Bacteria devoured methane gas from gulf oil spill, scientists say

Last August, just two days into a research cruise to study methane gas spewed into the Gulf of Mexico by the Deepwater Horizon gusher, Texas A&M University oceanographer John Kessler turned to one of his colleagues and said, "Well, it looks like it might be gone. What do you think?"

The huge wallop of methane burped up from deep inside the earth was, in fact, missing.

Kessler and his colleagues now report in Science that a huge swarm of gas-gobbling bacteria swelled to consume nearly all of the estimated 200,000 tons of methane dumped into the gulf. .....

Besides providing some good news for the gulf region, the finding has potential implications for climate change science, too. Methane is a much more potent greenhouse gas than carbon dioxide, and, as the earth warms, climate scientists worry that much more methane will be released from the oceans. "What this tells us is that natural releases of methane from the seafloor with similar characteristics will not make it up to the atmosphere, will not influence climate," Kessler says.

While the gusher was still flowing, in June, a team sponsored by the National Science Foundation and the National Oceanic and Atmospheric Administration had found intense concentrations of methane in the waters near the wellhead, ..........At the time, that team detected very few of the methane-eating bacteria that naturally live in the gulf. So Valentine and colleagues arrived at a grim - though early - conclusion. "Originally, we had expected that the methane would be consumed gradually," Valentine says. "We really thought it would be around for a year or more."

Instead, two to three months after engineers finally capped the well, the gas was gone. All of the evidence points to an explosion of methane-eating bacteria.

Let’s say you’re right:

(1) fish need 5 PPM of dissolved O2 (in round numbers) to live in relatively warm waters. Agreed. That does coincidently equate to your figure of about 5 mg/L. Deep ocean species need less, warm water fishes might need more. But we can go with the 5 mg/L figure. Apples and oranges. What’s your point? You have merely pointed out that methane CAN be a solute at higher concentrations than the minimum O2 levels required to support aquatic life. Relevance?

BUT...

(2) Methane is NOT toxic, nor is it suffocating as a solute in water. The mere presence of dissolved methane is NOT a problem. Please cite a reference for how methane directly harms fish. I don’t even know what “quite high enough” or “significantly biologically effective” means or why it is in quotes in your post. Again, demonstrate in fact that ANY concentration of dissolved methane (up to amounts encountered in the Gulf) is a PROBLEM. Being smug— (on my part) the concentration of H2O is highest of all! ... and that’s not a problem.

What is it you want me to agree to that I have not yet acceded to?

Again, my point on this post/thread is twofold—

(1) Methane, according to my sources is, expressed in moles per litre, among the least soluble atmospheric and/or aquatic/marine natural gases. and (2) I have yet to see how the mere presence of higher-than-normal levels of dissolved methane is a PROBLEM in the marine ecosystem because it is NON-toxic.

As an aside, you’ll note I prefer to employ a solubility number expressed in moles (micro moles actually) per litre, because comparing solubility by mass (mg) can be misleading due to the difference in molecular weight of 02 versus CH4.

Now I’ll move to your next post.

Please permit me to refer to the “money quote” from the article: “two to three months after engineers finally capped the well, the gas was gone. All of the evidence points to an explosion of methane-eating bacteria.”

Per the article, HOW MUCH of the evidence points to an explosion of methane-eating bacteria? The author wrote “all” and that is a preposterous and scientifically unsound statement. An accurate statement is that the data support the idea that bacteria contributed to the disappearance of released methane. The scientist has models demonstrating the plausibility, but does NOT appear to have data demonstrating the fact. Coincidence is not causality. The fact that data align do not mean they are IN the same equation.

Were biological mechanisms at work to metabolize tons of released hydrocarbons? Absolutely. Were the laws of physics and chemistry at work to dissipate and disperse (and otherwise render harmless) tons of released chemistry? Absolutely.

I stick with my assertion that physics and chemistry (and ocean mechanics) were FAR more responsible for the dissipation of the methane than methanotrophic bacteria were. I’ll stick with that until I see evidence from water samples demonstrated a bloom and subsequent death of so-called “beneficial bacteria.” The article points out that the scientists, who DID do some good work, used inferential methods, DNA sequencing and math models to infer that bacteria could have done it. So he has a hypothesis and some data and (unfortunately) reached some eye-popping conclusions that ‘bacteria MUST be the cause ‘cuz my original thesis was blown away by the data I found.’ Thus the debate. The article ALSO points out that the data he encountered (ie NO methane and NO problems from it) did not support his original investigative hypotheses. Gee, that sounds like global warming research. I’ll give the guy credit though for looking hard at the data and trying to figure out what happened.

Note: I think you know this but ... I say bloom AND DEATH because when a nutrient is temporarily introduced into a “food chain” the affected hungry populations do increase ... and then starve and die when the temporary food is exhausted. WHERE is the evidence, excuse me “all the evidence” that points to a bacterial bloom? This researcher found DNA indicating the bacteria were there (they are ALWAYS there) and used oxygen measurements to infer that ‘the bacteria did it’ ... even though he didn’t present bacterial count data. Granted this guy and his team might not be biologists/bacteriologists, but that just weakens their claim. I agree that it COULD BE. It’s a relatively plausible hypothesis. But just because the data you encounter (wow, the CH4 sure went away fast) doesn’t fit the reason you went to sea DOES NOT mean your conclusions are correct. The right thing to do is, at the next spill, is do population studies on the methanotrophs in the area and DEMONSTRATE with data that indeed, “all the evidence” points to nature’s dust brooms.

You wrote “drastically faster than could be attributed to the normal laws of physics.”

I would argue it was simply drastically faster than this scientist had modeled. As a scientist you build models all the time that are blown away by what you encounter in real life. The article (blame the WAPO) is littered with AGW phrases. I still believe the author tried to imply things the scientist did not.

You wrote you disagree with my “... assertion that it was impossible for the drastic decrease in methane concentration to be due to beneficial bacteria.”

I stick with that assertion yet clarify it to say that indeed ALL parts of nature worked to dissipate gaseous methane. To me this was MOSTLY like an open can of pop that went flat faster than the models projected. Go figure.

The laws of physics (gas laws) work faster than bacteria physiology. The Gulf water-atmosphere boundary is an OPEN system: dissolved gases dissipate, and so does the gas that bubbled to the surface. AND the warmer the water, the less soluble ANY gas is (vapour pressure).

Indeed some measure of the gaseous methane dissolved. How much can be estimated. Some of that was certainly biologically consumed. Virtually ALL naturally occurring hydrocarbons ARE broken down by SOME member of the diverse food chain. An old axiom of biology is that if a survivable niche exists, an organism will evolve to fill it — thus bacteria that ‘eat’ methane and sulfur; even some that ‘eat’ iron and degrade shipwrecks (in addition to rust.)

You wrote “The whole point of the posted article was that the rate of decrease was drastically faster than could be attributed to the normal laws of physics “

When I made my very first post in this thread I pointed out that I did not read the entire article ‘cuz it pi$$ed me off so bad with the money quote. I have since read the article. To your point I need to be fair and ding the WAPO writer, not so much the scientist. The scientist was clear to point out that the CH4 went away faster than he modeled, and was looking for why, and came up with this theory, which his data appear to support. The author ran with it a ‘bridge too far.’

You wrote: “The article itself does not EVER imply that the reductions in dissolved O2 were “disastrous”.

Actually O2 level in the Gulf *ARE* a real issue. Agricultural run off has contributed to large dead zones, persistent ones. The scientist measured O2 levels as a ‘canary in the coal mine.’ But you are right, the article is not directly about this. On that we agree.

You wrote: “And I said exactly nothing about the methane release being a disaster, so any comments you make to that point are simply your imagination.” I did not mean to put words in *your* mouth. But ... Concerned and well-meaning environmentalists ARE very worried about methane in the environment and its increases — due to everything from cow farts and termites to Amazon forest clearing and oil spills. “THEY” went there looking for trouble. I don’t know if this particular scientist went there looking for trouble or just data, Clearly to the WAPO has a history of bandwagon journalism in this area, and I was admittedly ranting a bit because CH4 is NOT a problem for a marine ecosystem. NET: YOU did not say CH4 was a disaster, but others have and I was reacting to that.

NEXT:
You wrote: “What appears to be the case is that a huge amount of “bacteria-food” (methane) was released, the bacteria ate it, and in turn were eaten by something else (probably other bacteria, or microfauna), and are no longer there. A totally natural progression.”

While “huge” is a subjective term, I’ll agree that nature worked its course, and bacteria contributed to the clean-up. I think I’ll continue to ‘believe’ the bacterial impact was small until I see better direct evidence studies. [ then I’ll agree the earth does indeed orbit the sun ;-) ] Until then I’ll stick with my placards which read “methane is not a marine problem” and “please make your science good before you publish in the WAPO”

Have a great one.

"What’s your point? You have merely pointed out that methane CAN be a solute at higher concentrations than the minimum O2 levels required to support aquatic life. Relevance?"

My point is simply that dissolved gaseous species, even though present at concentration levels of parts per million, can still be highly biologically significant.

And I'll say for the fifty-fifth time, I NEVER SAID METHANE WAS A PROBLEM. I don't see why you keep bringing that up.

"As an aside, you’ll note I prefer to employ a solubility number expressed in moles (micro moles actually) per litre, because comparing solubility by mass (mg) can be misleading due to the difference in molecular weight of 02 versus CH4.

One unit vs another. As a chemist, I certainly understand the "micro-moles/liter", but for the benefit of non-chemist lurkers/readers, I used the still valid but more easily understood figure of "mg/Liter", which is, even in the scientific literature, a more widely used and less confusing (to nonchemists) unit.

As to the rest of your suppositions, I'll wait 'til I have a chance to see the actual published peer-reviewed article over a newspaper summation. I'm quite well aware that, on subjects of science, reporters virtually always get one or more substantial points totally wrong.

On the overall subject of the Gulf oil spill, if you look back over my postings on the subject, you will see that I was one of the early advocates for NOT thinking "there's a spill in the Gulf, AND WE'RE ALL GONNA DIE".

Thus far, all the evidence points to my early comments as having been correct.

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