jump to navigation

Is the Underwater Oil Gone? August 25, 2010

Posted by Jamie Friedland in Offshore Drilling, Politics.
Tags: , , , , , , , , , ,
trackback

Conflicting reports claim that the giant underwater oil plume in the Gulf of Mexico is both still there and gone.  Yet a closer look at the recent research reveals a potential explanation for this apparent contradiction – and an important new species.

On August 4th, the White House released an official report by the National Oceanic and Atmospheric Administration (NOAA) detailing where the millions of barrels of BP’s spilled oil ended up.  Its conclusion that virtually none of the oil remains suspended in the water column generated some warranted skepticism and justified criticism, particularly in regard to transparency.  Part of the problem was that NOAA considered dispersed/dissolved oil harmless and “gone,” which is how researchers at the University of Georgia could soon after conclude that at least three quarters of the oil is still underwater.  Additional questions have been raised about the peer-review process with which the administration has attempted to fend off these attacks.

Last week, researchers from the Woods Hole Oceanographic Institute published their results from tests conducted in the Gulf on the underwater plume of dispersed oil.  According to their observations, the microbes dispersing the oil were acting very slowly and would likely take months to degrade the full plume.

So it was surprising when researchers from the Lawrence Berkeley National Laboratory announced this week that the oil plume has vanished.   Especially because they reported that the oil was gone because that extra oil had in fact drastically increased microbial oil decomposition.  But how could that be true?  Don’t these studies contradict each other?  As it turns out, not entirely.

It is well established that many types of aquatic microbes can digest oil and already inhabit areas near the thousands of natural oil seeps around the world.  In fact, when the spill first began, some experts were concerned that large amounts of spilled oil could result in a population explosion of a certain toxic species of oil-feeding bacteria that could cause a plague in the Gulf region (E&E News, subscription required).

These two studies both measured microbial activity but arrived at opposing conclusions.  So how can they both be correct?  Was there an orgy of oil-eating microbes or not?  That isn’t yet clear, but it is possible that neither study was wrong.

Bacteria near an oil droplet. Image from Science via Wired.com

It comes down to the methodology, how each study chose to measure microbial activity.  When microbes are exposed to a high concentration of the food they need, they go into metabolic overdrive,  eating and reproducing rapidly.  For these microbes, that food is oil, so an oil spill is a feast.  However, when “aerobic” microbes that use oxygen go into a feeding frenzy, their populations explode and rapidly use up the available oxygen in the water.  Eventually, that area can no longer support aerobic life, including those microbes.  (Side note: this lack of oxygen, called “hypoxia,” is what causes aquatic dead zones at the mouths of most major rivers because they are filled with fertilizer runoff from farms.)

As this excellent Wired.com article explains, the first study measured oxygen levels in the water to gauge microbial activity because if there had been a lot of aerobic oil-eating microbes, the water in the oil plume should contain less oxygen.

The second study used a different approach.  Instead of measuring oxygen levels, they extracted microbial DNA from their water samples and sequenced the genes to see what they do.  These researchers found “large proportions” (which I assume means a high concentration) of genes that create oil-degrading enzymes and, more importantly, discovered a new strain of oil-eating microbe.

This previously undiscovered species is important because it is “anaerobic” – it doesn’t consume oxygen.  It can break down oil without deoxygenating the water around it.  So in the context of that first study, you could consider this new microbe a “stealth” oil-eater; the method employed by first researchers could not have detected its presence.  Additionally, because its growth is not limited by the amount of oxygen in an area, this new species should be more effective and degrade oil more quickly than the aerobic microbes we already knew about.

But just because something is possible does not mean it happened.  Most scientists are wisely urging us not to jump to conclusions.  After all, the oil plume could have just drifted to a different location undetected.  Additional studies are necessary to verify that the oil is in fact gone.

The takeaway message here is that we have an imperfect understanding of underwater oil degradation.  That is part of the reason why BP used all those dispersants – not only did they keep oil-soaked beach/wildlife photos to a minimum, they kept most of the oil dispersed and underwater, where we do not know for sure how much is there or what damage it will cause in the decades to come.  It’s hard to sue a company for unknown damages.

So let’s take this study as some welcome good news, but keep our hopes in check until we can confirm these results.  And figure out how dangerous dispersed oil is.

Advertisements

Comments»

No comments yet — be the first.

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s

%d bloggers like this: