UC San Diego

Seafoam is a common existence of floating bubble patches on the sea surface. The injection of air into the sea surface causes bubbles, and the surface-active compounds, also known as surfactants, are of vital importance in the formation of it. The sources of surfactants fall into bacteria, algae, and other marine organisms in the sea surface layer. However, the environmental mechanisms behind the foam formation in smaller events are unclear, including what roles bacteria and eukaryotes might play. After analyzing the 16S and 18S microbial communities of the seawater and foam samples, Pseudoalteromonus was characterized as the most abundant bacteria strains in the foam, which shows a significant difference from the abundance in the seawater. Cercozoa was detected as the most abundant eukaryote in seafoam, while Stramenopiles is another dominant group in all samples. The microbial diversities from different foam samples were highly different from each other, which means the sources of surfactant were important for the formation and were different between every foam event. Both bacterial strains and diatom strains from foam samples were isolated and cultured in the lab. Pseudoalteromonus, Cobetia, Vibrio, Winogradskyella were known as biosurfactant producers. Qualitative and quantitative analyzes of the surfactant composition in samples should be conducted in the future to figure out the capacities of bacteria and diatoms to produce the foam.