One critter's poison may be another one's dinner, even at the microbe level.
One month after the April 2010 Deepwater Horizon oil spill, the Gulf Coast’s beaches were home to a diversity of microscopic, cellular microbes, such as protists, nematodes, and fungi. But by September 2010, potential hydrocarbon-eating fungi dominated many of the same sites, according to a new study.
Bik and her collaborators found that the marine communities shifted from communities comprised of largely microbial worms to ones dominated by a few species of fungi. And these new fungal communities weren't of the garden variety, but instead ones that use hydrocarbons to thrive in hostile, polluted conditions. The results of the study were published online June 6 in PLoS ONE.
To make this discovery, Bik and her collaborators collected samples from the beaches near Dauphin Island, AL, and Grand Isle, LA, in May and September of 2010. First, the team sifted the tiny eukaryotes from the sediment and broke open their cells to collect the DNA. Then, they ran the genetic material through a high-throughput gene sequencer to identify the microbes existing at each sample site. To double-check the genetic analysis, the scientists also used microscopy to classify the species in the sediment samples.
After analyzing 1.2 million DNA sequences and long hours at the microscope, the team concluded that the communities sampled at the same sites weren’t closely related to each other before oil hit shore versus after oil hit shore. The post-spill samples had a large number of hydrocarbon-eating fungi, with a mix of predatory, scavenger, and juvenile nematodes.
The "most convincing" sign that oil affected the sediments was from the data taken at Grand Isle and Shellfish Lab, sites 250 miles apart, Bik said. According to photos of the beaches, these two sites looked completely different after the spill. In September 2010, Grand Isle was covered in oil, while Dauphin Island looked untouched. Still, the DNA analysis showed that both sites had the same types of fungi dominating the microbial community after the oil spill. The results suggest that both sites experienced an environmental disturbance, even though Dauphin Island looked unharmed, and that the oil spill could have left other hidden effects.
With additional analysis, the scientists hope to determine if the fungal communities thrived because of the spilled oil or mechanical beach cleanup methods and whether the new communities survive long-term, fluctuate with the seasons, or return to their pre-spill diversity. Bik is also interested in looking more deeply into the genomes of the fungal species found on post-spill beaches. If the fungi's genetic machinery indicates that they can breakdown hydrocarbons, finding the relevant genes may be useful for future bioengineering and bioremediation research.
- Bik H.M., Halanych K.M., Sharma J., Thomas W.K. (2012) Dramatic shifts in benthic microbial eukaryote communities following the Deepwater Horizon Oil Spill. PLoS ONE 7(6): e38550.