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会极大地影响海洋和大气之间的气体、热量和颗粒的交换。疏水性有机分子集中在水面形成的空气-海洋微层（ASML），已被证明窝藏不同的微生物群落（细菌浮游生物/ BN）相对于底层水。目前测量ASML的生物学性质的方法涉及BN的初始去除和收集。我们建议使用一个玻璃管水平一半浸入地表水，并通过一个完整的ASML被软木塞之前，两个硅胶塞子，成为一个孵化器侧向切片。这项研究的主要目的是开发一种方法，能够测量BN的代谢率在完整的ASML，使用放射性同位素标记的脂肪酸示踪剂。将通过使空气鼓泡通过装置的顶部空间并进入选择性捕获CO2或氚化水的捕集器来收集脂肪酸的标记气态代谢物。由于BN可能会影响整个完整的ASML的物理化学过程，对蒸发速率的影响将使用氚水作为示踪剂进行检查。将与其中BN不存在的样品、BN已中毒的样品和其中ASML（包括BN）已借助于超薄硝酸纤维素膜去除的样品进行比较。BN细胞将用防水染料特异性染色，以使用细胞分选装置/流式细胞仪将其与嗜酸性细胞分离。BN细胞将通过用分类群特异性分子探针选择性标记在显微镜下鉴定。这些方法将首先在海洋细菌培养中进行测试，然后才使用本地海水样本。预计开发的方法和仪器最终可用于测量完整海洋ASML中的BN代谢率。将通过ASML将确定的地球化学通量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理解。

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.