The clouds over your head may have started around a seed made of a seashell. Microscopic algae called phytoplankton can affect the amount of clouds that form and even how they move.
One such species, Emiliana huxleyi 鈥� known as Ehux 鈥� is a single cell encased in overlapping lacy discs of calcium carbonate. When Ehux is infected with a virus known as EhV, the cell sheds its chalky exoskeleton. Sea spray can fling these frisbee-shaped scales into the air, where they can become the seeds around which air condenses into droplets.
鈥淲e wanted to see how microbial interactions may be reflected in the aerosol population, which can then affect clouds,鈥� says Miri Trainic at the Weizmann Institute of Science in Israel. She聽and her team tested the effect of the virus on the phytoplankton using two groups 鈥� one infected with EhV, and the other without. The virus is known to break down the phytoplankton鈥檚 outer shell.
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One day after viral infection, they saw the percentage of cells that still had an exoskeleton drop from 91 to 66. The uninfected group saw no decrease. By three days after infection, the concentration of calcite shells had increased three-fold.
Burst the bubble
Trainic and her colleagues also tested how these bits of shell might make their way into the air. They used a bubbling system to mimic sea spray in the tanks where both groups of phytoplankton were held.
As the bubbles burst at the surface, bits of shell were released into the air 鈥� but the amount released was 10 times higher for the infected group, because there was a higher concentration of that material in that tank.
The team also found that these exoskeleton shards may contribute more to cloud formation than sea salt because of their aerodynamic shape. Once they are flung into the air, they float back down about 25 times slower than the average sea salt particle.
That hang time gives the air more chance to condense around them, and also allows time for chemical processes to take place on the surface.
When calcium carbonate reacts with gaseous nitric acid in the atmosphere, it can create relatively large calcium nitrate particles that create haze droplets and can act as giant seeds around which clouds more quickly form.
鈥淒uring聽the North Atlantic spring bloom the water is filled with Ehux, and then comes the virus and infects it. That鈥檚 when you鈥檙e going to see this effect,鈥� Trainic says.
