Submerged Players of Climate Change: Marine Viruses

While the world has been fixated on the usual players of global climate change, such as fossil fuels and deforestation, a group of unexpected contenders has emerged from the ocean depths – marine viruses. These small but powerful entities are now stealing the spotlight as scientists reveal their profound impact on our planet’s climate.

With an estimated army 10³⁰ virus particlesMarine viruses dominate the vast expanse of the ocean with their amazing diversity. All aquatic organisms are affected by their presence in one way or another – whether they are bacteria, algae, protists or fish. The jury is still out on whether the net effect of marine viruses on climate change is positive or negative. However, the mounting evidence is hard to ignore—marine viruses possess a transformative power capable of reshaping the fabric of the marine ecosystem—and their impact on biogeochemical cycles is anything but subtle.

Viral conversion: Unraveling the carbon cycle in the ocean

Phages (or simply phages) – viruses that infect bacteria – are the dominant viruses in the ocean. When infected, the phages cause their hapless bacterial hosts to explode through a process known as virolysis, thereby releasing nutrients and organic matter into the surrounding seawater. This phenomenon, known as viral conversiondiverts microbial biomass from secondary consumers in the food web, such as plankton and fish, to the pool of dissolved organic matter primarily consumed by heterotrophic bacteria.

When bacteria die and undergo decomposition, their organic matter has the potential to contribute to either the aggregate of particulate organic matter (POM) or dissolved organic matter (DOM). POM consists of complex structures and cannot be easily broken down by marine microbes. Hence, it is often transported to the deeper parts of the ocean. However, DOM is more digestible by microbes and thus incorporated into their biomass. As the microbial biomass in the ocean expands, it becomes a food source for organisms with higher trophic levels, including plankton, which in turn serve as prey for the fish.

But phages can also prey on these microbes. that it It is estimated that phages are killed About 10 to 20% of heterotrophic bacteria and 5 to 10% of autotrophic bacteria in the ocean daily, resulting in a significant release of carbon, nutrients and other trace elements into the microbial food web. The dissolved organic matter in turn leads to a bacterial feast as the microbes eagerly consume newly available nutrients and carbon, limiting their flow through higher trophic levels. Hence, viral decomposition enhances bacterial respiration which retains carbon in the oceans rather than releasing it into the atmosphere. In this way, phages help indirectly It sequesters nearly 3 gigatonnes of carbon annually.

Viral glycolysis: driving the nutrient cycle in marine microbes

Viral lysis also plays an important role in the release of other vital nutrients into the ocean microbial food web, such as nitrogen and phosphorus, which are encapsulated within bacterial cells in the form of nucleic acids and amino acids. These nutrient-rich compounds fuel growth and metabolic activities and serve as a valuable resource for both heterotrophic and autotrophic microbes.

Phages can also alter the carbon cycle by reshaping the metabolism in cyanobacteria, and they are one of the major players in global carbon dioxide.₂ stabilizing. For example, the researchers found that Blue infections infecting Synechococcus sp. Altering the photosynthesis of the host By maximizing energy production while inhibiting carbon dioxide₂ stabilizing. However, the broader implications of this phenomenon at the ecosystem level remain obscure, marking a critical area poised for future research.

Nightmares Boom: Virus Guardians in Action

Marine algae play a vital role in regulating carbon dioxide levels in the atmosphere through their photosynthetic prowess. However, problems lie in the depths when an abundance of marine algae appears. Enter the dreaded algal blooms, those uncontrollable explosions of algal growth in aquatic ecosystems. These blooms unleash a cascade of harmful effects on marine ecosystems, from oxygen depletion and food web disruption to the production of harmful toxins.

Once again, viruses take center stage. Lytic viruses that can infect marine algae play an important role in the demise of algal blooms It leads to an increase in dissolved organic matter which, again, fuels the growth of surrounding heterotrophic bacteria and restricts the flow of energy to higher trophic levels.

As a result, scientists are exploring the idea of ​​using viruses to naturally control and eliminate algal blooms. This exciting field of study is still in its infancy, and scientists are currently conducting small-scale pilot studies to gather more information and explore the potential of this approach. One example of this is the investigation of Heterosigma akashiwo virus (HaV), which has shown promising results in preventing recurrence of toxic red tides. caused by the harmful algal species Heterosigma akashiwo, which ultimately leads to fisheries protection. Another study indicates that A A mixture of viruses isolated from a natural lake reduced the abundance of the toxic cyanobacterium Microcystis aeruginosa In lab cultures by 95% in six days.

However, several challenges limit large-scale applications of viruses (and cyanophages) to control algal blooms. The dynamics of algal blooms in natural ecosystems are complex, and implementing viral interventions on a larger scale presents logistical and environmental challenges. Another big concern is the potential evolution of microbial resistance to viruses, similar to the way microbes develop resistance to antibiotics. Some potential solutions to overcome resistance are the use of a mixture of viruses, rather than a single lytic virus, and the engineering of viruses specific to the algae involved. Despite these limitations, the use of viruses to treat algal blooms shows promise and continues to be an active area of ​​research.

beyond the horizon

The role of marine viruses and bacteriophages in global climate change is still unfolding, and there is much more to discover. As scientists continue to delve deeper into this fascinating field, there are many future steps that show promise.

First and foremost, further research is needed to reveal the full range of viral diversity in the oceans, as well as the interactions between different viruses and microbial communities under different environmental conditions. Recently, scientists made a remarkable discovery regarding the existence of “superviruses” that possess unusually large genomes (ranging in size from 300-1000 kilobase pairs (kbp)) and infect ocean hosts. What makes these viruses more interesting is their detection very widespread It has the ability to infect a wide variety of eukaryotic hosts. However, the extent to which giant viruses affect marine ecosystems and biogeochemical processes remains largely unexplored, warranting further research.

In addition, understanding the mechanisms underlying virus-mediated nutrient recycling and carbon sequestration could pave the way for innovative approaches to mitigate algal blooms and enhance the efficiency of ocean carbon sequestration. Furthermore, incorporating viral dynamics into oceanographic models will help improve predictions of ecosystem responses to climate change.

With viruses becoming increasingly recognized as influencing agents in the oceans, further research into the roles and interactions of marine microorganisms will undoubtedly contribute to our ability to mitigate environmental challenges and enhance the health and resilience of marine ecosystems in the face of a changing world.