Ocean Microbes: How They May Directly Impact Climate Change

Ocean microbes may play an important role beneath the surface, but now new research shows that they are linked to processes in the atmosphere as well, and may even directly impact climate change.

A team of scientists from UC San Diego and the Scripps Institution of Oceanography reported in the journal ACS Central Science that the process by which marine bacteria consume phytoplankton has an apparent direct role in affecting cloud properties.

Phytoplankton are microorganisms that produce molecules that become airborne when they decay - that is, if bacteria don't eat the molecules first. As the bacteria feed, phytoplankton break down into component molecules, such as fats and lipids, which can become airborne as the ocean's surface churns. Once in the atmosphere, these so-called sea spray particles join dust and other particles, or aerosols, in becoming the framework for the drops of moisture that ultimately collect and form clouds.

Since cloud cover and precipitation are major contributors to Earth's climate, understanding the dynamics of clouds, and now ocean microbes, is crucial for creating more accurate climate simulations that attempt to replicate atmospheric phenomena.

"It is exciting to finally be able to find a connection between microbes in seawater and atmospheric sea spray," researcher Kimberly Prather, from the University of California (UC), San Diego, said in a statement. "These chemical changes ultimately affect the reflectivity of marine clouds and thus could have profound impacts on climate over a large portion of the planet."

During the study, scientists created a replica ocean in a controlled setting to observe the types of marine particles that contribute to cloud formation, and possibly human health issues once they become airborne. They did this by importing 13,000 liters (3,400 gallons) of natural seawater from the California coast into a 33-meter-long tank that mechanically generates waves.

The factors that control the transfer of chemicals from the ocean to the atmosphere in sea spray had, until now, remained a mystery. But using their recreation, the team sought to reveal which chemical components are transferred and when.

They found that variations in the specific ocean microbes affected the concentrations of less water-soluble molecules such as lipids in seawater. In turn, bursting bubbles from the waves launched these molecules into the atmosphere.

These new findings help shed light on the importance of the complex interactions between microbes in seawater and how they control the composition and cloud-forming ability of sea spray aerosol. For example, ocean microbes can influence cloud brightness, which in turn helps determine if solar energy is absorbed on Earth's surface or reflected away from it, and thus influences temperature.

This and other revelations will hopefully improve climate models in the future, as well as allow scientists to better understand the effect of aerosols on human health, as these compounds are inhaled by beachgoers and residents of coastal communities every day, and could have substantial effects.

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