Methane in the Future
The Black Sea however is different. There the consortium is the basis for the food chain. The mats located on the ocean floor and the covering the chimneys arise from a thick layer of methane-eating archaea and sulfate-reducing bacteria. The carbonate cores that form the high sea chimneys are a by-product of the microbes’ metabolism. Huge layers of carbonate exist at Hydrate Ridge. A web of microscopic tunnels enables water to circulate through the chimneys and supplying the microbes with the nutrients they need.
If these microorganisms did not exist all the methane that is now being converted to carbonate and biomass would instead be emerging everywhere over the seafloor. Hinrichs and Boetius have estimated that an additional 300 million tons a year of methane would escape from the mud. It is not completely known how greenhouse gases emerging from the world’s large bodies of water will affect the planet. Certainly it would be much warmer.
Boetius says: “Everybody knows that our planet would be a different planet if there weren’t any plants. But nobody has thought about who keeps us from having a methane atmosphere.”
In today’s world humans are warming the planet by spewing carbon dioxide and methane into the atmosphere. There are methane-generating archaea in our rice paddies, as an example and in the intestines of cows. Euan Nisbet, a geologist at the University of London, says that the Arctic, where the warming is expected to be strongest is at great risk on land and in shallow seas there are hydrates that are stabilized mostly by low temperatures rather than by high pressures. Nisbet says the methane there “would probably take some decades or centuries to come out. But once it started, it would be essentially unstoppable.”
Scientists and researchers are not sounding alarms but the consensus is that it is important to understand how carbon cycles through our planet. Dickens says the early research concentrated on the beds of the oceans not below them. But it is now known that Archaea deep in the mud converts carbon into methane where it is stored in huge frozen reservoirs. Some of it leaks back into our ocean and ultimately into our atmosphere. The reservoirs are not static but are in a state of constant change. Dickens says they are always changing as he says like “electric capacitors” or familiar carbon reservoirs.
Dickens says: “It’s almost like you’ve got to think of them like forests where you have photosynthesis and respiration and trees growing and expanding and dying—there’s always this carbon turnover through the biomass. Well, it’s the exact same sort of thing. It’s this big carbon storehouse, but it’s all in methane, and it’s all controlled by the microbes.”
Microbes living under the seafloor have survived the movement of tectonic plates, formations of oceans and declining ocean masses. They have been buried, frozen in hydrate and perhaps exploded from a mud volcano. This cycle has been repeated over and over for billions of years. Long before other life forms evolved they have been thriving through the ages deep in the sediments of the earth’s oceans. Given that we know about global climate change it is critical that we understand all of the risk factors for our planet.
