BP oil spill killed off beach microbes, damaging entire ecosystem

Tuesday, December 01, 2015 by: David Gutierrez, staff writer
Tags: BP oil, Deepwater Horizon, oil spill

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(NaturalNews) The 2010 BP (Deepwater Horizon) oil spill caused long-lasting damage to the microbial ecosystem of Gulf beaches, suggests a study conducted by researchers from Georgia Tech and published in the ISME Journal on February 17.

The April 2010 spill was the worst offshore oil spill in U.S. history. It began when the Deepwater Horizon drilling rig exploded, killing 11 workers and sending 5.0 million barrels (210 million gallons) of oil gushing into the Gulf of Mexico.

The researchers found that although much of the oil that washed ashore following the spill was broken down by soil bacteria, most species of bacteria were killed by the contamination. This left the overall soil ecosystem - the foundation of the larger ecosystem - much less diverse. Nitrogen-fixing bacteria in particular were hard hit.

The study was partially funded by BP.

Support base of ecosystem destroyed

The researchers compared samples taken in May 2010, just before the oil reached the Florida panhandle, with samples taken just after it arrived (July and October 2010), as well as a year later (June 2011). They found that, as expected, the prevalence of hydrocarbon-digesting bacteria increased in the short term. Over the longer term, however, the numbers of these bacteria declined again, presumably as they used up the extra food.

The microbial ecosystem left behind a year after the spill did not, therefore, benefit oil-digesting bacteria. Instead, it benefited generalist bacteria who were able to digest enough hydrocarbons to not be killed off in the initial influx, but not to starve when the oil was used up.

"It seems to be the case that the generalists, those that can carry out many different functions, are better equipped to deal with oil spills, compared to some specialists, which is what some people would think," co-author Konstantinidis Konstantinos said.

One of the major groups of bacteria to be devastated by the spill were nitrogen-fixers, which turn nitrogen from the air into a form that can be used by other life forms (such as plants and, by extension, animals). These bacteria are essential for maintaining a healthy, diverse terrestrial ecosystem.

"One of the key groups that we saw disappearing, from the oil, was these nitrogen fixers," Konstantinos said. "That's a concern because it supports the rest of the system."

Ongoing effects of disaster

The good news of the study was that within about a year, most of the oil was gone from the Florida beach that was tested.

"One year later, we see very little oil - a lot was apparently degraded by the microbes that live in the beach sand," Konstantinos said. "The microbes in the beach sand seem to do a good job, biodegrading and removing the oil."

The bad news is that it remains unclear how long it will take the ecosystem to recover. A June 2012 study in the journal PLoS ONE also found significantly reduced species richness in non-bacterial soil organisms, including algae, protists, fungi and simple animals such as nematodes.

"Based on this community analysis, our data suggest considerable (hidden) initial impacts across Gulf beaches may be ongoing, despite the disappearance of visible surface oil in the region," the researchers wrote.

A more recent study, published in the Proceedings of the National Academy of Sciences in November 2014, estimated that 1.8 million barrels of oil continue to contaminate the ocean sediment at depths below 900 meters in a 3,200 square kilometer area around the ruptured well. The sediment settled in a patchwork pattern that made it difficult to locate.

"We also suggest that a significant quantity of oil was deposited on the ocean floor outside this area but so far has evaded detection because of its heterogeneous spatial distribution," the researchers wrote.

Sources:

http://www.latimes.com

http://journals.plos.org

http://www.pnas.org/content/111/45/15906.abstract