Coordination Funds

地下河口是内陆含水层和公海之间隐藏的连接带，在这里大气淡水和循环海水混合并发生重大的生物地球化学变化。因此，它们被认为是影响海洋元素净通量的强大生物地球化学反应器。DynaDeep的动机是我们需要了解地下河口海洋-陆地相互作用的范围和功能，以便了解沉积陆海界面内生态系统功能的当前动态和未来轨迹。特别是，水文和形态动力学对地下流动和运输的影响尚不清楚，对生物地球化学反应和微生物栖息地特征的相关影响尚未研究。我们提出在高能海滩的深层地下存在一个迄今尚未开发的生物地球化学反应器，其中动态边界条件传播到地下数十米，导致地球化学条件的强烈时空变异性。因此，高能海滩下的地下河口可能形成一个独特的栖息地，与其他通常更稳定的地下环境不同，这里有适应的微生物群落。DynaDeep将研究地下水流动模式作为水动力学和形态动力学的函数。它将提供有机物的生物和非生物转化速率，并研究相关的氧化还原过程。此外，它将评估微量金属和金属同位素的转化和分馏。微生物与有机物的相互作用将被研究，以及微生物群落的多样性和代谢功能。六个次级项目将在联合实地运动、共享抽样方法和实验工作方面进行合作，并在综合方法中使用数学模型。在第一阶段，子项目将在Spiekeroog岛共同建立一个地下河口在线观测站，详细调查一个核心站点，然后在第二阶段验证其他高能站点的观测结果。最终，DynaDeep将阐明高能海滩深层动态地下与沿海生态系统以及碳、营养和微量元素循环的全球相关性。

Subterranean estuaries are hidden connective zones between inland aquifers and the open sea where meteoric freshwater and circulating seawater mix and undergo major biogeochemical changes. Hence, they are considered powerful biogeochemical reactors affecting elemental net fluxes to the sea. DynaDeep is motivated by the fact that we need to understand the extent and functionality of marine-terrestrial interactions in subterranean estuaries, in order to comprehend the current dynamics and future trajectory of ecosystem functioning within the sedimentary land-sea interface. In particular, the effect of hydro- and morphodynamics on subsurface flow and transport is unclear and related consequences on biogeochemical reactions and microbial habitat characteristics have not been investigated. We propose the existence of a so far unexplored biogeochemical reactor within the deep subsurface of high-energy beaches, where dynamic boundary conditions propagate tens of meters into the subsurface leading to strong spatio-temporal variability of geochemical conditions. Subterranean estuaries below high-energy beaches may thus form a unique habitat with an adapted microbial community unlike other typically more stable subsurface environments. DynaDeep will study groundwater flow patterns as a function of hydro- and morphodynamics. It will deliver rates of biotic and abiotic transformation of organic matter and investigate related redox processes. Furthermore, it will assess transformation and fractionation of trace metals and metal isotopes. Microbial interactions with organic matter will be investigated, as well as the diversity and metabolic functioning of microbial communities. Six subprojects will cooperate in joint field campaigns, shared sampling approaches as well as experimental work and use mathematical models in an integrative approach. In the first phase, the subprojects will jointly establish a Subterranean Estuary Online Observatory on the island of Spiekeroog to investigate one core site in detail, before verifying observations at other high-energy sites in a second phase. Ultimately, DynaDeep will elucidate the global relevance of the dynamic deep subsurface of high-energy beaches for coastal ecosystems as well as for carbon, nutrient and trace element cycling.