The role of bacterioneuston in air-sea microlayer biogeochemistry of organic matter

海水表面是海气相互作用的直接场所，因此，海洋表面的性质可能极大地影响海洋与大气之间的气体、热量和颗粒交换。疏水有机分子集中在水的表面形成气海微层（ASML），该微层已被证明含有与底层水不同的微生物群落（细菌群/ BN）。目前测量ASML生物学特性的方法包括初始去除和收集BN。我们建议使用一根玻璃管水平地浸泡在地表水中，在用两个硅胶管塞住之前，向侧面切开一个完整的ASML，作为孵育装置。本研究的主要目的是开发一种能够测量完整ASML中BN代谢率的方法，使用放射性同位素标记的脂肪酸示踪剂。标记的脂肪酸气态代谢物将通过鼓泡空气通过设备的顶部空间收集，并进入选择性捕获二氧化碳或氚化水的陷阱。由于氮化硼可能影响完整ASML的物理化学过程，因此将使用氚化水作为示踪剂来检查其对蒸发速率的影响。将与不存在BN的样品、BN已中毒的样品和含有BN的ASML已在超薄硝化纤维素膜的帮助下去除的样品进行比较。利用细胞分选装置/流式细胞仪对BN细胞进行特异性防水染色，使其与浮游细胞分离。BN细胞将通过分类群特异性分子探针的选择性标记在显微镜下进行鉴定。在使用当地海水样本之前，这些方法将首先在海洋细菌培养物上进行测试。预计所开发的方法和设备最终可用于测量完整海洋asml中的BN代谢率。测定的生物地球化学通量将通过ASML与物理化学通量进行比较，以促进目前对影响全球气候变化的海气界面过程的认识。

The seawater surface is the direct site of air-sea interactions and as such, the properties of the surface ocean may greatly influence the exchange of gases, heat and particles between the ocean and the atmosphere. Hydrophobic organic molecules are concentrated at the surface of the water to form the air-sea microlayer (ASML) that has been shown to harbour a different microbial community (bacterioneuston / BN) relative to the underlying water. Current methods of measuring biological properties of the ASML involve the initial removal and collection of BN. We propose to use a glass tube horizontally half immerged in surface water and sliced sideward through an intact ASML before being corked with two silicone bungs to become an incubation apparatus. The main aim of this proposed research is to develop a method capable of measuring metabolic rates of BN in the intact ASML, using radioisotopically labelled fatty acid tracers. Labelled gaseous metabolites of fatty acids will be collected by bubbling air through headspace of apparatuses and into traps selectively capturing CO2 or tritiated water. Because BN may influence physicochemical processes across the intact ASML, the effect on evaporation rates will be examined using tritiated water as a tracer. Comparisons will be made with samples where BN are not present, BN have been poisoned and samples where the ASML including BN has been removed with the aid of an ultra-thin nitrocellulose membrane. BN cells will be specifically stained with water-repellent dyes to separate them from planktonic cells using a cell sorting device / a flow cytometer. BN cells will be identified microscopically by selective labelling with taxon-specific molecular probes. These methods will be tested initially on marine bacterial cultures before using local seawater samples. It is anticipated that the methods and apparatus developed could be eventually used to measure BN metabolic rates in the intact oceanic ASMLs. The determined biogeochemical fluxes will be compared with physicochemical fluxes through the ASML to advance current understanding of the air-sea interface processes which affect global climate change.