CORAL AND CORAL REEFS

Coral Reefs• Corals are marine invertebrates, which are animals, in the

phylum Cnidaria.

• Class Anthozoa (Anthos= flower, Zoa= animals) is exclusively

marine, and include sea anemones, stony corals, soft corals, sea

pens, sea fans and sea pansies.

• Anthozoa is the largest taxon of cnidarians; over six thousand solitary

and colonial species

• They typically live in compact colonies of many identical

individual polyps (which are animals as well, just very tiny).

• The group includes the important reef builders that inhabit

tropical oceans and secrete calcium carbonate to form a

hard skeleton.

• Coral polyps are translucent animals that form a living mat

over a calcium carbonate skeleton.

• Stony corals are the corals primarily responsible for laying

the foundations of, and building up, reef structures.

Key Characteristics of a Coral Reef?

• Colorful

• Extremely Diverse Life

• Located in Warm Water

• USUALLY located in Clear Water

• Water is Nutrient Poor

Interesting Facts about the Coral Reefs

• Though coral reefs cover less than 1% of the Earth’s surface, over 25% of all marine fish species find their homes in coral reefs.

• The average growth rate of a coral reef is less than 3 cm per year; hence it takes several years to form a large coral/area of coral

• Coral is an animal related to jellyfish (A Cnidarian)

CORAL

Anatomy of a Coral Reef

-Reefs are made when

each individual coral

organism – or polyp –

secretes a skeleton of

calcium carbonate

-Zooxanthallae (an

algae/protist) will

inhabit the Coral

General Characteristics• Coral polyps are tiny, soft-

bodied organisms related to

sea anemones and jellyfish.

• At their base is a hard,

protective limestone

skeleton called a calicle,

which forms the structure of

coral reefs.

• Reefs begin when a polyp

attaches itself to a rock on

the sea floor, then divides,

or buds, into thousands of

clones.

• Coral reefs are built from the

remains of stony or hard

corals

• Salt water: 34-37 ppt

• Hard substrate to settle on as larvae

• Food

• Oxygen

• NOT A PLANT, A PROTIST

• Sunlight

• Nutrients (nitrogen)

• Warm temperature:~20ºC

• Clear water

• Carbon dioxide

Factors necessary for coral reef formation:

Coral (animals) need: Zooxanthellae (algae)need:

Reef Formation• Reefs cover about 100,000 square miles of the world’s

shallow marine areas

• Located in shallow, tropical waters

• They grow gradually as the organisms that form their

living surfaces multiply, spread, and die, adding their

limestone skeletons to the reef.

• Millions of Stony coral polyps are the marine animals

responsible for building the hardened coral reefs you

see in the ocean

• Reefs are excretions of calcium carbonate produced

by each polyp

• New polyps secrete reef on top of older polyps

Reef Growth Forms

• Hard coral colonies generally exhibit one

of three basic growth forms:

1.Massive

2.Branching

3.Plate-like

1. Massive• These rely on sheer mass, growing into

huge sheet or boulder formations that tend

to make up the bulk of a reef

2. Branching

• These require a small area to anchor

themselves, but branch out into vast, tree-

like colonies

3. Plate-like

• Form flat expanses that overshadow other

corals and monopolize the available light

Zooxanthellae “ZO ZAN THEL I/A”

• Tiny algae that are photosynthetic

organisms live in the tissue of

each coral polyp, millions can live

in just one square inch of the

coral

• Provide a source of food to the

polyps

• Give corals their color

• Example of a mutualistic

symbiotic relationship

• This is why corals need sunlight

to grow

• Receives Food

• Receives Oxygen

• Receives protection

• Receives Carbon Dioxide

Mutualism

Coral (animals) need: Zooxanthellae (algae)need:

Organisms Contributions

• Mollusks and echinoderms add their

skeletal remains

• Grazing and boring organisms break

down coral skeletons into sand

• Coralline Algae bind the sand

Importance of Coral Reefs to the Environment

• The Reefs built by corals provides homes for millions of different species

• Involved in nitrogen fixation provides food to fish

• Photosynthesis of the Zooxanthallae absorbs carbon

• Nursery for different organisms.

Importance of Coral Reefs to Humans

• Coral reefs are widely used in the treatment of cancer, HIV, cardiovascular diseases and Asthma.

• Porous limestone skeletons of the corals have been used in grafting human bones.

• Important source for the fishing industry

• Protect coastlines from storm surges

• Stimulate economy through increasing tourism

Reef Distribution

Coral Reefs are found in all three of Earth’s oceans that have

portions in the tropics. (Pacific, Atlantic, and Indian). They are

scattered randomly, however.

Reef Distribution

• Grow in clear, sunlit,

shallow water

• Average salinity of 36 ppt

• Require warmer water

temperatures, as seen in

tropical and sub-tropical

areas

• Require little or no wave

action

• Little or no sedimentation

from river run-off

• The two main areas of

development that meet

these criteria are the

Indo-Pacific and

Greater Carribean

Belize – Great Blue Hole

Indo-Pacific Region

• Central and South

Pacific Ocean

• Greatest number are

in an area from

southern Phillipines

through western New

Guinea and Indonesia

• Red Sea are is cut off

from large water flow,

so has high number

of endemic species

Greater Caribbean Region

• Tropical, western

Atlantic

• Spans the entire

Caribbean Sea,

Bahamas, and south

Florida

PARTS

OF

REEFS

Parts of a

Reef

Parts of a Reef

• Reef Slope:

– or fore-reef, is the part that

faces the sea.

– The upper parts of the reef

slope are dominated by

branching coral colonies

and intermediate depths

by massive forms.

– These are the areas of the

reef with the greatest

diversity of species.

• Reef Crest

– Narrowest of the reef

zones

– Massive wall that

absorbs the energy of

incoming waves

(makes water calmer

for back reef zone)

• REEF FLAT:

– Shoreward of the reef

crest is the reef flat, a

shallow, relatively flat

expanse of limestone,

sand, and coral

fragments that may

become exposed at

high tide.

– The number of corals

decreases toward the

shore.

• Barrier reefs and

atolls have a final

zone, the lagoon

area.

LAGOON

• a shallow body of water

separated from a larger body

of water by barrier islands or

reefs.

• Lagoons are commonly

divided into coastal lagoons

and atoll lagoons.

• They have also been identified

as occurring on mixed-sand

and gravel coastlines.

• Lagoons are common coastal

features around the world.

Reef Flat and Lagoon Areas

AKA “Back Reef”

• Contains shallow water

habitats for reef species

• Vital role in food web

• Experiences large

temperature and salinity

changes, reduced water

circulation, and

sediment accumulation

• Main Habitats here:

• Patch reefs

• Sand plains

• Seagrass meadows

• Mangrove forests

Types of Reefs &

Importance and Human Impacts

of/to Reefs

Importance of Reefs• Coral reefs provide a buffer, protecting our coasts

from waves, storms, and floods.

• Corals form barriers to protect the shoreline from

waves and storms.

• The coral reef structure buffers shorelines against

waves, storms, and floods, helping to prevent loss

of life, property damage, and erosion.

– Provide protective barrier around islands and

coasts

– Slows down strong currents and waves before it

hits the shore

– Prevent erosion

Importance of Reefs• Create more living biomass than any other marine ecosystem

• provide a habitat, spawning and nursery grounds for

economically important fish species;

• provide jobs and income to local economies from fishing,

recreation, and tourism

• Support more species than any other marine environment

• Possibilities in medicines and science

– induce and ease labor; treat cancer, arthritis, asthma, ulcers,

human bacterial infections, heart disease, viruses, and other

diseases; as well as sources of nutritional supplements,

enzymes, and cosmetics

• Control carbon dioxide levels in ocean water

– The coral polyp turns carbon dioxide in the water into a

limestone shell

Types of Reefs• The basic Coral Reef classification scheme was first

proposed by Charles Darwin

• There are three main types of reefs:

Fringing

Barrier

Atolls• There are two other

reef types:

Patch reefs

Bank reefs

Fringing Reefs

• Occur adjacent to the land,

with little or no separation

from the shore

• They develop through

upward growth of reef-

forming corals on an area of

continental shelf.

• May have a completely

shallow lagoon in some

areas, or no lagoon at all

• Most common reef in the

Greater Carribbean and Red

Sea

• Also surround many South Pacific and

Indian Ocean Islands

• Most susceptible to coastal development,

agriculture, pollution, and other human

activities resulting in sedimentation and

freshwater runoff

Barrier Reefs

• Broader and Separated from land

by a lagoon that can be miles wide

and at least a dozen yards deep

• Usually parallel the shore

• Parts of the reef structure often

protrude above sea level as low-

lying coral islands.

– These develop as wave action deposits

coral fragments broken off from the reef

itself

• Largest reefs develop on the edges

of continental shelves (called “shelf

barrier reefs”

– Great barrier reef, Belize barrier reef

Atolls• Large, ring-shaped reefs,

surrounding a central

lagoon

• found well away from

large landmasses, such

as in the South Pacific

• Usually circular or

horseshoe-shaped

• parts of atolls may

protrude above the

surface forming coral

islands as well.

• Most common in the

Indo-Pacific region

(over 300)

• Rare in Caribbean

(only 10-15)

– Southern Mexico and

Belize

• Can exceed 100

miles in diameter

• Central lagoons can

be several thousand

square miles

ANATOMY OF A REEF

Patch Reefs• Small reefs found within

the lagoons of other reefs

• Usually small, isolated outcrops of coral surrounded by sand and / or seagrasses

• Provide refuge and food for may species of animals and fishes

• patch reefs appear golden brown surrounded by a white halo and seagrass meadows.

Bank Reefs

• Reef structures with no obvious link to a

coastline

• Offshore bank reefs occur seaward of the

patch reefs. Bank reefs are larger than the

patch reefs and are generally linear or semi-

circular in outline.

• Most of the snorkeling and scuba diving takes

place on these reefs

Evolution of the Three Main Reef Types

• As first proposed by Charles Darwin:

• Darwin proposed the three main reef

types are simply different stages in

the geological ‘evolution” of Pacific

oceanic islands.

Darwin’s Theory

• Fringing reefs began to

grow near the shorelines of

new islands when

conditions for growth were

ideal

• As the island began

to gradually subside

into the sea, the coral

was able to grow at

the same rate, and

remained in place at

the sea surface, but

farther from shore.

• It was now a barrier

reef

• Eventually, the island

disappeared below

the sea surface,

leaving only the ring

of coral surrounding it

• It was now an atoll

• Darwin’s theory of “reef evolution” was

verified for the Indo-Pacific reefs in the

early 1950’s

– After analyses of deep core drilling at Bikini

and Eniwetok Atolls

– We now know, however, that in some cases,

the three types can be formed by different

processes as well

Coral Reef Threats

FYI….Did you know…• Coral reefs occupy only 2% of the oceans’ area, but are home to ¼

of all known marine species

• We have already lost 27% of the world's coral reefs. If present rates

of destruction are allowed to continue, 60% of the world's coral reefs

will be destroyed over the next 30 years

• Occupying less than one quarter of 1% of the marine environment,

coral reefs are home to more than 25% of all known marine fish

species

• 58% of the world's coral reefs are potentially threatened by human

activity

• Coral reefs are found in 109 countries; significant reef degradation

has occurred in 93

• More than 80% of the world's shallow reefs are severely over-fished

• Properly managed coral reefs can yield an average of 15 tons of fish and other seafood per square kilometer each year

Human Impacts on Reefs• Coastal and ocean pollution

– Oil slicks, pesticides, chemicals, heavy metals, garbage, etc.

• Poisons coral polyps

– Fertilizer and untreated sewage encourages algae growth

• High concentrations of algae can cover the coral and block sunlight if not kept under control by herbivores

Massive oil slick as seen from satellite photos

Human Impacts on Reefs

• Uncontrolled development of

coasts

– Deforestation

– Dredging and coastal development

• Hotels

• Homes

• harbors

Soil run-off - Hawaii

Runoff from a pipe in

the Virgin Islands,

directly near a reef

Human Impacts on Reefs

• Recreation

– Boat anchors crush

corals and gouge the

reef

– Diving tourism

• Divers and snorklers

sit, stand on, or

handle corals

Human Impacts on Reefs• Collection of corals and organisms

– International seashell and aquarium trades have put

a strain on coral reef ecosystems

– Upsets the balance of the ecosystem

• Market for coral skeletons, shells, sponges and

reef animals for decorations, jewelry, sculptures

• Tropical fish trade

• Coral skeletons are are sold as “live rock”

–Popular in aquariums because of the living

bacteria and algae that acts as a natural

biological filter

Human Impacts on Reefs

• Uncontrolled mining for building materials

Human Impacts on Reefs

• Destructive fishing practices

– Overharvesting of species

can lead to the species’

demise

– Fishing with dynamite,

cyanide, or bleach

– Careless handling of nets,

lines, and lobster traps

can lead to reef damage

– Boating / anchors also

leads to reef damage

• Between 1986 – 1991, ½ of

the coral reefs in the

Philippines were destroyed

by this

Coca-Cola bottle with slightly

burned fuse found around the

Capone Islands, Phillipines

Human Impacts on Reefs• Natural disturbances:

– Hurricanes and tropical storms can strip corals from

miles of reef habitat

Human Impact on Reefs

• Increases in atmospheric carbon dioxide

increases the acidity of the ocean

• Higher ocean acidity makes it harder for

reefs to construct their calcium carbonate

skeletons

The Ocean is a Carbon Sink

What does this mean?

-The Ocean absorbs Carbon Dioxide

Atmospheric

CO2Oceanic

CO2

pHOcean

acidification

Temperature

Coral

Bleaching

What are the effects of too much CO2?

1. Ocean Acidification

2. Coral Bleaching

What is Ocean Acidification?

What is Ocean Acidification?

Normal Conditions

• The Ocean is naturally Basic (pH ~8)

• Calcium Carbonate (CaCO3) present in the water and available for organisms to use for their shells and skeletons

What is Ocean Acidification?

• A decrease in Ocean pH means that there are more H+ ions will react with the Carbonate Ions to form Bicarbonate INSTEAD of Calcium Carbonate

Atmospheric

CO2Oceanic

CO2

pHOcean

acidification

What do you observe?

Ocean Acidification Decrease in Calcium Carbonate

• It DOES NOT mean that the ocean is so acidic that it is dissolving the shells of bivalves and skeleton of corals…yet.

• It DOES mean that there is not enough Calcium Carbonate for these shelled organisms to build their structures

What is Coral Bleaching?

• An increase in CO2 (a greenhouse gas) causes an increase in temperature

• The increase in temperature is an environmental stressor for the Coral

• Other environmental Stressors: pH change and pollution

Atmospheric

CO2Oceanic

CO2

Temperature

Coral

Bleaching

What do you observe?

What is Coral Bleaching?

• As Corals are stressed, they will start to expel and/or actively digest their zooxanthellae

• If the stress is intense, they Corals will expel all their zooxanthellae leading to the bleached look

Effects of Coral Bleaching

• The corals can survive a bleaching episode

• They are animals so they can still eat food to live

BUT

• They are more vulnerable to diseases, infections, and mortality

• Zooxanthellae can be resorbed but will not survive long outside of the coral

Natural Threat: Crown of Thorn

Natural Threat: Crown of Thorns

• When balanced, the Crown of Thorns play an important role of consuming the fast growing coral; therefore, regulating the population and enabling slow growing corals to grow

• Cyclical outbreaks are natural but they have been happening more often than previously

-possibly linked with the warmer waters because the sea star spawn during warmer seasons

Case Studies

• Human Impacts on Coral Reefs

• Crown of Thorns Impact

Coral Bleaching

• Occurs when corals become stressed

– They expel the zooxanthellae living in them

• They lose their color and become whitened

• Can be caused with warmer surface waters (maybe even by 1-2 degrees)

– May have a link to global warming

• Pollution can also be a cause

• Full recovery takes decades

CORAL BLEACHING:

• From 1876-1979 only three bleaching

events were recorded

• whereas 60 are on record from 1980

until 1993

• in 2002 more than 400 events were

recorded

Bleaching can be seen in areas of the Great Barrier Reef

Coral Poisoning

• Very destructive

fishing practice

• A diver sprays

sodium cyanide to

catch a fish

• The poison kills all

corals in the area

Crown of

Thorns Starfish

Coral Reef Diversity

• Healthy reefs can house thousands of species

– Fish

– Invertebrates

– Sponges

– Soft corals

• Every part of a reef is used by some animal

• Mutualism –relationship between two different species where they both benefit

Organisms of a Coral Reef

Corals

Leafy Sea Dragon and Weedy Sea Dragon

Clownfish

Blue Tangs

Parrot Fish

-Eat Coral

with their

strong beaks

-They cannot

digest Coral, so

they pass the

crushed Coral

makes the nice

white sand

Class Cephalopoda (Phylum Mollusca)

• “Head-Foot”

• Intelligent (largest centralized brain of all the invertebrates)

• Soft Bodied

• Sophisticated Eyes (but Colorblind) Visual Predator

• Tentacles with suction cups

• Contain Chromatophorees (color changing cells)

• Contain Iridophores (reflective cells)

• Beak

Cuttlefish

Octopus

Squid

Moray Eels

Gobie fishMandarin fish