Natural lumps of metal emit oxygen in the dark depths of the ocean, in the absence of photosynthesis, until now it was believed that there was no oxygen production in them at all
study recently published discovered that lumps of metal on the bottom of the sea emit oxygen into their surroundings. Until now, scientists believed that all the oxygen in the deep sea came from the air and the shallow water, and it was created by plants and algae performing photosynthesis. It has now been discovered that oxygen is also produced in the depths of the ocean itself, and not only reaches them from the surface of the water or from the layers close to it. Although the amount of oxygen obtained in this way is relatively small, it is a constant supply that may help the ecosystems in these areas.
Following the source of the oxygen
The surprising research was conducted both in the laboratory and in the field, using square cells containing measuring equipment. The researchers lowered these cells to the bottom of the Pacific Ocean, allowed seawater to flow into them and thus created a separation in the field between the measured substance and the environment, that is, conditions similar to controlled laboratory conditions. Using the equipment in the cells, the researchers measured various factors in the deep water, such as oxygen levels, temperatures and the presence of microorganisms. The research findings were recently published in the journal Nature Geosciences. The team of researchers showed that lumps of metal that are naturally found on the seabed, and that contain valuable minerals, emit oxygen into their surroundings. These polymetallic nodules, called polymetallic nodules or manganese nodules, were first identified in the region of the Pacific Ocean between Hawaii and Mexico.
The research team was headed by Prof. Andrew Sweetman, who specialized in the study of ecosystems in the depths of the Pacific Ocean. Sweetman and his partners studied extensive areas of the sea floor covered with those metal blocks rich in minerals. The sensors that measure the amount of oxygen have repeatedly indicated an unexpected phenomenon: the oxygen in the depths of the sea is not only consumed by organisms, as expected, but also produced and emitted in the depths. The researchers initially thought the readings were wrong, recalibrated the sensors and changed the sensitivity threshold of the measurement, but the same "abnormalities" in the oxygen level continued to appear.
The team members were still skeptical, and conducted a series of experiments to rule out the possibility that the measured oxygen was coming from bubbles trapped in their instruments or from components of the research equipment, but these possibilities were ruled out after thorough testing. Laboratory experiments conducted under conditions that mimic the environment in the depths of the ocean confirmed that dissolved oxygen levels in the water increase in the presence of the nodules.
"That was the point where we said, 'God, we have another source of oxygen,'" Sweetman said to ScienceNews. Sweetman added that the production of oxygen probably takes place on the surface of the blocks, as evidenced by the correspondence between the rate of oxygen production and the average surface area of the blocks.
Oxygen and hydrogen: both together and each separately
How do the metal blocks produce oxygen? The researchers discovered that the nodules act as tiny batteries, producing a voltage of 0.95 volts between several points on the nodules' surface. The voltage is similar to that of a normal AA battery, and probably causes the breakdown of water molecules into hydrogen and oxygen. Indeed, the playing blocks, which were nicknamed "Rock batteries", contain high rates of metals used to make batteries, such as copper, manganese and cobalt.
Decomposing water into oxygen and hydrogen is a well-known and common process. all water molecule Made up of two hydrogen atoms bound to an oxygen atom in covalent bonds, that is, by sharing electrons between the atoms. The water molecules can be broken down into hydrogen molecules and oxygen molecules when an electric current is applied to them in a process called electrolysis. Admittedly, electrolysis of seawater usually requires a voltage of at least 1.5 volts, but the researchers estimate that under certain conditions, groups of blocks can together produce a higher voltage. The oxygen produced in the process was called "dark oxygen", that is, oxygen produced in a process that does not require light, as opposed to photosynthesis - the process carried out by plants and algae, for which light is the energy that drives it.
The emission of oxygen from the metal blocks may explain why more than half of the biodiversity in these ecosystems grows on the hard surfaces of these blocks. However, it remains to be seen how dependent these organisms are on the oxygen emitted by the metals.
Economic interests in the depths of the sea
Mining companies are already eyeing these metal nuggets, which contain rare metals that have many technological uses. But mining in the depths of the sea may affect not only the area where the blocks will be collected, but also the wider environment: mining will raise clouds of dust that will settle over large areas, as happens near construction sites on land. At this stage, it is still unclear the extent of the ecological damage that will be caused as a result. More than that: beyond the direct influence of the blocks on their local environment, the study of these unique systems is important in other respects. The revealed mechanism expands our understanding of the processes of oxygen production on Earth, and even invites a rethinking of theories dealing with the origin of life on Earth.
To the website of the Davidson Institute, the educational arm of the Weizmann Institute
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