深处，发生了硫、铁和锰的强烈循环。这种循环涉及化学反应和微生物反应，相应的转化速率主要受(I)溶解物质和颗粒物质的垂直运输、(Ii)反应和沉淀-溶解动力学以及(Iii)光的可用性控制。在这个项目中，我们将对这些过程的相互作用有一个基于过程的理解。将在三个不同湖泊的野外实验中估计垂直通量和生物地球化学周转率，这三个湖泊代表了三个不同的水体，在减少化学物种、光照和垂直混合方面的有效性。基础化学反应和微生物反应的详细动力学将在实验室中的中观实验中进行研究，该实验为其中两个研究地点设立。在一种创新的方法中，中温带将独立地模拟密度分层、所有相关成分的垂直通量和垂直混合。实验室和现场实验的结果将被合并到一个基于过程的数值模型中，允许将我们的结果转移到不同的水生系统和不断变化的环境条件。

The interface between oxic and anoxic water bodies, the redoxcline, separates, or rather connects two very contrasting habitats and is a hotspot of biogeochemical transformations in many lakes. At the depth of the redoxcline, intense cycling of, e.g. sulfur, iron and manganese, occurs. This cycling involves chemical as well as microbial reactions and the corresponding transformation rates are mainly controlled by (i) vertical transport of dissolved and particulate substances, (ii) reaction and precipitation-dissolution kinetics, and (iii) by the availability of light. In this project we will gain a process-based understanding of the interplay of these processes. Vertical fluxes and biogeochemical turnover rates will be estimated in field experiments at three different lakes, representing three contrasting water bodies in terms of the availability of reduced chemical species, light, and vertical mixing. The detailed kinetics of the underlying chemical and microbial reactions will be studied in laboratory mesocosm experiments, set up for two of the study sites. In an innovative approach, the mesocosms will independently mimic density stratification, vertical fluxes of all relevant constituents and vertical mixing. Results from laboratory and field experiments will be combined into a process-based numerical model, allowing for a transfer of our results to different aquatic systems and to changing environmental conditions.