Where does the carbon in the ocean go?

Almost every creature, large enough to spray blue whales, and small to microbes, uses carbon in some way. But in the deep ocean, all the carbon is inequity.

Although some forms of carbon, such as sugar and protein, will soon be phagocytic by microbes, other forms, such as the fish scales and the chitin found in the marine exoskeleton, are difficult to consume. Scientists have long thought that this so-called refractory carbon is rarely eaten. Most of them are only combined with sediment on the seabed, while some so-called refractory molecules are suspended in the ocean and floated with water for thousands of years.

Now, a group of researchers have shown that the underground aquifers along the middle ridge of the ocean, like natural biological reactors, attract cold, oxygen - containing seawater to make microorganisms more difficult to decompose carbon and carbon, which is only part of the science. Peter Gregis (Peter Girguis) is a professor of organizational biology and evolutionary biology, who co led the research with researcher Sunny Shah Walter (Suni Shah Walter). The study was published in Nature Geoscience in April 23rd.

"It's possible to rebuild the way we know the deep-sea carbon cycle," says gagis. "It is different from building a small reactor in the laboratory, using 10 liters of water to pump water to get some results; this is a natural laboratory. At the end of the day, our organization wants to know what happened to carbon, we know it is produced by photosynthetic algae, knowing that fish will eat some carbon, and that some of the carbon is sinking. We can explain this, but there are some loopholes in the budget which make it impossible for us to draw accurate conclusions.

Although this research has begun to narrow these gaps, it has also helped to clarify part of the deep sea carbon cycle - which has been a mystery.

Shah Walter said, "we don't know where all the carbon goes before, and later we find that the underground aquifer is part of the answer. Most of the fluids that flow through the earth's crust may be like this, but we didn't know much about them before.

Michael Siraki (Michael Sieracki), director of the Marine Science Division of the National Science Foundation, said: "this study shows that the microbiological community can feed on the sea water that circulate through the deep sea crust. It was the Ministry of marine science that funded the study. "In turn, these microorganisms change the composition of the sea water and then return to the ocean."

The core of the system is the middle ridge of the sea, which is a huge chain of submarine mountains that surround the world. As a key part of the development of the tectonic theory, the ridge is like a convective monomer (convection cell), which permeates the cracks on both sides of the mountains, and when it is close to the earth's axis, it will be heated, where the magma is close to the surface. When the heated water rises, the cold oxygen water is pulled into the rock, forming a huge aquifer.

For scientists who are committed to understanding the carbon cycle of the ocean, aquifers are rare opportunities to study oceans in almost ideal conditions. "Our understanding of the direction of carbon in the ocean is very fundamental," he said. This gives us the opportunity to go to this natural laboratory for the first time. Measure at A point and measure at B point, and discuss some activities between them. "

In 2011, an international research group drilled a series of wells on the seabed of a site in central the Atlantic. They named it "North Pond" to collect water samples to determine which microorganisms were habitats in aquifers and whether they had the ability to consume carbon.

According to Shah Walter, scientists were surprised by their findings. "When the team extracted liquid from aquifer, they did not expect it to be similar to that of seawater," he said. All plans are for fluids that look more like other hydrothermal fluids. " It can show high levels of methane and low levels of oxygen.

For example, they are ready to measure methane. But at first glance, the fluid of "North Pond" looks very similar chemically to the sea, so I was attracted at that time, because my work was concentrated on the open ocean. Therefore, this is a unique environment where we can make use of this natural incubator. After the samples came out, we understood this. "

Although he and his colleagues have shown that microbes in aquifers can consume carbon, they still do not know how active they are.

"Based on the current limited data, we have been able to prove that water is entered with a certain concentration of oxygen, and when it falls, the carbon will fall directly down the ground," said gill. This makes us very confident that microbes are consuming carbon and using oxygen. "

In a subsequent test, gill and his colleagues found that, over a thousand years, as water flows through the aquifer, the carbon that is easy to eat will soon be consumed in just a few hundred years. More importantly, they found signs that the refractory carbon was also eaten.

He added: "what is exciting is that for a long time and even today, people are debating the speed of the degradation of carbon. But this natural laboratory not only shows us the biodegradation of carbon, but also the time it takes to eat. "

Finally, Mr gegis said that the study emphasized how to understand the depth of the ocean, so as to better understand the ocean.

"We believe that the entire ocean will pass through the mid ocean ridge system every 100 thousand to 200 thousand years," gagis said. "If the whole ocean is circulate through this aquifer, we think it may be the best representative of the typical microorganism, the sea water interaction, because it will pass through the system."

"Before we get these data, we have a big gap in cognition," he added. "We thought that water was pulled in here, and all the processes took place during heating. But we think that's no longer true, especially because these organisms are eating this unedible carbon. "

Reading the original text:https://news.harvard.edu/gazette/story/2018/05/deep-sea-natural-lab-a-rare-opportunity-harvard-researcher-says/