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Research ship "Tara" in Hong Kong: exact mechanisms still unknown
Photo: UCG / UCG/Universal Images Group / Getty Images
Not only humans are affected by viruses.
They also buzz around in nature.
However, science does not yet know much about these tiny organic structures.
A major global expedition on the French research ship Tara was to change that.
An international research team took water samples from all over the world.
The scientists presented the first results two months ago in the journal Science: Thousands of previously unknown RNA viruses that live in the sea.
The team is now describing some of the special properties of these viruses in another “Science” study.
Many of them therefore influence the global carbon cycle - and thus also the earth's climate.
So far, marine research has focused on DNA viruses, the team writes.
Their genetic material consists of deoxyribonucleic acid (DNA) – similar to that of plants and animals.
Known DNA viruses include adenoviruses, herpesviruses and smallpox viruses.
In contrast, the genome of RNA viruses consists of rinonucleic acid (RNA).
Examples of disease-causing agents include the Covid pathogen Sars-CoV-2, measles and Ebola viruses.
Very little is known about the RNA viruses that live in the sea, writes the team led by Matthew Sullivan from the Ohio State University in Columbus.
During the expedition with the research ship, the Tara Ocean Foundation discovered more than 5,500 previously unknown oceanic RNA viruses.
In the current work, the researchers are now presenting further findings on the viruses, which are primarily based on genetic analyses.
According to this, the oceanic virus species can be divided according to only four distribution areas: the Arctic, the Antarctic, the areas with a temperate and tropical climate near the water surface and areas with a temperate and tropical climate at a depth of 200 to 1000 meters.
phytoplankton as host
Unlike in most living things, the diversity of RNA viruses in the polar regions is surprisingly large.
From this, the team deduces, among other things, that many virus species have the same hosts here.
"We see fewer types of hosts, but more types of viruses infecting the same hosts," says co-author Ahmed Zayed.
In terms of hosts, the group focused on phytoplankton, which form the basis of the food chain and are also heavily involved in storing carbon dioxide (CO₂) from the atmosphere – the so-called biological carbon pump.
Because during the photosynthesis of the phytoplankton, the organisms store carbon as biomass while absorbing CO₂.
When the organisms sink to the sea floor after they die, the stored carbon can sometimes last for centuries.
For these periods it is withdrawn from the atmosphere.
Genomic analyzes indicate that oceanic RNA viruses strongly influence the metabolism of their hosts, especially plankton and invertebrates.
Since these organisms are involved in carbon turnover, the team suspects that RNA viruses have a central influence on the global carbon cycle.
A total of 1243 of the RNA viruses found intervene in such networks.
The connection was particularly clear in eleven species that use specific groups of algae – chlorophytes and haptophytes – as hosts.
"These algae are considered to be crucial components of the biological carbon pump," writes the team.
However, the exact role of RNA viruses in the oceans and the carbon cycle still needs to be clarified.
The oceans play an important role in storing CO₂.
The oceans absorb about thirty percent of the carbon dioxide emitted and store it in the form of carbonic acid.
This makes the world's oceans the largest reservoir on earth and acts as a buffer against climate change - without it, the current rise in temperature would be even greater.
However, this effect also has negative consequences: with increasing CO2 emissions, the oceans become more acidic and their pH value drops.
This has an impact on marine life such as mussels or corals, which are in danger of dying off.
dpa/joe