Climate change impacts to be reduced by storing carbon on the ocean floor

A research team from Ohio State University (OSU) has discovered that storing carbon on the ocean floor may be possible after investigating RNA virus species.

Investigating 5,500 marine RNA virus species reveals an innovative solution for climate change

Researchers investigated the 5,500 marine RNA virus species recently identified and discovered that several of the species may contribute to an innovative solution for climate change. Scientists observed that this could be done by taking the carbon absorbed from the atmosphere and permanently storing carbon on the ocean floor.

Additionally, scientists observed that a small portion of these recently identified species had ‘stolen’ genes from organisms that they infected, which meant that researchers could identify their presumed hosts and their functions in marine processes.

Beyond mapping a source of foundational ecological data, the research leads to a deeper understanding of the outsized role these tiny particles play in the ocean ecosystem.

“The findings are important for model development and predicting what is happening with carbon in the correct direction and at the correct magnitude,” explained Ahmed Zayed, a research scientist in microbiology at OSU, and co-first author of the study.

Controllable ‘knobs’ for storing carbon on the ocean floor

The question of magnitude is a serious consideration when taking into account the vastness of the ocean. Matthew Sullivan, Professor of microbiology at OSU, and lead author of the study envisages that this research will contribute toward identifying viruses that, when engineered on a massive scale, could function as controllable ‘knobs’ on a biological pump that impacts storing carbon on the ocean floor.

“As humans put more carbon into the atmosphere, we are dependent on the massive buffering capacity of the ocean to slow climate change. We are growing more and more aware that we might need to tune the pump at the scale of the ocean,” said Sullivan.

“We would be interested in viruses that could tune toward a more digestible carbon, which allows the system to grow, produce bigger and bigger cells, and sink. And if it sinks, we gain another few hundred or a thousand years from the worst effects of climate change.

“I think society is basically counting on that kind of technological fix, but it is a complex foundational science problem to tease apart.”

An international effort to mitigate climate change

The RNA viruses investigated in this study were detected from plankton samples collected by the Tara Oceans Consortium. This is an ongoing global study aboard the schooner, Tara, dedicated to the investigation of the impact of climate change on the ocean. The international endeavour intends to dependably envisage how the ocean will respond to climate change by becoming acquainted with the mysterious organisms that live there and ensure most of the work by absorbing half the human-generated carbon in the atmosphere and producing half of the oxygen humankind breathes.

Researchers noted that while these marine viral species do not threaten human health, they do behave as all viruses do infecting another organism and utilising its cellular machinery to make copies of itself. The outcome could be considered bad for the host; however, a virus’ activities may benefit the environment – for example, helping dissipate a harmful algal bloom.

RNA virus species: Determining where they belong in the ecosystem

In order to define where the RNA virus species belong in the ecosystem, scientists developed computational techniques that coaxed information about the RNA viral functions and hosts from fragments of genomes that are, by genomics standards, small to begin with.

“We let the data be our guide,” said Guillermo Dominguez-Huerta, a former Postdoctoral Researcher in Sullivan’s lab, and co-author of the study.

Statistical analysis of 44,000 sequences revealed virus community structural patternsthe team utilised these patterns to assign RNA virus communities into four ecological zones: Arctic, Antarctic, Temperate and Tropical Epipelagic (closest to the surface, where photosynthesis occurs), and Temperate and Tropical Mesopelagic (200-1,000 metres deep). These zones closely match zone assignments for the approximate 200,000 marine DNA virus species that had been previously identified by researchers. 

The diversity of RNA viral species was higher than expected

Scientists encountered some surprises when conducting this analysis – though biodiversity tends to broaden in warmer regions close to the equator and drop close to the colder poles, Zayed observed that a network-based ecological interaction analysis demonstrated the diversity of RNA viral species was higher than expected in the Arctic and Antarctic.

“When it comes to diversity, viruses do not care about the temperature,” said Zayed. “There were more apparent interactions between viruses and cellular life in polar areas. That tells us the high diversity we are looking at in polar areas is basically because we have more viral species competing for the same host. We see fewer species of hosts but more viral species infecting the same hosts.”

To identify likely hosts, researchers tried several methodological approaches. They first inferred that the host based on the classification of the viruses in the context of the marine plankton. Then they made predictions established on how quantities of viruses and hosts ‘co-vary’ because their abundances depend on each other. The third strategy comprised of collecting evidence of integration of RNA viruses in cellular genomes.

“The viruses we are studying do not insert themselves into the host genome, but many get integrated into the genome by accident. When it happens, it is a clue about the host because if you find a virus signal within a host genome, it is because at some point the virus was inside the cell,” said Dominguez-Huerta.

Maximising the fabrication of viruses in the ocean

While a majority of dsDNA viruses had been discovered to infect bacteria and archaea, which are abundant in the ocean, this novel analysis revealed that RNA viruses primarily infect fungi and microbial eukaryotes and, to a lesser extent, invertebrates – a minimal fraction of the marine RNA viruses infect bacteria.

The analysis also revealed an unanticipated discovery of 72 discernible functionally dissimilar auxiliary metabolic genes (AMGs) sprinkled among 95 RNA viruses, which provided some of the superlative clues as to what kinds of organisms these viruses infect and what metabolic processes, they are attempting to reprogramme to maximise the fabrication of viruses in the ocean.

RNA virus species connected to carbon export

Furthermore, the additional network-based analysis discovered 1,243 RNA virus species connected to carbon export; conventionally, 11 were understood to be implicated in promoting the storing of carbon on the ocean floor. Two viruses linked to hosts in the algae family were designated as the most promising targets for further research.

“Modelling is getting to the point where we can take bags of genes from these large-scale genomic surveys and paint metabolic maps,” concluded Sullivan, Professor of civil, environmental, and geodetic engineering, and Founding Director of Ohio State’s Centre of Microbiome Science.

“I am envisioning our use of AMGs and these viruses that are predicted to infect particular hosts to actually dial up those metabolic maps toward the carbon we need. It is through that metabolic activity that we probably need to act.”

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