DNA Analysis of Surfactant-Associated Bacteria in a Natural Sea Slick Observed by TerraSAR-X and RADARSAT-2 Over the Gulf of Mexico

The damping of short gravity-capillary waves (Bragg waves) due to surfactant accumulation under low wind speed conditions results in the formation of natural sea slicks. These slicks are detectable visually and in synthetic aperture radar (SAR) imagery. Surfactants are produced by natural life processes of many organisms, such as bacteria, phytoplankton, seaweed, and zooplankton. By using DNA analysis, we are able to determine the relative abundance of surfactant-associated bacteria in the sea surface microlayer and the subsurface water column. A method to reduce contamination of samples during collection, storage, and analysis (Kurata et al., 2016; Hamilton et al., 2015) has been implemented and advanced by increasing the number of successive samples and changing sample storage procedures. In this work, microlayer samples have been collected in the Gulf of Mexico during a research cruise (LASER) on the R/V F.G. Walton Smith during RADARSAT-2 and TerraSAR-X overpasses. We found that in slick areas surfactant-associated bacteria mostly reside in subsurface waters, producing surfactants, which move to the surface, accumulate on and enrich the sea surface microlayer. This is consistent with previous studies (Kurata et al., 2016; Hamilton et al., 2015) and with the experimental results of Cunliffe et al. (2010).