Marine foams represent compressed sea-surface microlayer with distinctive bacterial communities

Abstract The occurrence of foams at the oceans' surface is patchy and generally short-lived. Here we investigated if marine foams as important sea surface phenomena represent a compressed form of the sea-surface microlayer (SML), a <1 mm thick film at the air-sea interface. To date, the bacterial community composition of sea foams, the bacterial role in the foam formation process and community differences to SML and underlying water remains predominantly unknown. Our study deals with the microbial composition of foams, SML and subsurface samples (1-m depth) collected from the North Sea and Indian Ocean. Foams were characterized by increasing abundance of small phototrophic and prokaryotic cells as well as high concentrations of surface-active substances (SAS). Amplicon sequencing revealed distinctive bacterial communities in foams compared to the other two habitats including species of Persicirhabdus and Winogradskyella belonging to particle-attached communities. Comparison of rRNA and DNA based sequenced data suggested that Pseudoalteromonas sp. are highly active and thus might enhance foam formation and stability by producing SAS. Presence of motile Vibrio might argue for active migration towards nutrient-rich foams. Our study shows that foam bacteria might contribute to foam formation with major implications for air-sea exchange processes, biogeochemical cycling and food web functioning.

摘要 海洋表面泡沫的分布呈斑块状，且通常存续时间较短。本研究旨在探究作为重要海面现象的海洋泡沫，是否为海表面微层（sea-surface microlayer, SML）的浓缩形式——后者是气-水界面处厚度不足1毫米的薄膜。迄今为止，海洋泡沫的细菌群落组成、细菌在泡沫形成过程中的作用，以及其与SML和下层水体的群落差异，大多仍未明确。本研究针对从北海与印度洋采集的泡沫、SML以及次表层（水深1米）样本的微生物组成展开分析。泡沫的特征为小型光合细胞与原核细胞的丰度升高，同时伴随高浓度的表面活性物质（surface-active substances, SAS）。扩增子测序结果显示，与另外两种生境相比，泡沫中的细菌群落具有显著特异性，其中包括隶属于附粒群落的Persicirhabdus属与Winogradskyella属物种。基于rRNA与DNA的测序数据对比分析表明，Pseudoalteromonas sp. 具有极高的活性，或可通过分泌SAS促进泡沫的形成与稳定。具有运动能力的弧菌（Vibrio）的存在，或表明其会主动向营养富集的泡沫迁移。本研究表明，泡沫中的细菌可能参与泡沫形成，这对气-水交换过程、生物地球化学循环以及食物网功能均具有重要意义。