- Phytoplankton may be small, but that doesn't mean they
can't do big things -- like change the weather to suit their needs.
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- A recent study funded by NASA's Earth Science Department
shows that the tiny sea plants release high quantities of cloud-forming
compounds on days when the sun's harmful ultraviolet rays are especially
strong. The compounds evaporate into the air through a series of chemical
processes that result in especially reflective clouds. This, in turn, blocks
the radiation from bothering the phytoplankton.
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- The findings not only confirm earlier theories that plankton
are linked to the creation of clouds above the ocean but could also lead
to a better understanding of how living things affect the Earth's climate.
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- "The take-home message is that all the processes
that are going on in the ocean and the climate are very tightly connected,"
said David Siegel, co-author of the study and director of the Institute
for Computational Earth System Science in Santa Barbara, California. "This
is really the impetus for other researchers to look into the whole cycle
of how biology and climate interact."
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- Siegel and Woods Hole Oceanographic Institution researcher
Dierdre Toole announced the results of their study in the May issue of
the Geophysical Research Letters, a scientific journal.
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- The two researchers performed the study on measurements
taken off the coast of Bermuda. There, they found that the ocean levels
of a compound called dimethylsulfoniopropionate, or DMSP, were directly
related to the level of ultraviolet radiation reaching the phytoplankton
that live near the ocean's surface.
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- DMSP is an important link in the plankton-to-cloud cycle
because, as it leaves the phytoplankton cells and enters into the water,
bacteria break it down into a chemical called dimethylsulfide, or DMS.
Evaporated water, in turn, carries the DMS into the air where the chemical
reacts with oxygen to form various sulfur compounds. These compounds collect
as dust particles that promote water condensation, which, finally, leads
to cloud formation.
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- The entire process takes place very rapidly, ensuring
that the plankton aren't under the sun's rays too long. In their study,
Siegel and Toole found that the upper layer of DMS in the atmosphere could
be replaced in just a few days.
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- That the process happens at all may be a sign that the
Earth is better prepared to handle climate forces like the depletion of
the ozone layer, which also blocks ultraviolet light, than previously thought.
However, Siegel believes it's too early to make such assessments because
it's unclear just how widespread the phenomenon is. It's also unclear just
how much ultraviolet light and other forces the system can tolerate.
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- The researchers now plan to create computer models that
explore how the presence and absence of phytoplankton might change the
climate. They also hope to add to their study by using information from
NASA's Sea-viewing Wide Field-of-view Sensor mission, which collects data
on shifts in visible light reaching the ocean's surface.
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- It's possible that the extended work will show that phytoplankton
do affect climate on a global scale, said Siegel.
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- If that's the case, it's also possible that scientists
who like to talk about the "butterfly effect" -- the theory that
the flapping of a butterfly's wings in one part of the world could eventually
lead to violent weather patterns in another -- may soon find that it's
more hip to talk about the "phytoplankton effect."
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