Why?

COVID-19 transformed the consciousness of humanity and how we think about viruses. The last comparable pandemic to COVID-19 was the Spanish flu more than a century ago. The current pandemic has demonstrated the harm that viruses impart, infecting as many as 400 million and causing more than 5.8 million deaths worldwide.

As we struggled to combat and contextualize this pandemic, it’s become easy to overlook the fact that viruses don’t just impact humans. Viruses are by far the most abundant entities on Earth and are key players in ecosystems on land and in the air and oceans.

Virus infections exert a powerful and persistent pressure on Earth’s biological organisms and ecosystems. Viruses are the smallest and the most pervasive entities in biology. They have a highly specific interaction and exert a persistent grip on their hosts. Ultimately, these interactions critically impact the entire ‘Earth system’ in ways we don’t yet completely understand.

In the oceans, microscopic organisms called phytoplankton are constantly under attack by viruses, frequently experiencing their own versions of pandemics. Phytoplankton are responsible for nearly half the oxygen on the planet by performing photosynthesis. Every day, trillions of these tiny plants grow and divide in every part of the global ocean. And every day, they are infected by viruses.

Oceanic “pandemics” happen on weekly time scales, causing phytoplankton populations to wax and wane over cycles that are currently hard to predict. These widespread infections exert a profound impact on Earth’s carbon cycle. They can determine the fate of carbon and whether it is transported to the deep ocean via large, rapidly sinking particles and sequestered for hundreds to thousands of years – or whether it is retained in the surface ocean by exploding cells and preventing particle formation, thereby making it more available for respiration and exchange with the atmosphere as CO₂.

Collectively, viruses influence the capability of the oceans to adsorb CO₂ in the face of climate change. Their impact is particularly relevant to phytoplankton that synthesize hard, heavy biomineral skeletons, such as calcium carbonate and silica, both of which are denser than seawater and effectively ballast carbon and facilitate its sinking to the deep ocean. And viruses can enhance it even further.

Viruses also appear to fundamentally impact cellular and ecosystem interactions in other types of phytoplankton to more broadly induce particle formation and export in ways we can’t yet predict or quantify. However, it’s clear that an infected cell, known as a “virocell,” has a powerful hold over the fate of a cell, its ecosystem and elemental cycling.

Viruses may even have direct impacts on feedbacks within Earth’s climate system. With 10 million viruses per drop of seawater, oceanic viruses are routinely incorporated into aerosols via frequent wind-driven turbulence and storms. Once airborne, they have the ability to ride regional and global wind patterns, and some even possess an innate ability to nucleate clouds, which increases Earth’s ability to reflect the sun’s energy back into space.

Processes that impact Earth’s reflectivity are precisely those being considered for geoengineering strategies, but we still don’t adequately understand the manner and degree to which microbes, like viruses, regulate and respond to a changing climate. These are fundamental gaps in our knowledge and predictive capability. After all, we live in a microbial world with microbes occupying every conceivable niche and having by far the longest collective evolutionary history – at least 3.5 billion years.

The “arms races” that rage between viruses and the planktonic cells they infect exert a fundamental control on Earth’s carbon cycle. And they have been doing so for at least hundreds of millions of years based on molecular and fossil evidence of biomineralizing phytoplankton in the oceans, long before humans appeared on the planet.

After years of rigorous and creative research, scientists are only now appreciating the essential roles, ways and outcomes of virus-cell interactions in the oceans, which take place in the micron scale but can regulate processes on a planetary scale.

To predict the impact of viruses on Earth’s carbon cycle and help combat climate change, it’s time for scientists to take action by evolving and changing the way they think and do science. They must converge scientific understanding across biological interactions, biomolecular and geochemical tracers, and microscale physics, with novel engineering and computational advances in a more transdisciplinary, holistic approach to solve this grand challenge. The good news is that a group of scientists from across the United States are already making strides in this direction.

Growing Convergence Research (GCR) represents the National Science Foundation’s Ten Big Ideas with an emphasis of the need for the sciences to practice such an integrated, transdisciplinary approach to science to solve a variety of challenges facing our planet and humanity.

With support from the GCR program, scientists from Rutgers University-New Brunswick, the Woods Hole Oceanographic Institution, Stanford University, the University of New Hampshire, the National Center for Atmospheric Research (NCAR) and the National Aeronautics and Space Agency (NASA) have entered into a new, interactive, transdisciplinary relationship. Their goal is to understand the convergent impact of marine viruses, biominerals, microscale physics and ecosystem interactions on phytoplankton carbon sequestration.

Participating scientists have already made some key discoveries, which have positioned them to solve this challenge. These include developing specific biomarkers to diagnose infection of phytoplankton at sea; documenting that actively infected phytoplankton cells clump together and sink into the deep ocean across the Atlantic Ocean; quantifying the amount of carbon fluxing from infected cells in sunlight surface waters to the deep ocean; characterizing the relationship of seasonal ocean mixing regimes with the extent of virus infection; and engineering a new way to track and characterize the vertical movement and biophysical properties of individual sinking particles on a hydrodynamic treadmill.

Critical discoveries are still to come including the role that ocean turbulence (via storms) plays in driving the extent of infection and the relative balance between the formation (aggregation) and destruction (disaggregation) of sinking particles as they transit to depth; the role that virus infection plays in coupling particle production with other ecosystem pathways; and developing the capability to predict the conditions under which virus-induced carbon export is maximal across the oceans.

After nearly five years of living through a pandemic, it’s time for the science community to broaden our gaze beyond the impact that viruses have on humanity and explore viral impacts on Earth’s oceans and carbon cycle.

The development of predictive models of ocean/climate patterns, behavior and responses requires a comprehensive and holistic, multidisciplinary understanding nationwide. Researchers are forming similar relationships to tackle other grand challenges and develop an unprecedented, predictive understanding across science. We hope this progress continues.