Natural oil seeps in the Gulf of Mexico and the microbes who love them

Microorganisms and phytoplankton appear to thrive in the waters around naturally occurring oil seeps on the Gulf floor.

First Look

Naturally seeping oil, in a small amounts, can actually contribute to growth in phytoplankton, according to researchers.

Researcher Ajit Subramaniam, an oceanographer at Columbia University’s Lamont-Doherty Earth analyzed the effects natural oil seeps on microorganisms in the Gulf of Mexico, and found that microorganisms called phytoplankton were twice as concentrated in areas where oil was seeping naturally than clearer waters, in a paper published online Monday in the journal Nature Geoscience.

“This is the beginning of evidence that some microbes in the Gulf may be preconditioned to survive with oil, at least at lower concentrations,” said Professor Subramaniam in a press release. “In this case, we clearly see these phytoplankton are not negatively affected at low concentrations of oil, and there is an accompanying process that helps them thrive. This does not mean that exposure to oil at all concentrations for prolonged lengths of time is good for phytoplankton.”

Subramaniam based his study on a new set of data that was released by researchers from Florida State University.

The Florida State University researchers were trying to determine the amount of oil that seeps into the Gulf naturally and the amount that came from the Deepwater Horizon spill in 2010. They established that 4.3 million barrels were released into the Gulf from the oil spill, compared to 160,000 to 600,000 barrels per year that is released from naturally occurring seep.

“This information gives us context for the Deepwater Horizon spill,” said Ian MacDonald, an oceanography professor at Florida State University, in the release. “Although natural seeps are significant over time, the spill was vastly more concentrated in time and space, which is why its impact was so severe.”

“It’s giving us a basis for all of these other experiments,” Professor MacDonald added. “It’s really revolutionizing how we look at the Gulf. It also gives scientists the exact geographic points where oil from the spill was located, so researchers can go to the Gulf floor and explore the area to see if there has been any environmental effect.”

Using a synthetic aperture radar (SAR), researchers studying the effect of natural oil seeps on phytoplankton were able to get a detailed picture of where the oil and gas seeps are formed across the Gulf of Mexico. The highest phytoplankton concentration was located several hundred feet below the water surface, where the microorganisms could thrive on the amount of rising nutrients and sunlight that penetrates from the above.

Through a series of laboratory experiments, the researchers established that phytoplankton do not receive any benefit from any amount of oil, but are capable of tolerating the oils low concentrations.

Michael Behrenfeld, a marine ecology professor at Oregon State University in Corvallis who is not affiliated with the study, suggests in companion commentary published in Nature Geoscience that this research could spur similar studies in other areas of the world.

"With hydrocarbon seeps common along many continental margins, and even under Antarctic ice shelves, it will be interesting to see how this bubbling deep ocean brew is altering surface phytoplankton dynamics in other regions of the world's ocean," Professor Behrenfeld writes.