Surfactant-associated bacteria and natural sea slicks in application to satellite oceanography

The sea surface microlayer (SML) is a vital environmental boundary involved in Earth's biogeochemical processes, such as heat, gas, and momentum exchange at the air-sea interface (Carlson et al. 1988, Cunliffe et al. 2013, Liss and Duce 2005). Under favorable conditions, natural slicks form on the sea surface and are visible in synthetic aperture radar (SAR) imagery due to the damping of Bragg waves by surfactants. Surface-active agents (surfactants) reside in the SML and associated subsurface water (SSW) and are the byproducts of life processes of marine organisms such as phytoplankton, zooplankton, and seaweed (Gade et al. 2013); the focus of this work is bacteria. A new approach to reduce contamination during sample collection, handling, and lab processing has been further expanded upon and implemented in this study (Kurata et al. 2016, Hamilton et al. 2015). Microlayer and subsurface samples have been collected in the Straits of Florida and the Gulf of Mexico during Radarsat-2 and TerraSAR-X overpasses. As part of the Gulf of Mexico Research Initiative (CARTHE), over 100 samples were collected in the Gulf of Mexico near De Soto Canyon in February 2016. Quantitative PCR (qPCR) analysis of these samples show a wide variability of relative abundance of Bacillus spp., a well-known surfactant-associated bacteria (Satpute et al. 2010), between the SML and SSW. NextGen sequencing (Illuming MiSeq) results will be analyzed to determine exact bacterial community composition of sea surface microlayer and subsurface samples. We plan to expand our observational sites to several locations in the World Ocean.