Ocean Sunlight

0

by Holly bang
&Penny Chisholm

IVE INTO THE

Now flip over slowly, and look up.
The water is shimmering with ligt

my

I am your sun,
your golden start
All ocean life dependson me;
so does all life on land.

In your forests, prairies, and and pull in
your gardens, green plants carbon dioxide
catch my sunlight-energy. from the air.

They pump in water
from the ground

Plants use my energy All the while, the plants
to build these send oxygen into the air—
the oxygenyou breathe.
molecules into

This is

photosynthesis:

plants making life with
light—my light.

Animals—yes,animals like YOU!—eat the plants,
or you eat other animals that have eaten plants.

You are links in food chains—the chains of life.

And as you eat,you breakapart the sugar from the plants

and use its energy—MY energy!--to live.
You breathe out carbon dioxide,
andthe plants pull it back in.

Everything is connected.

All oceanlife is part

of food chains, too.
And every ocean food
chain starts when plants

catch my light.

But where
are the ocean's plants?

,인가`4넣

The seaweedsyou find
growing along the shore feed
some sea creatures living THERE.

But in the vast, open ocean,far
from land, do you see seaweedforests,
seaweed gardens, seaweedprairies?

Not

You see no green at all—none.

In the' open toceanyou»ee only

greenThen where are the ocean's

They're right before your eyds

They're everywhere—
in countless shapes and sizes.

But they'reso small you need
a microscopeto see them.

o

billion billion

Of these tiny plants—

Thewarecalled,

phytoplankton;

Phytoplankton form )tt€ergreat
invisible pastureof&the sea:

'you:breäthe€everytdav-
comes'from'green

•is)bubbling @€6CaiI.thejtfii9t
phitoplanktbmfloatiågimyoui{seås:

Phytoplankton can grow very fast.

If it has enoughlight and nutrients,one

phytoplankton can grow and becometwo

in just a day or so.It splits into identicaltwins!

So the billion billionibillion:
phytoplankton in the

ANOTHER billion billion billion

f themselves every few days!'And

just as fast as they make
more of themselves...

000 upt

Aniå1aIS=mostIy

tiny: onesicalled
0zooplankton—eatråbout
0 aibiIIiÖn billion)billion

phytoplankton every/day!{So
plytoplankton numbers stay(about
the same.As the iooplankton grow and
make more of THEMSELVES,bigger creatures
gobbleJHEM up about as

And so it goes.

My light-energy,

first caught by phytoplankton,

flowsithrough
the
from the tiniestlgreen plants

to the biggestfish orwhale'

But here'sa puzzle for you.
My light cannot reach deeper
than the ocean'sthin, top layer,so tha
wherethe phytoplanktonhave to liv

thaTerhedepadirtekceehpstbc,lomalcdokowdnaaltereksr-ss-,sdutaanrrdkleeesrrsnetnhaiagthnht.

Phytoplankton cannot live there.

But lots of animals do!
Where do these animals get their food?

Someuse their-glowing lights to ani als

an at t em.

Some

éat

each

other.

Some swim up

at night to feed
on phytoplankton.

Others wait. •

for SNOW.%

This ;npw isn,'t'mäåeøof ice, "Marine•séow" iny
nkton
flakes from'iiing ahimals and.phyto
guts, •
live and adie#freir pöop and mueusøecarcasses
ther
sink downand down,like falling flakes of_

Mirine snowj' hutritiousfood for bacteria,a

creatura living in$hesunleqs bélly of thél

Nothing goesto waste.

As bacteriaand animals eat the fallin now,
they breakit down and push

leftovernutrients and carbon dio
out into the black, deep sea wat

BUT WAIT!

Phytoplankton all live in the sunlit surfacewaters
MILES above'.They need those nutrients to make more

of themselves.And without more phytoplankton,
the ocean animals will die!

Howcan those deep dark waters—richwith nutrients—
rise all those miles back up into the lightGo the
phytoplankton can use them once again?

I, your sun,
pour my light
onto Earth each day.

My sunlight powerswinds that build
great storms and mix the water
layers of the seas.

My light helps drive enormous currents.
They thrust the deep sea waters, rich with

nutrients and carbon dioxide, up,

all the

way back

up

... to the sun-filled
topmostlayer where the
billion billion billion phytoplanktonpull those

nutrients and carbon dioxide in again—
and catch my light again.

Now they can keep mysunlight-energy flowing;
ever,flowing,

through new chains of life.

0

00 一O

, and

to your deep
and restlesse

seas.

NOTES "OUT THIS BoOK MyLight.) Plants are able to live by catching
some of this sunlight, which they.use in
The world's Oceans.cover photosynthesis,the process briefly aescribed
seventy percent of our planet,
and they teem with life. In ' early in this book. (For a moie detailed
fact, the combined weight of explanation of photosynthesis on land, see our
all the animals in the sea is
roughly equal to the weight• second book, Living Sunlight: How Plants Bring
of a billion elephants!With
so many creatures living in the oceans,how do the Earth etnoaLbilfees.)pFlaunetlsedPtobtyetehde sun, photo.
they find enough food to eat?They all depend synthesis almost all
on microscopic plants called phytoplanktonthat
float in the sunlit topmost layer of the'seas.Even living things, both on land and in the sea.It is
life in the deepest darkest depths of the oceans
depends on the growth of these sunlight-fueled the most important processon Earth. Without
plants. 'And—even more amazing—so do you! it, our planet would be a ball of rock and
This "invisible pasture" produceshalf of the
oxygen you breathe!In this book, OceanSunlight, water.—and
we introduce readers to the'wondrousprocesses
•taking place every moment in our seas,and we 'PHYTOPLANKTON FEED OCEAN LIFE:
describe how most of the presentforms of life
on Earth—including ourselves—could not exist Each gallon of sunlit surfac- sea'water.is home
without them.
to millions of phytoplanktc bThey belongto
These notes are just a beginning;to thoroughly
explain what we know about how our oceans thousandsof different sie(
. work would require including numerouscollege
textbooks from many fields. And with a subject so with varying shapes,sizes,
vast, there are 'exceptions to the generalizations
we have presented.We touch on some of these colors, an ornamentation.'
below and challenge you to keep exploring!
Like a bountiful meadow t!
feedsa multitude of

animals on land, these
microscopic phytoplankton
create an enormous underwa "invisible
pasture"that feedsall life in Ole sea—and
produceshalf the oxygen in our air! Although
mest people have n•everheard of phytoplankton,
•these tiny. plants are critically important to the
existenceof all life on Earth. Phytoilankton
are the unsung heroes of our planet.

LIFE DEPENDS HOW PHOTOSYNTHESIS woiK?

ON THE SUN. During phopsynfhesis, plants absorb sunlight
using chlorophyll,a green pigment in their leaves.
Our story beginswith the• In this extraordinary process, plants are able to
sun, the golden star that
use the sun's energy to make
lights our world. Every day, their own food—a *formof
a tiny portion•ofthe sun's
heat and light strikes the Earth—but that tiny sugar called glucose,wych
amount is,much, much more than all the energy is "energy central" in all the
frpm coal, oil, and gas we use each day.(To learn
more about the sun's energy,see our first book, functions of life.To make

glucose, plants draw in

bon dioxide (C02) from fopd—eneegy tha•tcame originally from
t air and suck up water plants—to live and grow.Using oxygen from
the•air around them; aninials "burn" the
O) from the ground. They • sugar—that is, they break apart the bondsof
u he sun's energy to split sugar molecules and breathe out carbon dioxide.
t ater into hydrogen (H) This process is called respiration.' •

oxygen(02) and link the The chemical reaction is:
on atoms (C) from carbon dioxide into chains
tfia#become sugar molecules—stored energy. SUGAR (c,H1206)+ OXYGEN GAS (02)
react and make ..
Héreis the chemical reaction:
CARBONDIOXIDE GAS (C02)
CARBONDIOXIDE GAS (C02) + WATER(1420) + WATER (H20) +.CHEMICAL ENERGY
+ SOLAR ENERGY (PHOTONS)
react and make ... The carbon dioxide released in respiration
becomes available for plants go use again in
SUGAR.(CéHn06) + 'OXYGEN GAS (02) photosynthesis. •

The illustrations this book showoxygen Each year on Earth, billions of tons of plant
atomsas white döv, carbon atoms as black dots, material are produced
through photosynthesis.
(H20) • (C02) Muchof this plant material
is consumedby animals
HOW DO PLANTS FEED and respired back into the
atmosphere as C02 while
ALL LIVING THINGS? oxygen is consumed.Carbon

Throughfood chains. When one living thing eats *änåoxygc., keep cycling between the plants and
another„it•becomesa link in a food chain. Plants animals, driven by the flow of the sun's energy.
are the first link in (almost!) every food chain
becausethey do not rely on other organismsfor WHAT FEEDS.THE FOOD CHAINS
.food.They make their own food, sugar, throdgh
OF THE SEA? 4
photosynthesis.Plapts turn
Photosynthesis,of course!The sun provides ocean
some of the sugai into
proteins, fats, and other Plants with the energythey needto grow and
molecules that become food
for the animals that eat reproduce,exactly as'it does for plants on land.
the plants. For example,
in this book you'll find an But the majority of the ocean'sphotosynthesis
illustrationwhere plants are eaten by mice,and
the mice are eaten by a snake, which is eaten is done by phytoplankton.
by a raccoon,which becomesfood for a cougar.
Eachanimal uses the chemical energy in its Some phytoplankton facts:,

•You need a micrÖscopeto see all but the

largest phytoplankton.

• Thé thousands of'different

species have a size range

far greater than we can

show in these illustrations.

Membersof the smallest'

s

species are 11100ththe width of a human hair. their photosynthesisto grow
If the smallest ihytoplankton were the size of and multiply. When they have
a pea, the largest would be the size of a hot enoughsunlight and all the

air balloon! • nutrients they need—such

• Phytoplankton are some- as the.nitrogen, phosphorus,
times called "algae." Many and iron that all living things
are distanily related to requirefor their metabolism—
the seaweedslining our
seashores. phytoplankton can double their numbers each

• Phytoplankton 'are day.At this rate, a single,phytoplankton cell
responsible for half the photosynthesison
Earth, even though their collective weight is , could grow into a billion cells in just one
only 0.1% of all plants and trees on land.
month! Sometimes phytoplankton "bloom" this
• Finally, while this book focuses on ocean way in shallow ponds, marshés, and coastai
phytoplankton, they have close.cousins who
live in in our ponds,marshes,streams,soils, waters that are rich with nutrients that have
and even in ice! Where there is water and flowedin from the land—largely from fertilizers
sunlight, you will usually find phytoplankton. and untreated sewage.When this happens, the
phytoplanktongrow faster than they can'
HOW PHOTOSYNTHESIS CHANGED
EARTH'S ATMOSPHERE' be eaten and form dense
patches that slowly sink to .
Three billion years ago, when primitive ocean the bottom: Bacteria feast
were the only life on Earth, there was on these pat-hes, and as
they do, the' •espire and
no oxygen in Earth's atmosphere!But some Ofe consume so •ch oxygen—
those primitive bacteria. more than th, phytoplank-
were the ancestors of the ton can produce—that Chefish ah-J other sea
phytoplankton we see today, life cannot live there anymore.Thi' .sjwhat
and they developedthe causesthe "dead zones" in some toastal waters;
ability to photosynthesizeA.s their ecosystems have become ÜnbaIanced
they spread and evolvedand becausethe influx of nutrients from the land
grew and photosynthesized has causedphytoplankton population explosions.

over more than a billion years, the oxygenthey -WHAT ABOUT OCEAN
released slowly leaked into the atmosphere.Had AREAS FAWFROM LAND?
this not happened,the plentiful oxygenwe all
breathe today would not exist! In-the vast open oceans,
awayfrom land,there is still
HOW CAN SUCH TINY ORGANISMS abundantsunlight and
PRODUCE SO MUCH? for photosynthesis,but CO2

Phytoplankton are streamlined"photosynthesis ypstnhoyluasrutotnremukiemtganoh,ytnasrh.neaIafdcrvyeytecohslpuiicsnlaebglrniucfmtreiyloid;tmtoshafetwchhyaioetaruhprgsieerneona,wttfvhoeaterrhisleaooaxbcfnaeledpmahonlpuynlmteloy,b- e,r,
machines."Since they have no stems or trunks or
roots to maintain,they use all of the productsof

b the size of your house and how fast you ball fields) there is no light—none—and, with
canbuild it will depend on your.supply of no light, there are no phytoplankton.If the
nails—whichare small but essential, Similarly,
phytoplänktongrowth and reproduction depends ocean weré a twenty-story
onthÉ supply of nutr!ents available.e there would

And since phytoplankton light and phytoplankton
are generally eaten as fast only on the top-story.The
as they reproduce,their surface waters are like a
population stays about the thin, green,living film that
same. It may be difficult.to feedsall life in the sea.
imagine how:s.omething that But naturehas lots of waysto distribute
is cÖnstanUychanging— its bounty! During the day, many animals spgnd
growingand dying—appears to stay the same. their time hovering below the sunlit surface
Imaginea bathtub half filled w!th water.Now layers and then swim up at night to eat
phytoplankton.This way,theiYe protected from
openthe drain turn on the faucet so the predators Gy darkness. Just before dawn, they
nowin equals the flow out. The amount of water swim back down to the safety o' the dark,
in the tub stays the same,but the water going deep waters.
downthe drain is replaced by new water. In Many other animals spend
a similar way, phytoplankton are constantly their entire lives in tie deep
sea. Some feed on each other,
reproducing,replacing often.luring their prey with
thosethat are being eaten appendages that glow with
or dying, so their numbers blue light. Others feed on
"marine snow.
stay about the same—just
as the amount of water in WHAT EXACTLY IS MARINE SNOW?
.thetub stays the same. It
is only Whenthe flow in and Marinesnow tiny bits of organic.matter—
.the flowout are not equal—when the matter made by living things—ethat have been
growthand death are not the sanie—that sloughed off of creatures as they are eaten or
the balance is disrupted. This concept eisvery as they die and fall apart. Each "snåwaake" is
important,and applies to all living things in a
food chain. colonizedby microbesthat
live off its nutrients, turning
How DOES THE FOOD CREATED it into .atiny oasis of life. As
BY PHYTOPLANKTON REACH LIFE IN each piece of snow settles
THE DEEP OCEAN? slowly down and down, the
microbesdigest it and grow.
Becauseboth water and
phytoplankton absorb Sun- They, too, become food for
light, the oceansget darker the deep 'ea animals.Very little reachesthe
and darker the deeper down •bottom of the sea.
you go. Below six hundred
feet (the length of two foot- Some'deep sea organisms have elaborate
devices for capturing marine snowflakes,

which are their sourceof and the two layers do not mix easily.When
food.What looks like a big marine snow,settles from the surface and
. creaturein this illustration, decomposesin the deep water, the nutrients
for example,is actuallyae
three- to si'-foot-wide net and carbon dioxide that have'been released
of mucus made by the tiny,' tend to•staythere. But not forever.
inch-long larvacean that's inside!The larvacean
uses the net to catch the falling "snow." TWOHAKTEEGPOTEYSEDOOWCENANMAULSITV.tEC,OME UP.

MARINE SNOW THE ONLY*OOD Deepwaters,and the nutrients and carbon 9.
THE' BOTTOM DWELLERS EAT?
dioxide they carry, have several ways to return
No. Every once in a while a dead whale (or
other large animal) sinks to the bottoåt—a to the surfåce.First, when surface•waterscool
"whale fall." Whole ecosys-
tems immediately assemble in winter, winds are strong enough to mix the"
to feasi. It takes decadesfor
the whale to be compleiely ewaterdownwardand force some deep water•ui.
consumed, bones and all. The
little feathery red worms on Second,along the western coasts of continencs,

•the bones in the illustration winds blow surface waters offshore,and deep
are Osedax ("bone devourers"),the last guests
at the >anquet. Ultimately, everything is eaten. water rises to replace them. Finally, the oceans
Remember,each bit of organic matter that
settles to the deep sea can be tnced back to are connected through global
sugar formed by the photosynthesisof phyto-
plankton in the surfacewaters.As this matter is tion—a sort of "conveyer belt' •propelledby
consumed by animals and bacteria of the deep,
it is converted back into C02,which, along with a variety of forces,including energy.
Over vast regions,the belt 1
• nutrients, is excreted into the deep sea water
and trapped in the deepocean. sends very deep water up to •

TRAPPED? WHY? the surface layer, replenishinii

The physics of the oceans are complex(the the supply of nutrients thai
subject of another book!) and intimately con:
nected with all that lives there.The top few the phytoplanktonneed to

hundred feet of ocean waters keep thriving.
are diluted by•rainand kept
relatively warm by the sun. If you Wereable to ride

These surface waters remain on.this conveyerbelt, it would take iou about
, fifteen hundred'yearsto complete the journey
above the colder, saltier, and
thus heavier,waters below, through all the oceans, moving between the
surface and deep waters. All the oceans-of our
planet are connected in this way.

ADDITIONAL•INFORMATION

There are so many important, related concepts
that we could not possibly cover them all in

this book.
For simplicity,we say,"all life in the oceans

depends on phytoplankton photosynthesis."
This is not .completely true. "Chemosynthetic".
bacteria,for example,can use the energy
containedin chemicalcompoundsto turn

dioxideinto sugar without the sun. We these issue'sin OceanSunlight becauseour in-
do yet know how abundant they are in the tent was to describe how ocean lifeworks, not
sea. do know they form the base of the food to iounå alarms. Through'understanding ocean
chain roundthe deep sea volcanoes—the'
hydrothermavlents that existin various.placés • ecosystems, we can make

better decisionsabout how

onathe ocean floor. The bright red•tubeworms in to live on this remarkable
planet that keeps us alive. We
one.of the illustrations are hope this book encourages

filled with chemosynthetic

bacteria. These are symbiotic you to learn more!

the

worms as their home and To my GreenSustenance
feed them in return. and to Monika,my Other Sustenance— M.D.

In our discussion, we have

alsoshortchanged.,Emssiveamounts of bacteria To all my students, Prochlorococcus,'andDon,
who have taught me much— P.C.•
thatfloat everyyhe. Orin the sea and are central
With MANYthanks, especially to Jim Green!And
to "oceanmetabolism."tThese are not the kinds to Bruce Robison,Larry Madin,.SteveRintod, John
Cullen, Tom Malone,Trish and Dave Mauro,
of bacteria that cause human disease, which are Kashtan,JessieThompson,Katya Frois-Hoü, md
dnlya•tiny,tiny fraction of Earth's bacteria.On to the whole Lasche family. And to Kathy Westrayö
thecontrary,these are among the huge majority Grace Kendall, and Caröl & BonnieVerbwg, Ed
finally to ElaineMarkson,who got it throu*!
ofbacteriathat maintain our planet.
A millionof these ocean bacteria live in every THE BLUE SKY PRESS

teaspoonof sea water. Many of them groy by
usingthe carbon compounds made by phyto-
planktonduring photosynthesis. Others, as we
dodiscussin the book, grow on particles like

marinesnow. In Atheprocess, they Text copyright @ 2012 by Mo!lyBang and Penny
Illustrations copyrigit @ 2012 by Molly Bang
releasenitrogen, phosphorus,
• iron, and other nutrients—- All rights reserved.
No•partof this publication may be reproduced,stored
recyclingthem for use by a retrievalsystem,or transmittedin any 6rm or by my
otherliving things. These means, electronic, mechanical, photocopying, recording. or
bacteriaare also vital to otherwise,without wri!ten permission of the publisher.
the ocean's food chains.
For information regarding permission, please write to:
Permissions Department, Scholastic Inc.,

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UNDERSTANDINGOUR OCEANS?
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Becauseour lives depend on them. As land- Library of Congresscatalog card number: 2011024823

dwellersw, e tend to think of oceansas alien ISBN 978-0-545-27322-0 19 2021 2223 24
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Printedin China 38
worlds—vastand limitless—relatively immune to
' This book was printed on paper containing 50%
Ourinfluence.Yet in the past few hundredyears,
wehave begun to change the chemistry of ocean post-consumerwaste recycled materials.

First printing, May2012

Watersand life in the sea. We did not discuss Designed by Kathleen Westray