Pensacola Beach 16S Amplicon Sequences Raw sequence reads. beach sand metagenome

Photodegradation by sunlight and microbial activities control decomposition of hydrocarbons deposited in shore sediments after oil spills, with temperature, moisture and availability of oxygen being central rate-limiting factors. One month after crude oil from the Deepwater Horizon accident started washing onto northeastern Gulf shores on June 22nd, hydrocarbons contaminated the beach at Pensacola (FL) down to 55 cm sand depth, producing an environmental hazard with unknown fate. Here we show that beach breathing facilitated aerobic decomposition of the buried oil at rate constants of 0.02 to 0.03 d-1, similar to those reported for non-fossil organic matter in soils. This breathing, driven by vertical tidal groundwater oscillation, supplied oxygen to a bloom of aerobic bacteria that developed within 3 weeks in the deep oiled layers. Opposing vertical gradients of temperature and moisture supported growth conditions in the contaminated subsurface layers leading to a dominance of oil-degraders and a decrease of the general microbial diversity. Within a year of oil contamination, GC-MS amenable hydrocarbons in the beach had decreased and microbial diversity increased to pre-spill levels. The results underline the role of tidal sandy beaches as effective cleaning bioreactors at the land ocean interface.