Microbial Effects on the Production and Transformation of Surfactants Within the Microlayer and Subsurface Waters in Application to Remote Sensing Techniques

摘要

The sea surface microlayer is a millimeter-scale interfacial layer between the atmosphere and the ocean. A number of studies have suggested that there is a unique ecosystem for marine bacteria in the sea surface microlayer, but little information exists on the microbial community composition of this ecosystem due to sampling complexities. In this work, we present an improved method to sample and compare the bacterial diversity of the sea surface microlayer with that of subsurface water at the same site. Bacterial samples were collected from the sea surface microlayer with a sampling method, which minimized sample contamination from the research platform and the subsurface water. Sampling was conducted using a polycarbonate membrane filter to obtain the bacterial community structure at open water and coastal water sites in the Straits of Florida. The microlayer sampling was planned to coincide with synthetic aperture radar satellite overpasses (COSMO SkyMed), which capture a range of fine-scale features on the sea surface. The presence of surfactants affect the synthetic aperture radar imaging process because surfactants in the sea surface microlayer suppress short gravity-capillary ocean surface waves, thereby decreasing the backscatter and allowing the radar to detect surfactant-covered areas. Although sources of surfactants vary, certain marine bacteria are known to produce and transform surfactants, which suggest that these surfactant-related marine bacteria have an important biological influence on fine-scale synthetic aperture radar satellite imagery. Therefore, the comparison between synthetic aperture radar satellite images and in situ field samples may be used for interpreting and studying fine-scale features on the sea surface. The surfactant-associated bacterial composition of the sampling sites was determined using high-throughput, 454 pyrosequencing methods. A total of 61,663 sequences were analyzed and the results indicated the presence of surfactant-associated bacteria such as Moraxellaceae, Halomonadaceae, Enterobacteriaceae, Bacillaceae, and Nocardiaceae. By establishing these bacterial groups that influence the presence of surfactants, remote sensing techniques which involve monitoring the microlayer are expected to be enhanced and may provide additional information on the state of the upper ocean ecosystem.