How the 2010 Deepwater Horizon Oil Spill Altered Gulf Microbial Communities

A recent study by a team of researchers led by Holly Bik has found that the 2010 Deepwater Horizon oil spill altered Gulf microbial communities, including species such as metazoan phyla, protists, algae, and fungi. These organisms are the basis of the entire ocean ecosystem, and are essential for nutrient cycling and sediment stability. The research was conducted on-site and at the University of New Hampshire’s Hubbard Center for Genome Studies (HCGS).

The study compared beach samples from Grand Isle, Louisiana, and Dauphin Island, Alabama, taken during 2 different time periods. The first set of samples were taken in May 2010, shortly after the Deepwater Horizon oil spill began but before the oil reached the shore. The second set of samples were taken in September 2010, several months after the oil reached the shore. Researchers examined the samples by using high throughput gene sequencing and checking the results against an under-the-microscope taxonomic approach.

Analysis of the samples showed a drastic change in the microbial community after the oil spill. Before the spill, the microbial eukaryotes in the beach sediments consisted of highly diverse communities dominated by nematodes, which is typical of a beach microbial community. After the oil reached the shore, the microbial population consisted almost entirely of specialized fungi.

These fungi belonged to taxa which are believed to be able to metabolize hydrocarbons. This made the polluted conditions in the Gulf of Mexico favorable to these fungi, while being unfavorable or even intolerable to most other marine protazoa. Similar taxonomic biases have been found by previous studies which examined hydrocarbon contamination in marine habitats.

Other changes in the Gulf microbial communities included an increased number of predatory and scavanger nematodes, as well as an increased number of juveniles. Some of these nematodes are able to utilize alternative food sources, including direct uptake of dissolved carbon. This would give them a competitive advantage in oil-affected regions, which are high in hydrocarbons. This change also alters their functional roles within microbial eukaryote communities.

Although Grand Isle was visibly covered in oil during the second set of sampling, 2 months after the Macondo leak was capped, there was very little visual evidence of oil on Dauphin Island. This may be because Dauphin Island was more sheltered than Grand Isle from the direction of the spill. The microbial changes on both beaches were similar, but Dauphin Island showed greater diversity in its microbial community than Grand Isle.

This research confirms the findings of a 2010 preliminary report to the U.S. Coast Guard. The earlier report also found microbes which were capable of degrading oil and related hydrocarbons in the contaminated areas. It is still not known whether the shift in microbial communities on Gulf shore beaches is ephemeral, seasonal, or permanent.