Diatoms: they produce 20% of the earth's oxygen, but now they are dying. 03/26 Update SLTechnology News&Howtos

Diatoms: they produce 20% of the earth's oxygen, but now they are dying.

2025-03-26 Update From: SLTechnology News&Howtos shulou NAV: SLTechnology News&Howtos > IT Information >

Shulou(Shulou.com)11/24 Report--

The round, long and square ones in the picture are all diatoms (image source: Gordon T. Taylor, Stony Brook University / Public Domain). For most life on Earth, you have to breathe oxygen to survive. The vast majority of the oxygen we breathe now is biologically produced-such as plant photosynthesis. But the most important oxygen producers are not the trees we are familiar with, but the tiny creatures in the water, one of the most important groups of which is diatoms.

Diatoms are tiny single-celled algae, mostly only a few microns to dozens of microns long, and several can be placed on the tip of a needle. But if you look at these small creatures under a microscope, you will be shocked by their exquisite appearance-in fact, the exquisite structures you see are the cell walls of diatoms, also known as their "silicon shells".

Unlike plants or animals, the diatom shell under a 1500-fold microscope (image: Massimo brizzi / Wikipedia) is made of silica, hydrated silica, to be exact, the same composition as Opal (a gem). Similar to Opal's discoloration, the cell walls of diatoms also show brilliant structural colors.

The hard shell of Opal's surface (photo: Dpulitzer) makes diatoms the absolute winner on Earth. More than 20,000 species of diatoms are known to be found in oceans, rivers and lakes around the world. You can even find diatoms in hot springs or the Southern Ocean.

Such a wide distribution has also brought great productivity. It is estimated that an average of 20% to 30% of the oxygen in every breath you breathe is produced by diatoms. This number even far exceeds the tropical rainforest known as the "lungs of the earth". While producing oxygen, diatoms absorb large amounts of carbon dioxide from the environment and store it in the depths of the ocean.

"diatoms are one of the most important plankton in the ocean," explains Jan Taucher, a marine biologist at the GEOMAR Helmholtz Ocean Research Center. "any change in them could lead to a major shift in the ocean's food web and even change the ocean's ability to absorb carbon dioxide as a carbon sink."

Acidification of sea water what we all know is that climate change is threatening marine ecology. Carbon dioxide in the atmosphere dissolves into sea water, which increases the acidity of sea water. For marine creatures with carbonate shells (mainly calcium carbonate), this is almost a disaster: in acidified water, the process of building calcium carbonate shells consumes more energy; and if the acidification increases, carbonate concentrations fall too low, and their carbonate shells may even be dissolved-a disaster that corals and shellfish in many areas are experiencing.

As acidification intensifies, the carbonate shells of many marine organisms are under threat (photo: NOAA) however, for diatoms, the story of climate change is much more complicated. Many studies believe that diatoms theoretically have the ability to resist seawater acidification and may even benefit from climate change. On the one hand, as a kind of microorganism capable of photosynthesis, when the amount of carbon dioxide dissolved in seawater increases, diatoms absorb carbon dioxide more easily and increase the rate of photosynthesis. On the other hand, an acidic environment can reduce the dissolution rate of silicon dioxide, so diatoms can build their own "silicon huts" more easily.

The problem is that these are only theoretical speculations. Even single-celled algae have very complex life systems, and further research is needed to know the more specific and possible fate of diatoms under climate change. Recently, Taucher and colleagues found that previous discussions of diatoms often missed a key factor, which is likely to threaten the survival of diatoms.

For many plankton in the ocean, the concentration of major nutrients (such as nitrogen or iron) determines their distribution. But diatoms pay more attention to the silicon in seawater.

Silicate in sea water is generally unsaturated, so the shell of diatom is easy to be eroded and dissolved by sea water. When the diatom is alive, it secretes an organic coating outside the shell to provide protection. However, when the diatom dies, the protective coating will be degraded by the bacteria. In the process of the shell falling down to the depths of the ocean by gravity, the silicon in the shell is also released into the sea water "along the way", which partly makes up for the silicon consumed by diatoms in the surface water.

In this way, the diatom itself acts as a "biological pump", transporting the silicon in the seawater from the surface to the deep layer, and then transported back to the ocean surface by the global ocean circulation for the next batch of diatoms to use.

Microscopic diatoms shine like gems (photo: Watson & Sons) in order to simulate changes in the marine environment under climate change, Taucher's team adopted an enclosure experiment: they separated a piece of sea water from each of the five oceans and pumped it out artificially to maintain a normal seawater circulation. This is like intercepting five huge test tubes in the ocean, and researchers can inject different concentrations of carbon dioxide into the test tubes to simulate different degrees of ocean acidification.

In these five test tubes, the researchers simulated seawater acidification in medium emission scenarios (RCP 6.0) and high emission scenarios (no measures to control carbon emissions at all, RCP8.5). The results showed that the ratio of silicon to nitrogen in marine sediments increased by an average of 17%. In other words, in more acidic water, more siliceous shells fall into the sediment rather than dissolve into the sea water.

Further modeling of the domino of diatoms has brought greater concern. The distribution of silicon in seawater is mainly affected by "diatom pump" and marine circulation transport. However, in the case of serious acidification of the sea water, the dissolution rate of the shell slows down, and more diatom shells will sink directly to the seafloor and deposit there for a long time, which can not add enough silicon to the upper sea water. The ocean circulation obviously cannot fill this gap, so the diatoms that grow later will not be able to get enough silicon to make their own shells.

Acidification of sea water will lead to a significant reduction in silicate concentration in surface seawater (red represents increase, blue represents decrease, picture source: original paper) simulation results show that in high emission scenarios, the concentration of silicate in the ocean surface will decrease by about 27% in 2200, which will directly lead to a 26% reduction in the number of diatoms. If such a large number of primary producers are lost, other life on Earth will also be greatly affected.

In the paper, the researchers are more concerned that "the consequences of ecosystem function and the carbon cycle are more difficult to assess", and the current data do not discuss the domino effect on other consumers in the biological chain.

Source: Howard Lynk, but in any case, the findings warn us of how unnoticed feedback mechanisms in the Earth system can change our predictions of environmental and biological changes-we still don't know enough about how our planet and the life forms in it interact.

For Taucher, the discovery was a poignant surprise: "this surprise reminds us again and again that we will face incalculable risks if we do not deal with climate change quickly and decisively."

Friendly hint: you can breathe while reading.