Geology Reference
In-Depth Information
has known only a watery ocean existence, to be so suddenly wrenched up into a cloud
that could carry it for hundreds of kilometres before washing it out in rain into a new
region of the ocean where, with luck, there is an abundance of nutrients.
The most prolific DMS-producing algae are by far the smallest, perhaps because their
diminutive size increases their chances of making it into a cloud. These tiniest algae also
make foams and slimes that make it even easier to get airborne, and many of them have
a red pigment that protects them from the abundant ultraviolet light of the high altitudes.
One of the surprising properties of DMSP is that it is an anti-freeze, which works to the
alga's advantage, for as the cloud rises, it reaches regions of low temperature where its
water freezes out, only to fall earthwards as rain or snow. Thus DMSP may help the al-
gae to survive not only the saltiness of the ocean, but also the freezing temperatures in
clouds that the algae themselves have seeded.
Riding the Clouds
Find a comfortable place outdoors to watch clouds. Relax, and then look carefully
at their shapes and textures. Watch their movements in the sky, and then imagine
myriads of microbes riding in the clouds, triggering rain that washes them out into
pastures new. Imagine what it would be like to be a microbe swept into the cloud
by an updraft of air.
Now shrink yourself down smaller and smaller until you become a coccolitho-
phore surrounded by billions of other coccolithophores in a vast bloom floating
on the surface of the North Atlantic just off the coast of England. Feel the coolness
of the sea water as it caresses your chalky shell. Notice the tangy taste of the sea,
and how it gently rocks you from side to side.
It is the end of spring, and the increasing warmth of the sun has created a layer
of warm water on the surface of the sea that prevents currents from bringing you
nutrients from the depths below. You feel an aching hunger as the nutrients gradu-
ally run out.
The whole bloom, with you included, begins to sweat billions of cloud-seeding di-
methyl sulphide molecules into the air above you. Winds stir the surface of the
waters as the dimethyl sulphide molecules trigger the formation of dense clouds
above you.
