SP 1.5 Molecular characterization of dissolved organic matter in the sea surface microlayer (SML) and its influence on the inorganic carbon cycle

我们的动机是了解溶解有机物(DOM)作为影响海-气交换、碳酸盐化学和相关生物的生态系统功能的关键成分在SML中的作用(Engel等人，2017年)。在我们的初步工作中，我们在SML中发现了DOM和碳酸盐化学之间尚不清楚的联系的迹象，以及DOM组成中的高时空动力学的迹象。然而，尽管表面上看起来是短暂的，SML-DOM几何代谢体(即由生物和非生物过程产生和修改的整个DOM池)在很大程度上仍然是未知的领域。此外，由于在不同的环境和实验条件下从更大范围的研究地点获得的数据有限，以及缺乏结合物理、地球化学和生物学的跨学科研究，阻碍了对DOM在SML中划分为不同化学部分背后的驱动力的机械性理解。换句话说，我们从地球上最大的空气-水界面上遗漏了基本的(有机)地球化学信息，与气候相关的气体交换的后果未知。在这个项目中，我们试图通过对DOM组成和无机碳系统参数的互补测量来填补这一空白。与研究单位BASS的相关性源于我们的子项目的目的是提供SML-DOM清单中缺失的基本生物地球化学信息，并将其与SML生态系统过程联系起来，包括DOM生产(SP1.1)以及微生物(SP1.2)和光化学(SP1.4)周转。此外，我们将研究DOM几何代谢对SML酸碱平衡的贡献，我们预计这将影响界面上的气体平衡--特别是碳酸体系内的气体平衡--从而影响温室气体通量(SP2.1)。

Our motivation is to understand the role of dissolved organic matter (DOM) in the SML as a key component influencing air-sea gas exchange, carbonate chemistry, and ecosystem functioning of associated organisms (Engel et al., 2017). During our preliminary work, we have found indications for a yet unknown link between DOM and carbonate chemistry in the SML, as well as for high spatio-temporal dynamics in DOM composition. However, despite its apparent ephemeral character, the SML-DOM geometabolome (i.e., the entirety of the DOM pool that is produced and modified by biotic and abiotic processes) is still largely uncharted territory. Further, a mechanistic understanding of the driving forces behind DOM compartmentalization into distinct chemical fractions in the SML is hindered by the limited availability of data from a larger range of study sites under differing environmental and experimental conditions, as well as a lack of interdisciplinary studies combining physics, geochemistry, and biology. In other words, we are missing basic (organo-)geochemical information from the largest air-water interface on earth, with unknown consequences for the associated exchange of climate-relevant gases. In this project, we seek to fill this gap by complementary measurements of DOM composition and inorganic carbon system parameters. Relevance to the research unit BASS stems from the aim of our subproject to provide the missing basic biogeochemical information of the SML-DOM inventory, and set it into context with SML ecosystem processes including DOM production (SP1.1) as well as microbial (SP1.2) and photochemical (SP1.4) turnover. Furthermore, we will examine the contribution of the DOM geometabolome to the acid-base balance of the SML, which we expect to affect gas equilibria in the interface—within the carbonic acid system in particular—and therefore, impact greenhouse gas fluxes (SP2.1).