Oil dispersant, too good to be true?

Effects of oil spills and chemical dispersant on deep-water shipwrecks and their associated microorganisms are largely unknown. Salerno et al. (2018) investigated this by using bioinformatic analysis of sequenced 16S rRNA gene amplicons to study biofilm growth on Carbon steel disks (CSD).  Investigating the impacts of oil and dispersant when present. Metal corrosion of these disks was characterised using ESEM and EDS. Oil-dispersant and oil treated CSDs were shown to have roughly twice the number of hydrocarbon-degraders compared to the control. Corrosion in these treatments was also greater due to presence of bacteria used in bioremediation from the Pseudomonas genus which can also produce hydrogen sulfide.

Other studies have shown that biofilms in the presence of dispersed oil have elevated amounts of stress response genes and greater growth rates. This indicates a community response under adverse conditions causing biofilms to thrive. However, this study shows although there may be proliferation of biofilms, residue oil effects are severe compromising shipwrecks as habitats due to increased corrosion, and disrupting community compositions, putting into question the effectiveness of dispersants. One criticism of this study is their use of only one metal alloy as an artificial habitat as different shipwrecks can be made of varying metals so levels of corrosion and colonisation may vary.

Salerno J.L., Little B., Lee J., Hamdan J.L., (2018) Exposure to Crude Oil and Chemical Dispersant May Impact Marine Microbial Biofilm Composition and Steel Corrosion.  Frontiers in Marine Science.5. doi:10.3389/fmars.2018.00196