National Geographic: Ocean Drifters Page #3

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It's a 500 mile swim to shore.

Richard Harbison

and his colleague Larry Madin

are among the few researchers studying

how these ocean drifters behave

in their own environment.

The air tanks limit them

to 25 minutes per dive.

So they get just a glimpse of how

these high sea drifters really live.

Harbison and Madin specialize

in creatures of incredible delicacy

known as jelly plankton.

This underwater world changes

by the hour.

Many species stay away

from the brightly lit surface by day,

so these researchers dive round

the clock.

Under the cover of darkness,

a whole new world of creatures rises

from the depths.

It is the largest animal migration

on the planet,

and it happens every night

in the oceans.

This sea snail

joins a glorious host of species

as they ascend to feed at the surface.

Life as a jelly

is an ingenious adaptation.

There are no hard surfaces

to run into on the open sea,

so these drifters don't need

a sturdy body.

The gelatinous form gives them the

same buoyancy as the water around them

They've evolved for life at sea by

becoming organized seawater themselves

Near the surface, the smaller drifters

feed on minute plant life

that's been growing all day in the sun.

Bigger animals come up to feed on them

The great oceanic food chain

begins here

and everything else depends on it

This weird apparition is a killing

machine for small crustaceans.

The writhing arms of this comb jelly

startle its victims,

which flee straight into the wing

like feeding lobes

at either end

and become entangled.

It's easy to become mesmerized

by the delicate structures

of some ghostly creature turning

gently in the currents.

You can see the beating of the heart

through the transparent shell.

Its mouth parts

are like an easterlily.

Ocean conditions have reshaped

it beyond all our notions

of what a snail should be.

Look in another direction,

and there's a salp chain grazing

on small plant particles.

This jelly can reproduce

with extraordinary speed

to take immediate advantage

of a new food source.

The salp sprouts new individuals

like a chain of paper dolls.

The gelatinous form makes

for efficient feeding.

It allows this siphonophore

to spin out lengthy tentacles

like fishing lines.

It twitches its crustacean-like lures

to entice its prey.

In the boundless world of mid-ocean,

with the sea bottom miles below

and no other surfaces nearby,

a jelly is the only niche

for other species.

One animal's body can become

the whole world for another.

A crustacean deposits her offspring

on a comb jelly.

As they grow, they devour their host.

Crustacenas eat jellies,

and jellies eat crustaceans.

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