When the temperature soars, coral reefs might cool off by creating
their own clouds.
Research from the Great Barrier Reef off the Australian coast shows
that corals are packed full of the chemical dimethyl sulphide, or
DMS. When released into the atmosphere, DMS helps clouds to form,
which could have a large impact on the local climate.
In the air, DMS is transformed into an aerosol of tiny particles on
which water vapour can condense to form clouds. This sulphur compound
is also produced in large amounts by marine algae and gives the ocean
its distinctive smell. Algae play a vital part in regulating Earth's
climate, but no one had looked at whether coral reefs might have a
Graham Jones of the Southern Cross University in Lismore, Australia,
and colleagues measured DMS concentrations in corals in the Great
Barrier Reef and its surrounding water. They found that the mucus
exuded by the coral contained the highest concentrations of DMS so
far recorded from any organism. A layer rich in DMS formed at the sea
surface above the reef, where it was picked up by the wind.
"Although globally the emission of DMS from the Great Barrier Reef is
not huge, on a regional basis it is very significant," says Jones.
The big question now is what effect this will have on the
climate. "The coral is a concentrated source of DMS, which could
affect the formation of clouds in that region," says Peter Liss, an
environmental chemist and DMS expert at the University of East
Anglia, Norwich, UK.
The Australian team plans to study the impact of the reef and other
corals on local climate over the next few years. "We don't know how
the DMS emitted by the coral relates to cloudiness and the radiative
climate over the reef," says Jones. "That's the missing link."
But their findings help to solve a 30-year puzzle. Surveys in the
1970s found very high concentrations of aerosol particles in the air
above the Great Barrier Reef. The coral was thought to be the source,
but the mechanism by which the reef might have caused the aerosol
count to soar was not known. "They didn't know about DMS in the
1970s," says Jones.
The research also raises another intriguing possibility: that coral
can use a Gaia-like feedback mechanism to regulate the amount of
sunlight they are exposed to. The "Gaia theory" is that life on Earth
regulates its environment to keep itself healthy.
In lab experiments, Jones and his team showed that corals produce
more DMS when the symbiotic algae inside their tissues become
stressed by high temperatures or UV radiation. If this DMS seeds more
clouds, the coral could have evolved a way to reduce the water
temperature or UV exposure. "We've got a long way to go to
conclusively demonstrate this, but we've got a lot of ammunition,"
For 20 years, scientists have been hunting for evidence that free-
floating marine algae can operate a DMS-dependent feedback mechanism
to dampen global warming's effects. Because reefs are a static source
of DMS, it might be easier to show an effect, says Jones. "Coral
reefs would be a great place to show Gaia in action," he says. "This
is the first time that processes going on in coral reefs are being
connected to climatic processes."
Journal reference: Marine and Freshwater Research (vol 55, p 849, and
the upcoming issue)
There is a methanogen which breaks down dimethyl sulfide into methane
for hydrates and the dimethyl sulfide is a close intermediate to one
of the chemicals used in the China paper. So you have w/ the
hydrates a biogenic source toward CO2 for outgassing events and
therefore local/regional modulations and then you have a cloud
nucleation chemical but also you have per the China paper a cloud
nucleation chemical that is going to be sensitive to the DC fields.
Further a coral field, like the huge one just found in 200 feet of
water off the Florida coast, you will have concentrations of CO2 and
other biogenic materials (fish are attracted to them and so forth)
associated with their ecologies a bio source of chemical containment
that would go beyond diffusion from a relative conductivity
standpoint. Associated rain feedbacks then bring from the
terresphere nutrients. It's all a living deal.