The Silent World
Why silent plankton: I took the words Silent Plankton from the title track of Akira Sakata’s beautiful jazz CD . jazz musician and composer of international standing , he is a trained fisheries biologist; the name of his regular group Harpacticoida will raise a smile with some. Akira was born in Kure city, Hiroshima on February 21th 1945 – he would have been just 6 months old on the 6th of August of that year when the atomic bomb was exploded over Hiroshima. Although Kure is some 20 or so km from the centre of Hiroshima, it surely is a very sobering thought. He studied marine biology at Hiroshima University and specialised as a fisheries biologist; plankton, as the food of fish, will have featured very prominently in his training and science. The words silent plankton are particularly perceptive as it gives us an important insight into the very special world of these wonderful creatures, far away from our own experience and we’re now going to go down and find out what it is like there.
Down there with the bugs: the smaller forms on
the ocean plankton live on a scale (1/100th to
1/000th of a millimetre) that most of us lack
an intuitive feel for. Perhaps not a spooky as the quantum
world but well along the way.
When you look at particle movements on the
microscopic scale they behave as if the water was viscous,
movements are slow and soon damped out.
It is often said that it would be like swimming in
molasses or honey.
This is a rather misleading way of looking at it,
as the viscosity of water is the same on our scale as on
theirs – it’s primarily about momentum rather than
viscosity. A
better way to understand it is to try to throw a balloon
across the room - try it and it will drive you nuts.
No matter how hard you try it will stop in a meter
or so. The
moving balloon have very little momentum and this runs out
almost as soon as
it leaves your hand.
Fill the balloon up with water and it’s a totally
different story – it will fly across the room to
devastating effect when it hits the wall on the other side
– not recommended as an experiment!
Supersonic
bacteria
: Here’s an example how things are down on
their scale:
bacteria swim at a greater relative speed than a jumbo jet
– about 30 or so body lengths/sec, sadly the poor old
jumbo can only bimble along at about 3-4 fuselage
lengths/second.
To achieve this pathetic performance it consumes
about 0.5 watts/gm, where as our bacterium rips along at
ten times the relative speed, consuming just a mere 0.0005
watts/gm in water, a much more viscous medium, with a
propulsion system, a simple flagellum, that was designed a
billion or more years ago.
We’ve got a long way to go to catch up nature, if
we ever will .
When a bacterium stops swimming is
coasts for just 0.1 Angstrom and stops within less than
one microsecond. The
distance between atoms in a molecule is ~1 Angstrom
(1/10,000,000th of a millimetre), so a
bacterium coasts for a small fraction of the length of a
hydrogen to hydrogen bond – it would be like stopping a
Formula One car in 1/10th of a millimetre –
driving full belt into a concrete block – to say the least
a very nasty experience, but it doesn’t seem to bother the
bacterium.
