Why We (should) Care about Methane in the Gulf of Mexico

(Just a note: The giveaway period for the audiobook of The Poisoner's Handbook has ended. If your comment is not published, it's too late to be considered for a free copy. But still glad to hear your ideas! Winners to be notified on Wednesday).

One of the most interesting - and I think important - comment threads on this blog has concerned risks posed by the gas methane, blamed (along with BP) for the devastating oil spill in April and still seeping into the water from the broken drill pipe.

"We don't know the composition of the crude oil as it is leaving the well head. This crude is reported to have a very high methane content," wrote one smart reader, noting that one of the greatest risks related to methane (composed, by the way, of one carbon atom to every four hydrogen atoms, CH4) is that as bacteria break it down, the metabolism process can involve sulfates in the water and lead to formation of the much more poisonous gas, hydrogen sulfide (two hydrogens for every one sulfur, H2S).

I was reminded of unanswered questions about methane while reading a recent piece in Newsweek entitled "What the Spill Will Kill" which reports that "Giant plumes of crude oil mixed with methane are sweeping the ocean depths with devastating consequences."

What devastating consequences exactly I wondered and did the presence of methane make a difference, in how the plumes formed, in how poisonous they were. But the article didn't answer those questions, partly because this is all one big chemical experiment and partly because methane in water lacks the obvious drama of poisonous chemical dispersants and toxic and visibly murderous crude oil.

But let's pay methane a little respect here. By all accounts, BP and its cohorts were remarkably careless in managing methane risks in their deep-sea drilling. It's common knowledge that where we find fossil fuel deposits be they coal mines (see earlier post, The Methane Calculation) or oil deposits, they're accompanied by methane which is primary component of "natural gas" (the user-friendly named coined by big energy companies.)

At the bottom of the Gulf of Mexico, at what we'll call BP oil spill depth, almost a mile down, a combination of high water pressure and low temperatures - reportedly hovering just above freezing, around 34 degrees fahrenheit - methane tends to form into ice-like crystalline structures, called methane hydrates or clathrates. You may remember that this icy version of methane stymied one of BP's first efforts to put a containment dome over the leaking riser pipe. By the way, the oil industry is now working to mine methyl hydrates, which change into gaseous methane as they rise, warm, and depressurize, and harness them for energy.

One of the theories of the BP disaster is that a chemical reaction, perhaps triggered by the compounds used for sealing cement around the drill hole, caused rapid heating, converting hydrates to a soaring building up gas, which rocketed up the pipe to the rig. Methane being highly flammable - as anyone owning a gas stove knows - was ignited by sparks coming off equipment off the rig, triggering the horrifying fiery explosion that followed.

But back to the bottom. At depth, the Gulf of Mexico is unusually rich in methyl hydrates, so much so that it supports a flourishing community of methanotrophs or methanophiles- methane-digesting bacteria - and also a community of very strange creatures called ice worms that live on the bacteria.

Which is another way of letting us know that there's a lot of methane down there. In fact, by some accounts the hydrocarbons pouring out of the BP leak (yes, I do enjoy making that connection) are about 60 percent crude oil and 40 percent methane. In fact, so much methane has been pouring into the gulf - by one estimate a million times more than from the natural seepage - that scientists are now preparing to measure the extent of the spill's reach - those underwater plumes, in fact, by tracking methane.

Very handy, you might say. But the more interesting point is that the scientists tracking these plumes believe that their massive spread underwater is largely being driven by the methane component in this leak. To quote the Gulf Oil Blog of the University of Georgia Department of Marine Sciences: "Think of it as gas-saturated oil that has been shot out of a deep sea cannon under intense pressure - it's like putting olive oil in a spray can, pressurizing it and pushing the spray button. What comes out when you push that button? A mist of olive oil. This well is leaking a mist of oil that is settling out in the deep sea."

There are also those who believe that an excess of methane in water is poisonous to fish. Part of this argument is that fish are designed to take in dissolved gases through their gills, making methane fairly insidious. There's some evidence that shows that high concentrations of methane are harmful to the nervous system and circulatory system of many fish species. To be fair, not everyone considers this a serious problem; methane is not the most reactive of gases in terms of toxicity.

But it all adds up to a reminder that this isn't just an "oil" spill. It isn't just about what we see. It's also about what we don't see. And the time to acknowledge that - and here's an idea, actually try to do something about it - happens to be now. That would be: NOW.


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I find it unlikely that methane at any plausible concentration in the environment is toxic to fish, and certainly the very questionable link you cite doesn't show that. Toxicologically, methane is classified as a simple asphyxiant.

Methane is actually rather inert, chemically speaking.

I would imagine that fish get more people invested in the story, but the real story is how this massive amount of methane will impact the bacterial consortia in the oceans that do the grunt work of balancing out the mineral pathways that the whole complex ecosystem uses to survive. H2S is poisonous to us I suppose, but to some microbes it is their lifeblood.

Eventually, life will win out. It's a drastic event and things won't be the same - that's for sure. But I look to the recent NOVA program and Science News cover story on Mt. St. Helens and know that whatever seems beyond repair in nature will end up surprising us.

But when I hear dire consequences being projected by my fellow scientists, I have to wonder about the humility involved in those leading the cry. How many experiments have confounded them? And if they are so sure of certain things happening in the future, how much science do they really think they know?

Did your smart reader point out that H2S is often consumed right away by sulfur oxidzing microbes and that this whole reaction is dependent upon sulfate concentrations?

If anything can clean this up - its microbial communities. Who are we to doubt them - they have survived on this Earth for billions of years. The oldest known living things.

So I guess my question is - if you were in charge right now what would you do exactly?

By intricatenick (not verified) on 07 Jun 2010 #permalink

And the methane that does get to the surface will add to climate warming.
One sign that the recent capping was working is the methane flaring from the recovery rig. Which leads me to wonder whether there is a good method of recovering methane rather than just burning it. And a *lot* of methane does get flared. These flares are the most obvious points of light according to pi8ctures from space.

By natural cynic (not verified) on 07 Jun 2010 #permalink


Methane may be inert in most systems but is the KEY component in the carbon cycling of the underwater ecosystem. Anaerobic methane oxidation and its partner methanogenesis forms the absolute bottom of the food chain in marine environments. If Venter and his group ever publish their shotgun sequencing of the ocean we may get better vision of the more detailed metagenomic look at these consortia, but the genetic mechanisms found to date are incredibly complex.

If you are sure that the reference makes methane non-toxic for fish I doubt that the microbial enhanced depletion of oxygen in aerobic methane oxidation will make easy for the fish to breathe. I guess there is more than one way for methane to become an asphyxiant. Try a complex asphyxiant...

By intricatenick (not verified) on 07 Jun 2010 #permalink

Good question and wouldn't it be great to have the solve-all answer? Here's what I wouldn't do - waste time trying to convince the public that underwater plumes couldn't possibly exist. Here's what I would do - if I had BP's deep pockets, anyway - put some serious money toward a comprehensive and detailed study of the undersea spread of oil and do it now. I'd want thoroughly researched answers to all these troubling questions. And I'd share every answer in the most transparent way so that other smart scientists could build on the research. Would this have immediate benefits - probably not. Would we learn a lot more than we're likely to do otherwise - probably yes. And would I - Ms. In Charge of It All - have no credibility than if I spent my time denying that any problem existed whatsoever. For that, a simple yes.

I posted something but it had two links and didn't make it. I will try dividing it in two and see if it does.

Methane is probably not that toxic. The greatest danger to wildlife is almost certainly the loss of O2 as methane is metabolized. It takes two molecules of O2 per molecule to oxidize one of methane. Methane and O2 have just about the same solubility in water, and it increases with depth. Unfortunately the O2 level of sea water is set at the surface at 1 atmosphere. The methane concentration is determined by the depth at which the methane dissolved, so the methane levels can be many times the O2 level.

Many fish have what is called a gas gland, where they can extract gas from the water and put it in their swim bladder for buoyancy. They concentrate all gases from the ambient level in sea water to pure gas at the pressure at depth. They can develop very high pressures of gas in their gas glands. In a methane environment, they would concentrate methane along with O2. They would also concentrate trace inert gases which would be an excellent tracer, confirming that the fish were exposed to the plume.


Marine mammals do not have a gas gland, so they are only able to remove gases from their blood when they exchange air at the surface. Partially soluble gases like methane will be much more difficult for marine mammals to get rid of because blood will only hold so much at 1 atmosphere when the mammal is on the surface breathing. I suspect that marine mammals beach themselves when they get bubbles of gas in their bodies/blood stream or gut. This gas may come from the gas bladders of the fish they eat, or from bacterial action in the marine mammal gut. In some of the pictures from marine mammals stranding, the livers are full of bubbles (the liver gets blood from the gut and so bubbles would be trapped there).


When there are marine mammal strandings, they should look at the composition of the gas in any bubbles in the liver. I suspect these will be methane. There may even be helium and other inert gases with the same isotopic ratios as what is coming out of BP's leak. Those isotope ratios might be preserved in gas concentrated by fish gas glands. That would be an excellent way to track the extent of the plumes and to implicate BP for the marine mammal strandings when they occur.

... rich in methyl hydrates, so much so that it supports a flourishing community of methanogens - methane-digesting bacteria...

Not that it really matters for the context of this post, but methanogens are the archaea that produced the methane in the first place ( from genesis meaning origin). Methyltrophs are the bacteria that eat methane. [/pedantry]

A really good catch, in my opinion. Thanks so much - it's fixed.

Just finished The Poisoner's Handbook and it was great! I was fascinated and educated, by both the science and history, and your storytelling and writing style made it a very compelling read. As scary as death by cyanide sounds, I found the Radium poisoning to be most disturbing. A creeping, insidious, disintegrative death by something associated with discovery, vitality, and even fun.

Thanks so much. And I agree with you about radium. It's one of the great cautionary tales in science, the embracing of a discovery as something miraculous, the gradual realization that what makes it so powerful also makes it deadly.

As someone who has taught inorganic and biochemistry for 30+ years:
In the 2nd paragraph, the writer claims that the breakdown of methane can produce H2S. I know of no such reaction, and it is certainly impossible without a plausible source of sulfur. As others have noted, methane is remarkably inert chemically, except for its tendency to burn in oxygen to produce CO2.

By EnergyMan (not verified) on 08 Jun 2010 #permalink

Thanks for a reminder that I needed to state that a lot more clearly. You'll see I've tweaked it in the piece, based on my understanding that as bacteria (methanophiles) breakdown methane, they may use sulfates in the water to help with digestion of the hydrocarbons.. It's a byproduct of that process that may create hydrogen sulfide.

Boy, I've been way too chatty about this post. But this very smart interview on the Rachel Maddow show:


reminded me of a point I didn't raise in my post, which follows on the hydrogen sulfide discussion. Methane-digesting bacteria use sulfates but also consume a lot of oxygen during the breakdown process. Which means they deplete oxygen levels in the water. Which, as dicussed in the interview, is also a significant threat to aquatic life.

Energy man, sea water has 910 ppm sulfur as sulfate. When bacteria oxidize methane, first they consume all the O2, then the nitrate, and then the sulfate. When they do that they produce H2S.

good points made in posts but no discussion on dilution in the water column, sea currents, and the shear volume of sea water in the gulf vs the well output. Any thoughts on this and the actual long-term effects. i.e. we as humans drink low concentrations of chorine and fluoride in water every day. Also regarding sulfur i believe crude itself contains high concentrations of sulfur.

Seawater has about 0.22 moles of O2 per cubic meter. That is 7753 ton /km3. There are reports that the spill is leaking about 1 million gallon per day. That is ~3500 tons per day, which takes ~ 14,000 tons of O2 to metabolize, or about the O2 in 2 km3 of sea water. The leak has been going for ~50 days, that is enough to remove 100% of the O2 from about 100 km3 of sea water.

Rendering 100 km3 of sea water devoid of O2 is pretty serious, no multi-cellular organism can live where there is no O2.

Oil and gas seeps are natural events and, occasionally, leave behind massive tar sands deposits such as those mined Athabaska. The billions of barrels of liquids and gases released into the environment hasn't sterilized the earth yet. However; sugar, fats and alcohols, sold to humans for comfort food kill millions annually. Why not fight to eliminate those disasters, and leave poor 'ol BP alone.

By Irvin Nielsen (not verified) on 14 Aug 2010 #permalink