CoralReefs

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Written by Paula Schricker

Coral ReefsA Reading A–Z Level N Leveled Reader

Word Count: 918

LLEEVVEELLEEDD RREEAADDEERR •• NN

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CoralReefs

Coral ReefsLevel N Leveled Reader© 2003 Learning Page, Inc.Written and Illustrated by Paula Schricker

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Coral Reefs

www.readinga-z.com

Written by Paula Schricker

Photo Credits:Front cover: PhotoDisc; back cover, pages 4, 5, 7: Florida KeysNational Marine Sanctuary; title page, pages 6, 9, 10: Mohammed Al Momany/NOAA; pages 8, 12, 17: Florida Marine ResearchInstitute; pages 15, 16: USGS/Coastal & Marine Geology Program;pages 18, 19: Paige Gill/Florida Keys National Marine Sanctuary;page 20: www.ecoreefs.com.

CorrelationLEVEL N

Fountas & Pinnell MReading Recovery 20

DRA 28

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Table of Contents

Introduction . . . . . . . . . . . . . . . . . . 4

What Is Coral? . . . . . . . . . . . . . . . . 6

A Busy UnderwaterCommunity. . . . . . . . . . . . . . . . . . . 9

Where Do Corals Live? . . . . . . . . 11

Threats to Coral Reefs . . . . . . . . . 15

Protecting the Reefs . . . . . . . . . . . 18

Glossary. . . . . . . . . . . . . . . . . . . . . 21

Introduction

Coral reefs are massive underseacommunities. Almost one-quarterof all the plants and animals in the ocean live around coral reefs.The world’s reefs are home to over4,000 kinds of fish and 700 kinds of coral. The reef is like a hugeunderwater city. The “buildings”are made of corals, and thousandsof animal inhabitants bustle about,day and night.

Many kinds of coral, fish, and sea creatures live in a reef.

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There are hundreds of kinds ofcorals. Most of them are dividedinto hard, or “stony,” corals, andsoft corals. Stony coral polyps formhard skeletons. When the polypsdie, they leave their skeletonsbehind. Millions of these hardskeletons form a reef. Most kinds of stony corals live together withplant-like living things called algae.The algae make food for the coral.

What Is Coral?

Corals may look like rocks orplants. But they are actually madeof tiny animals called polyps(PAHL-ips). Most polyps arebetween the size of a pinhead andthe size of a pea. One branch ormound of coral can have thousandsof these tiny animals. Each polyp has a sac-like body and a mouthsurrounded by tiny tentacles. Atnight, polyps extend their tentaclesto catch tiny animals to eat.

Polyps open their tentacles only at night.

These feathery polyps form branches.

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Corals are often named after whatthey look like. Stony corals includebrain corals, which look like brains,and elkhorn corals, which look likeelk horns. Soft corals often look likeplants or trees. Sea whips and seapens are long and narrow. Sea fansare wide and branching.

Soft corals grow wood-like coresinstead of stony skeletons. They areable to bend with the tides. Somekinds of soft coral are poisonous,and will sting if touched.

(Left) A sea fan (a soft coral); (right) a brain coral (a stony coral) Elkhorn coral branches out like an elk’s horns.

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Crustaceans like shrimp, lobsters,and crabs also prefer reefs. Seaurchins and starfish catch clams andshellfish hidden among the coralbranches. Sea anemones hide inshallow crevices. Large holes makegood homes for moray eels. Nospace is wasted in a bustling reef.

A Busy Underwater Community

Most people think of brightlycolored fish when they think aboutreefs, and with good reason.Thousands of fish, from largesharks to tiny gobies, inhabit reefs.Some live off the algae and coral,while others eat other fish.

Schools of brightly colored fish are common on reefs.Reefs offer many good hiding places.

Also, corals are very sensitive toexcess salt and debris in the water.They do not grow well near themouths of rivers, where dirt andrunoff flow into the sea.

Corals are very slow-growing.Some living coral reefs begangrowing almost 50 million yearsago. Most reefs are between 5,000and 10,000 years old. Stony corals,like brain corals, grow slowest.They add only 5 to 25 millimeters (0.2–1 in.) of skeleton per year.

Where Do Corals Live?

Most reefs are found in warmtropical waters, close to shore. Theycan also grow where warm currentsflow from the tropics, such as inFlorida and southern Japan. Coralgrows best in warm water, between21 and 29 degrees Celsius (70–85° F).Since algae need sunlight to makefood for the coral, corals must livenear the surface.

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Where Corals LiveThe dark areas of the map show the location of coral reefs.

Large brain corals can be thousands of years old.

An atoll forms when a reefsurrounds an island, and thatisland sinks beneath the surface.The reef forms a circle with alagoon in the middle. The largestatoll, in the western Pacific, has alagoon over 97 kilometers (60 mi.)across.

There are three types of coral reefs:fringing reefs, barrier reefs, andatolls. Fringing reefs sit close to theshore. They are common in Hawaiiand parts of the Caribbean.

Barrier reefs have a larger lagoon,or area of water between the reefand the shore. The largest reef inthe world is the Great Barrier Reefin Australia.

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Cross section(above) andview fromabove (right)of an atoll

Cross section of abarrier reef

Crosssection ofa fringingreef

Another condition known asbleaching occurs when somethingcauses the coral’s algae to die.Without the algae, the coral turnswhite as its skeleton showsthrough. Sometimes, coral canrecover from bleaching. But if thesituation that caused the bleachingdoes not change, the coral will die.Some reefs are threatened by toomuch sand and mud in the water,which can suffocate the coral.

Threats to Coral Reefs

Coral reefs are very fragile, andmany things can damage them. The two things that cause the mostdamage are disease and humans.Some algae diseases, like whiteband and black band diseases, arecaused by bacteria that growbecause there are too manynutrients in the water. Thesediseases can wipe out an ancientcoral reef in weeks.

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A dark ring resulting from black band diseaseThe white area of this coral has been bleached.

Protecting the Reefs

Coral reefs are an importantresource. Reefs help shelter coastsfrom storms and floods. Much ofthe world’s seafood comes fromreefs. Reef plants and animalsprovide many important medicines.

Humans are responsible for most of the destruction of coral reefs.Fishing methods that use poisonsand explosives have destroyed over half the reefs in thePhilippines. Seaside resorts andhomes create erosion and runoff,choking reefs. People damage reefsmore directly, too. Boats break offlarge chunks. Divers drop theiranchors directly onto reefs or standon the fragile coral.

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Boats break off large chunks of coral.

This officer’s job is to watch and protect coral reefs.

Almost a quarter of the world’sreefs have already been destroyed.Nearly 60 percent are threatened. It is up to all of us to help preventreef destruction. Even if you don’tlive near the ocean, you can help by conserving water and energy,and recycling. If everyone does hisor her part, coral reefs will remain a beautiful natural wonder thateveryone can enjoy.

Many countries have taken steps to preserve reefs. In Florida and onthe Great Barrier Reef, it is illegal to take fish, plants, or coral fromprotected areas. Humans and boatsare not allowed near many fragilereefs. But this is only a start.

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Divers still enjoy visiting fragile reefs.

These human-made objects are put in the ocean to provide a safe place for new coral to attach and grow.

erosion wearing or washingaway of the soil (p. 17)

fringing reef a reef very close to a shoreline (p. 13)

lagoon shallow, calm waterbetween a reef and theshoreline or in the center of an atoll(p. 13)

polyps tiny individual coralanimals (p. 5)

runoff soil, debris, andpollution that flowsfrom streams and riversinto the sea (p. 12)

Glossary

atoll a circular reef formedwhen coral growsaround an island, and that island sinksbeneath the surface of the sea (p. 13)

barrier reef a reef that sits fartherfrom the shoreline; it forms a barrierbetween the open oceanand the calm lagoon (p. 13)

bleaching when coral turns whiteafter its algae die (p. 16)

crevices cracks and holes (p. 10)

crustaceans hard-shelled, many-legged sea creaturessuch as lobsters, shrimp,and crabs (p. 10)

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