'Ocean-in-a-lab' shows the power of tiny climate change fighters

The ocean is incomprehensibly vast, spanning most of the planet. To examine the effect of the five ocean basins on the climate, however, researchers had to shrink the seas — allowing for the study of some of the tiniest climate change fighters, microbes.

Scientists from the University of California, San Diego created an "ocean-in-a lab" to replicate and experiment with the ocean's conditions, including studying the ocean's microbial communities and how they affect sea spray.

Sea spray is crucial to cloud formation — without it, we wouldn't have clouds. Sea spray aerosols also directly affect the chemical composition of the atmosphere. Within the sea spray are the gases and aerosols spit out by the ocean's microbes.

A team of oceanographers studied how those expulsions interact with air pollutants from humans. A better understanding of atmosphere-forming ocean chemistry could eventually help humans hack the system, and curb climate change, the researchers argue.

In a presentation Monday at a virtual meeting of the American Chemical Society, Kimberly Prather, a USCD professor and the project's principal investigator, announced that ocean microbes have the potential to influence atmospheric composition, cloud formation, and weather. This research is not yet published.

Ocean-in-a-lab — Some scientists refer to the ocean as a “planetary thermostat” because of its significant effect on Earth's atmosphere. The color of clouds, for instance, can alter temperature: Brighter, whiter clouds keep things cool, while darker, gray clouds mean hotter weather.

For decades, researchers have hypothesized that phytoplankton determines the composition of clouds over the ocean, Prather explained. But those complex mechanisms are difficult to study in nature.

So Prather's team took the ocean to their lab, using seawater and creating waves that mimic the ocean's chemical, physical, and biological complexity.

The researchers set up a large tank similar to a 108-foot wave pool and filled it with thousands of gallons of seawater. Then, they tested out different compositions of microbes — phytoplankton, bacteria, viruses — as well as various levels of VOCs, or volatile organic compounds, spiking the water with nutrients to make the microbes flourish.

VOCs are environmental pollutants that come from sources including gasoline, household products like adhesives and paints, preservatives, and cigarettes. They can have a negatives effect on human health, potentially prompting eye and throat irritation, headaches, respiratory problems. They can also, as the this new study suggests, have an effect on climate change.

The research team measured how factors in the ocean and atmosphere ultimately affect the components of sea spray, including pH and aerosol size and shape. Those factors can change how clouds are formed, thus altering the climate.

In the future, humans could potentially tinker with that system in two ways:

• Changing the structure of the ocean's microbial communities
• Releasing air pollutants that react with sea spray in a specific way

Changes in the microbes themselves had a small effect, the team found. But increasing an atmospheric pollutant called hydroxyl radical had a larger impact on how clouds are formed. The chemical is produced naturally but can exist in higher concentrations in a polluted atmosphere. Since the gases from microbes reacting with the atmosphere ultimately had a bigger effect on clouds, the new findings suggest potential for scientists adding compounds to the atmosphere to change cloud formation.

The research could, in turn, be an entry point into altering cloud composition and hacking climate change. The project, the authors write in the to-be-published paper, could help to "unravel the impact of humans on the ocean's ability to control climate."

Abstract: Covering 71% of the Earth, the oceans represent a significant source of gases and aerosol particles to our atmosphere. Biological processes in the ocean produce chemical species which can profoundly alter the composition of the atmosphere. Once in the atmosphere, these species can undergo photochemical and chemical reactions which modify their ability to form clouds and impact climate. In the summer of 2019, the NSF Center for Aerosol Impacts on Chemistry of the Environment (CAICE) conducted the Sea Spray Chemistry And Particle Evolution project, or SeaSCAPE, a unique ocean-in-the laboratory experiment which focused on unraveling complex ocean-atmosphere interactions. The focus of the project involves developing a better understanding of how human pollution interacts and reacts with ocean emissions of gases and aerosols - and ultimately affects cloud formation, air quality, and climate. In a 33 m long wave channel filled with 3,400 gallons of seawater, sea spray aerosols and volatile organic carbon gases (VOCs) were continuously measured over the lifecycle of a phytoplankton bloom. Oxidative flow reactors were utilized to simulate different amounts of atmospheric aging of both nascent sea spray aerosols (SSA) and VOCs. The resulting aged SSA and newly formed secondary marine aerosol (SMA) were investigated using a broad suite of complementary on-line and off-line measurements of aerosol number, size, and composition. In addition, other properties including morphology, hygroscopicity, IN activity, phase state, enzymatic activity, and pH were measured. To link changes in the chemistry of the airborne species with seawater biological processes, seawater measurements were made to track the progression of the microbial communities to account for and explain the turnover of organic and inorganic species. As a whole, the SeaSCAPE experiment focuses on capturing how much and how rapidly atmospheric reactions transform ocean-derived biogenic emissions in an effort to unravel the impact of humans on the ocean's ability to control climate.