Oil formations take toll on microbes

Oil compounds are found in surface slick, droplet, and dissolved forms after spill events. Combinations of these forms influence the variability of microbial responses to oil aggregations. Researchers can create environments knows as ‘WAF’s, where oil is present in all forms mentioned above, and ‘WSF’s, with oil in a dissolved form only. In an interesting and thorough study, Bera et al. (2019) use these two environments in mesocosm set-ups to identify the impact different oil aggregations have on bacterial community composition, phytoplankton productivity, and the abundance of exopolymer particles.

16S rRNA sequencing revealed differential bacterial community structures between WAF and WSF treatments, with different OTUs enriched in each treatment. This may be explained by hydrocarbon-degrading bacteria preferring readily available oil droplets (for faster biofilm formation) in the WAF treatment, which aren’t present in WSF. Analysis of chlorophyll α fluorescence shows consistent phytoplankton communities across both treatments. Reduced electron transport and growth rates in the WSF treatment, however, indicate dissolved PAHs have a damaging effect on phytoplankton photosystems. TEP production was higher in WSF compared to WAF, potentially due to phytoplankton increasing polysaccharide-rich substance release in times of stress. The information provided above is just a snapshot of the knowledge gained from this study, and I imagine it will be extremely high impact.

Bera, G., Doyle, S., Passow, U., Kamalanathan, M., Wade, T. L., Sylvan, J. B., ... & Knap, A. H. (2019). Biological response to dissolved versus dispersed oil. Marine pollution bulletin, 110713.
https://www.sciencedirect.com/science/article/pii/S0025326X19308690