BY CAROLYN GRAMLING
When microscopic sea algae get sick,
they may sneeze the seeds of clouds.
Emiliania huxleyi phytoplankton
infected with a virus shed the small
calcium carbonate plates that make up
their shells much more quickly than do
healthy phytoplankton. Kicked up by
thrashing waves into sea spray, those
calcium bits may become part of the
complex dance of cloud formation,
researchers report online August 15 in
iScience. This is the first study to suggest
the role that viruses may play.
The finding adds to a growing body of
work showing that cloud formation is
regulated not just by physical processes,
such as evaporation, but also by biological
processes, says marine biologist Roberto
Danovaro of the Università Politecnica
Delle Marche in Ancona, Italy.
Phytoplankton contribute gases and
particles that can become “seeds” around
which water vapor in the air can condense
to form clouds. Studies in the Southern
Ocean have shown that phytoplankton
blooms increase the number of cloud-forming droplets in the atmosphere over
EARTH & ENVIRONMENT
Sick sea algae may help clouds grow
Virus-infected phytoplankton rapidly shed their tiny shells
A new algorithm analyzes the appearance of someone in one video (“input”) and transfers that
person’s facial expression, head pose and line of sight onto a person in another video (“output”).
That can generate footage of the second person doing and saying things she never actually did.
the ocean by about 60 percent each year.
In the lab, atmospheric chemist Miri
Trainic of the Weizmann Institute of
Science in Rehovot, Israel, and colleagues watched how the progression of
a phytoplankton viral infection altered
the shedding of calcium carbonate plates
as well as the composition of sea spray.
The team filled a 10-liter container
with several liters of seawater and added
a population of E. huxleyi. Then the team
added a phytoplankton virus.
Even healthy E. huxleyi shed some of
the tiny plates that make up their shells,
called coccoliths. But when infected by
the virus, the phytoplankton tend to
burst and rapidly drop their coccoliths.
Within three days, seawater surrounding
infected phytoplankton had three times
as many plates as did water around the
microbes’ healthy counterparts. To simulate sea spray, the researchers pumped
air through the tank and measured the
particles released by breaking waves and
bursting air bubbles.
Spray above virally infected populations had about two particles per cubic
centimeter of air — about an order of
fooled, on average, 50 percent of viewers.
But people may have been more critical
of doctored footage during the study
than they would be normally because
they were primed to anticipate fakes.
Even when participants were watching
genuine clips, 20 percent, on average,
still believed the clips were not real.
The software has some limits: It can
fiddle only with videos shot by a stationary camera, framed to show someone’s
head and shoulders in front of a static
background. And the algorithm can’t shift
a person’s pose too much. That is, a clip of
Putin speaking into the camera couldn’t
be edited to make him turn around,
because the software wouldn’t know what
the back of Putin’s head looks like.
Still, it’s easy to imagine how this
kind of digital puppetry could be used
to spread misinformation. “Learning
how to do these types of manipulations
is [also] a step towards understanding
how to detect them,” says computer sci-
entist Kyle Olszewski of the University
of Southern California in Los Angeles.
A future computer program could study
both true and fake videos to learn how to
spot the difference. s
magnitude more particles than in the
spray above uninfected phytoplankton.
Once in the atmosphere, the flat, aerodynamic plates tend to linger, increasing
their opportunities to affect cloud formation in various ways. One cloud-boosting
role the plates may play is through chemical reactions in the atmosphere, forming
calcium nitrate particles that can become
giant cloud condensation nuclei.
But the particles may also hinder cloud
formation, the study’s researchers say,
by removing other potential cloud seeds
from the air. Phytoplankton-emitted
dimethylsulfide gas, which transforms
into sulfuric acid in the atmosphere,
has also been hypothesized to help seed
clouds. But in the presence of particles
with relatively large surface areas, such
as the coccoliths, the acid may condense
onto these particles instead.
There are still many unknowns when
it comes to how large of a role coccoliths
actually play in cloud formation and
whether they may do more to help or
hinder cloud seeding, says atmospheric
chemist Patricia Quinn of the National
Oceanic and Atmospheric Administration’s Pacific Marine Environmental
Laboratory in Seattle. She notes that,
for example, no one has yet measured
the actual number of coccolith particles
in the atmosphere over the ocean. s