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Make an Edible 

Coral Reef

You have probably seen pictures of coral reefs before—lots of colors, fi shes, and weird looking shapes! Coral reefs are not only beautiful to look 

at; they are also home to thousands of other species. In fact, scientists 

estimate that there may be another one to eight million undiscovered 

species living in and around reefs! Coral reefs support more species per 

square foot than any other marine environment. This abundance of living 

organisms is key to fi nding new medicines for the 21st century. Many 

drugs are now being developed from coral reef animals and plants as 

possible cures for cancer, arthritis, human bacterial infections, viruses, 

and other diseases.

Coral reefs are important for other reasons as well. Coral reefs are a 

breeding ground for many fi sh and other species, and millions of people 

and thousands of communities all over the world depend on coral reefs 

for food. In the United States, coral reef ecosystems support hundreds 

of commercial and recreational fi sheries worth more than 200 million 

What You Will Do

Make an edible model of a coral reef!

dollars. Local economies receive billions of dollars from visitors to reefs 

through diving tours, recreational fi shing trips, hotels, restaurants, and 

other businesses based near reef ecosystems. Coral reefs protect shorelines against waves, storms and fl oods, and help prevent loss of life, 

property damage and erosion. 

Despite their importance, many of Earth’s coral reefs are in trouble. Severe storms, water pollution, overfi shing, disease, global climate change, 

and ships running aground are some of the things that have destroyed or 

badly damaged many reefs. Because of these threats, coral reefs and all 

of the creatures that call them home may be in danger of disappearing if 

something isn’t done to protect them. NOAA is one of many organizations 

Spanish hogfi sh at reef.

Courtesy Florida Keys National Marine Sanctuary

You have probably seen pictures of coral reefs before—lots of colors, fi sh- dollars. Local economies receive billions of dollars from visitors to reefs 

Make an Edible 

Coral Reef
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participating in the U.S. Coral Reef Task Force, 

which was established in 1998 to protect and 

conserve coral reefs. Satellites are being used 

to map shallow U.S. coral reefs, as well as to 

watch for high sea surface temperatures that 

can damage corals and to detect harmful algae 

that can smother reefs. NOAA’s National Undersea Research Program does research projects 

to learn more about coral reefs, and restores 

damaged reefs in marine reserves and among 

deep sea coral banks.

Coral reefs need your help, too! More people 

need to understand why coral reefs are important and what needs to be done to protect them. 

Here’s a tasty way to start a conversation about 

coral reefs.

What You Will Need:

r One half sheet cake; if you want to bake your 

own cake you will need a box of cake mix and 

other ingredients listed on the box 

r Icing in various colors

r Food coloring

r Marshmallows, licorice whips, small cookies, 

candy sprinkles, or other edible materials 

for modeling coral reef animals and habitat 

features

Warnings:

1. Get an adult to help with baking.

2. Don’t eat too much!

3. Wash your hands before handling food! If more 

than one person is involved with this activity, 

you may also want to wear disposable gloves.

How to Do It:

1. If you aren’t familiar with coral reefs, read the 

sidebar “What is a Coral Reef?” You may also 

want to look at books about coral reefs or 

check out the Web sites listed under “Want to 

Do More?” 

A healthy coral reef ecosystem contains 

thousands of species, so you can’t really 

include everything in your model. Instead, 

plan a model that is colorful and interesting, 

using the images on these pages for ideas. 

Remember, the main idea is to create a model 

that will help start a conversation about 

coral reefs (and is also good to eat!).

Before you actually make your model, make 

a list of what plants or animals you want to 

include, and what materials will be used to 

show them on the model. Mounds of icing can 

be used for boulder-shaped corals. When icing 

mounds have hardened they can be sculpted 

to form caves and overhangs. Small cookies 

could represent plate-shaped corals. Coconut 

colored with green food coloring could be 

used for seagrass. Sponges could be modeled 

with small pieces of sponge cake (of course). 

Licorice whips could represent branching 

corals. Gummy fish or fish crackers on toothpicks can represent fish. Raisins or chocolate 

chips might be sea urchins. Of course, there 

are many more possibilities, and you probably 

already have a pretty good idea of things you 

could use in your model. 

2. If you plan to bake you own cake, mix the batter 

according to instructions on the box, and bake 

the cake in an oversized flat pan like a broiler 

pan or turkey roasting pan. Your cake will probably take less time to bake than the time stated 

on the cake mix box, because your cake will be 

thinner than usual.

3. The flat cake is the base of your model reef. 

Add the features you planned in step 1 to 

complete the model. This is a lot of fun to do 

with two or three other people, but be sure 

you wash your hands and wear disposable 

gloves so you can safely eat the model later.

A purple soft coral. Courtesy Florida 

Keys National Marine Sanctuary
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4. Show your model to your friends, parents, 

school, or other groups, and talk about why 

coral reefs are important, why they are in 

trouble, and what we can do to help save 

them. If you are using your model at school, 

your teacher may be able to arrange for you 

to make a presentation about coral reefs 

to another group of students, perhaps a 

younger class. When you have fi nished your 

presentation, you can say, “Now it is time 

for us to have a direct interaction with this 

model reef.” Which means everyone can eat 

the cake!

Want to Do More?

www.coris.noaa.gov/– Information about coral 

reefs from NOAA’s Coral Reef Information 

System

oceanservice.noaa.gov/facts/thingsyoucando.

html – Things You Can Do to Protect Coral 

Reefs, a National Ocean Service fact sheet 

www.coralreef.noaa.gov/– NOAA’s Coral Reef 

Conservation Program

coralreefwatch.noaa.gov/satellite/education/ – 

Coral Reef Conservation Program, Education 

and Outreach

oceanservice.noaa.gov/education/tutorial_corals/welcome.html – Coral Tutorial from 

NOAA’s National Ocean Service

www.teachoceanscience.net/teaching_resources/education_modules/coral_reefs_and_climate_change/how_can_you_help_coral_

reefs/ - Teacher resources from Teach Ocean 

Science

Grey snappers at the reef. 

Courtesy Florida Keys National Marine Sanctuary

Barrel sponges.

Courtesy Florida Keys National Marine Sanctuary Butter hamlet fi sh with soft corals.

Courtesy Florida Keys National Marine Sanctuary

Elkhorn coral and a white spotted fi lefi sh.

Courtesy Florida Keys National Marine Sanctuary
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Corals are animals that do not have backbones, 

and are related to jellyfish. The large boulders 

that we see in pictures of coral reefs are colonies 

of many individual coral animals called polyps 

(“PAH-lips”). Polyps are made of an outer cell 

layer called epidermis (“ep-ih-DERM-iss”) and 

an inner cell layer called gastrodermis (“gas-troDERM-iss”), with a jelly-like substance called 

mesoglea (“mez-oh-GLEE-uh”) in between. Each 

polyp makes its own cup-shaped skeleton called 

a calyx (“KAY-lix)” from limestone (calcium 

carbonate). The base of the calyx is called the 

basal plate, and the outer walls of the calyx are 

called the theca (“THEE-kuh”). Vertical partitions 

called septa extend part-way into the cup from 

the inner surface of the theca. The outer surface 

of the theca is covered by the soft tissues of the 

coral. Polyps have a mouth surrounded by a ring 

of arms called tentacles. The tentacles have 

stinging cells called nematocysts (“nee-MAToh-sists”) that polyps use to capture food. Most 

corals are carnivorous, and feed on small floating 

animals or even fish. Many corals also feed by 

collecting very small bits of floating material 

on strings of mucous, which they pull into their 

mouths. Food is digested by digestive filaments 

in the stomach. Waste is expelled through the 

mouth. 

Most reef-building corals have very small polyps, 

about one to three millimeters in diameter; but 

all of the polyps in a whole colony can make a 

limestone rock that weighs several tons! Individual polyps in a coral colony are connected by 

a thin band of living tissue called a coenosarc 

(“SEE-no-sark”).

As the polyps grow and multiply, the coral colony 

may become shaped like boulders, branches or 

flattened plates. Some corals form tall columns, 

others resemble mushrooms, and some simply 

grow as a thin layer on top of rocks or the skeletons of dead corals.

When corals reproduce, they release free-swimming larvae that can be carried many miles away 

by ocean currents. A new reef begins when these 

larvae attach to underwater rocks or other hard 

surfaces along the edges of islands or continents. 

As the corals grow and expand, other animals 

and plants join the reef system. Sponges and soft 

corals (sea fans and sea rods) are particularly visible on many reefs. Various types of seaweed and 

algae are also important. Some of algae produce 

limestone structures that add to the overall reef 

structure. Fishes and many other types of animals 

take advantage of shelter provided by the reef, and 

feed on algae and bacteria that grow on surfaces 

within the reef.

Most reef-building corals also contain algae that 

live inside the soft tissue of the polyp. These 

algae are called zooxanthellae (pronounced 

“zoh-zan-THELL-ee”), and like other algae are 

able to use energy from the sun to make food. So 

the corals and algae have a relationship that is 

called “mutualistic.” This means that the coral 

and algae both benefit from the relationship: The 

coral gives the algae a protected environment 

and chemicals the algae need to make food. In 

return, the algae provide the coral with food, 

oxygen and help remove wastes from the coral. 

This relationship allows corals to grow in waters 

that do not have much food available. 

Besides providing corals with food, zooxanthellae are also responsible for the bright colors of 

many corals. When corals are stressed, particularly by high temperature, the polyps lose their 

zooxanthellae and the coral colony becomes 

completely white. This is often called “coral 

bleaching.” Coral polyps can live for a short period of time without zooxanthellae, but if bleaching lasts too long the coral may die.

A colony of star coral. Courtesy Commander William Harrigan, 

NOAA Corps (ret.), Florida Keys National Marine Sanctuary

What is a Coral Reef?
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Coral reefs face numerous hazards and 

threats. Among these are:

Excessive Fishing – Many coral reefs have 

very few fishes because they have been 

captured for food or aquariums. In 

healthy reef ecosystems, fishes graze 

on algae. Without the fishes, algae can 

grow rapidly and smother coral polyps. 

Destruction of Habitats – Some fishing 

methods destroy living reefs. Bottom 

trawling is extremely destructive. In 

some countries, fishermen use dynamite to 

stun fish, which also kills corals and damages 

the reef structure.

Invasive Species – Plants and animals that do not 

naturally live on reefs can damage the reef 

ecosystem. Some invasive seaweeds grow 

rapidly and smother reef-building corals.

“The Rise of Slime” – Many reefs are becoming 

overgrown with marine algae and films of 

bacteria. Part of the problem is pollution. 

In the Gulf of Mexico, for example, fertilizer 

pollution causes excessive growth of algae 

that is responsible for a “dead zone” the size 

of New Jersey. Habitat destruction, overfishing, and pollution also kill natural filters like 

oysters and sponges that normally help clean 

the water.

The 3RD Global Coral Bleaching Event 2014-2017 

This is by far the longest and most widespread event in recorded history. In 1998, 

a huge underwater heatwave killed 16% 

of the corals on reefs around the world. 

Triggered by the El Niño of that year, it 

was declared the first major global coral 

bleaching event. The second global bleaching event that struck was triggered by the 

El Niño of 2010. The US National Oceanic & 

Atmospheric Administration (NOAA) announced the third global bleaching event 

in October 2015 and it has already become 

the longest event recorded, impacting some 

reefs in consecutive years.

The new phenomenon of global coral bleaching events is caused by ocean 

warming (93% of climate change heat is 

absorbed by the ocean). Corals are unable 

to cope with today’s prolonged peaks in 

temperatures – they simply haven’t been 

able to adapt to the higher base temperatures of the ocean. Although reefs 

represent less than 0.1 percent of the 

world’s ocean floor, they help support 

approximately 25 percent of all marine 

species. As a result, the livelihoods of 

500 million people and income worth 

over $30 billion are at stake.

The two previous events caught us relatively unprepared. The world simply didn’t have 

the technology, understanding or teams in 

place to reveal and record them properly. 

This year is different—sponsored by an 

insurance company interested in the risk 

resulting from ocean warming, the XL Catlin 

Seaview Survey, running off predictions issued by NOAA’s Coral Reef Watch programme 

(which have proven to be accurate), has 

been able to respond quickly. A major global bleaching event is considered one of the 

most visual indicators of climate change. 

Working together with science partners 

around the world, these free resources have 

been developed to help you research and 

communicate this important issue, and to 

ensure this event doesn’t stay out of sight 

and out of mind.

www.globalcoralbleaching.org/#overview

Why are Coral Reefs in Trouble?

The Death of a Coral Reef. This image shows the same reef in 

American Samoa before, during, and after a coral bleaching event. 

Photographed by The Ocean Agency / XL Catlin Seaview Survey / 

Richard Vevers.
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Why do corals matter? 

A coral reef is like an oasis in a desert. Corals provide 

both food and shelter for a staggering amount of 

marine life. Although coral reef ecosystems represent 

less than 0.1% of the area of the ocean, approximately 25% of all marine species relies on them. They are 

especially important as a nursery for juvenile fish until they are large enough to venture into open-ocean. 

Losing a coral reef can have a dramatic impact on 

local food,fisheries and livihoods. About 500 million 

people globally depend on such fisheries.

What is coral bleaching? 

Coral bleaching is the process by which corals lose 

their colouration and turn a ghostly white. This 

happens when they become overly stressed especially 

when exposed to warmer than normal temperatures 

and excessive sunlight (normally over 4-6 weeks).

What happens when corals bleach? 

When corals bleach they are actually expelling the 

brown algae that they grow within their body tissues. 

Corals expel algae because high temperatures cause 

the algae to produce toxic compounds. The expulsion 

of algae makes the corals appear a brilliant white—

which is due to skeletons being visible through their 

translucent coral tissue.

How often does coral bleaching occur? 

Bleaching is becoming increasingly common throughout the coral reef regions of the world as a direct 

result of warming oceans. Nowadays there is at least 

some limited coral bleaching reported each year especially during summer months, although the major, 

global events that span multiple oceans are usually 

associated with natural variability (e.g. El Niño conditions) building on top of seas that ar now warmer 

because of climate change. 

What is the connection between bleaching and climate 

change?

Coral bleaching is one of the most visual indicators of 

thermal stress due to climate change. It is a phenomenon caused by ocean warming. The oceans have 

absorbed 93% of the heat from climate change and 

are now significantly warmer than they were 50 years 

ago. The heat that is causing reefs to turn white represents the momentum of climate change—it will increasingly impact our weather, climate and rainfall for 

decades to come until a new equilibrium is reached. 

This hidden energy could also trigger runaway heating 

if the ocean’s methane deposits are released. It is 

why coral reefs are often referred to as “the canary in 

the coalmine.”

What is Mass or Global Coral Bleaching? 

Mass coral bleaching is where whole reef systems 

bleach and not just a few individual corals. This was 

first recorded in 1979. It is thought that a tipping 

point was reached around that time when the shortterm temperatures that normally accompany El Niño 

events began to exceed the temperatures that corals 

could tolerate.

How damaging are mass bleaching events? 

Mass bleaching events can be extremely damaging. A 

reef can turn from a coral dominated reef to an algae 

dominated reef in the space of a few months – a process that can take decades or longer to reverse. The 

Galapagos Islands was one of the first places where 

mass bleaching and mortality was first documented. 

the reefs there lost over 95% of their coral during the 

1982 event. 

Why is coral bleaching associated with El Niño? 

El Niño events result in higher than normal ocean 

temperatures in large parts of the world. This causes 

higher levels of stress on coral reefs. During the warm 

season, the higher than normal ocean temperature, 

combined with additional seasonal heating and sunlight, is often enough to now cause corals to bleach.

Does bleaching only occur when there is an El Niño? 

Major global events have only happened in El Niño 

years to date, however the baseline temperature of 

the ocean is now high enough that we see some mass 

bleaching every year. It is now only a matter of time 

before we have a global event that is not triggered in 

an El Niño year.

Can anything be done to reduce the risk of corals 

bleaching?

The coral’s ability to recover often depends on how 

healthy it was before the event. Coral reefs can be 

‘prepared’ for bleaching events by ensuring local 

stressors, such as overfishing and pollution, are minimised. 

How does the XL Catlin Seaview Survey help? 

The XL Catlin Seaview Survey team is conducting 

the most extensive visual and scientific survey of 

the world’s coral reefs. The Survey’s images are are 

available for expert insight and comment on corals, 

bleaching and ocean change.

Coral Bleaching: Essential Facts

Coral bleaching in the Maldives captured by The Ocean Agency / XL 

Catlin Seaview Survey in May 2016

This Essential Guide to Coral Bleaching was prepared by Professor Ove-Hoegh-Guldberg, XL Catlin Seaview Survey’s Chief Scientist and 

Director of the Global Change Institute at the University of Queensland, Australia. www.globalcoralbleaching.org/#essential-facts