National Geographic: Rhythms of Life Page #2

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use the light to see.

They need it to grow their food

gardens of brown algae

that flourish within their

transparent bodies.

Denied sunshine,

they would starve.

As the sun arcs overhead,

shadows of the surrounding walls

darken the surface of the lagoon.

Just below, the jellyfish ferry their

microscopic passengers,

keeping them always in the light.

When the sun sinks,

so do the jellyfish,

dropping down to the ocean floor

where the algae can find their own

nourishment.

Even without sight, the jellyfish will

know when the sun returns again.

In the surface waters of the oceans

most creatures take their cue

to feed or rest

from the rhythm

of light and dark.

Now, members of the night

shift hurry to take the stage.

Roused by light-sensitive cells that

announce the return of darkness,

these prickly browsers

set out to graze.

Sea urchins find their prey

and their way around

by touch and by taste.

Each night clouds of plankton rise

from the deep to feed

drawing out the coral who fish

the waters with feathery nets.

A few, sharp-eyed fish operate by

sight in the dim light before dawn.

Like a cat in the dark, the lionfish

can pick out its prey.

The lionfish will slip into a crevice

to hide from the daytime;

eyes sensitive enough for half light

may be too delicate for bright sun.

Daybreak brings the morning

rush hour to the reef.

Far more complex than jellyfish

or sea urchins,

most fish depend on sight to survive.

Without the sun they are virtually

blind to navigate their world,

to find their food,

or signal to their kind.

A kaleidoscope of colors enhances

the play of daylight on the reef.

For the fish, stripe and hue holds

clues and communications,

helping them to identify mates,

predators, and prey

in the busy rainbow of the reef.

Trailing twilight in its wake,

a manta ray flies in,

to harvest plankton when again

they rise with evening.

Sunlight fades, taking with it

the world of color,

and the day shift streams off the

reef for the safety of deeper water.

And once again,

the great earth wheels round.

The line between light and darkness

divides those that live by land

as well as the creatures of the sea.

And even the land and sea themselves

breathe with the rhythms

of day and night.

Given off by day,

water vapor now rises, cools,

and condenses in the night air.

From earth, through plants,

into the air,

and back to the earth again

the endless cycles of replenishment

and renewal.

The plants of this Australian

rain forest

have been in tune with the rhythms

of the sun for eons.

Here, an acacia tree wakes up

and stretches for the dawn.

Like a sundial in the trees,

the play of light and shadow

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