Redox-driven biogeochemical element cycles play a central role in converting organic matter in aquatic ecosystems. They also perform key functions such as removing nitrate, mitigating the formation of greenhouse gases and weakening the effects of contaminants. Recent research has revealed the presence of redox-active compounds in these ecosystems with hitherto unknown redox properties. These substances are metastable (that is, non-equilibrium solid phases), which can both donate and accept electrons. They are highly redox reactive and recyclable and may act as biogeobatteries by temporarily storing electrons. Their lifetime, however, is limited, and with time they become more crystalline and less reactive. In this Review, we argue that these redox-active metastable phases require activation by fluctuating redox conditions to maintain their high reactivity. In aquatic ecosystems, switching between oxidizing and reducing conditions can be achieved only through hydrological perturbations at hydrological interfaces (for example, water level fluctuations). We present a novel framework that links microscale biogeochemical processes to large-scale hydrological processes, and discuss implications and future research directions for biogeochemical element cycles in aquatic systems exposed to frequent hydrological disturbances.

氧化还原驱动的生物地球化学元素循环在水生生态系统中转换有机物方面发挥着核心作用。它们还执行关键功能，例如去除硝酸盐，减轻温室气体的形成并减弱污染物的影响。最近的研究表明，在这些生态系统中，氧化还原活性化合物的存在是迄今未知的氧化还原特性。这些物质是亚稳态的（即非平衡固相），可以同时提供和接受电子。它们具有很高的氧化还原反应性和可回收性，并且可以通过暂时存储电子来充当生物地电池。然而，它们的寿命是有限的，并且随着时间的流逝，它们变得更加结晶并且反应性降低。在这篇评论中，我们认为这些氧化还原活性的亚稳相需要通过改变氧化还原条件来激活，以维持其高反应性。在水生生态系统中，只有通过水文界面处的水文扰动（例如，水位波动）才能在氧化条件和还原条件之间切换。我们提出了一个新颖的框架，将微观尺度的生物地球化学过程与大规模的水文过程联系起来，并讨论了暴露于频繁水文干扰的水生系统中生物地球化学元素循环的意义和未来的研究方向。