Coral reefsCoral reefs

Basic structureBasic structure

The ability of coral to build a massive The ability of coral to build a massive wave-resistant structure is crucial to wave-resistant structure is crucial to the survival of many of the animal the survival of many of the animal and plant communities. and plant communities.

Major structural and architectural Major structural and architectural feature of a living reef is feature of a living reef is a coral a coral embankment reaching to just embankment reaching to just below the surface of the water.below the surface of the water.

Basic structureBasic structure Hundreds of species of encrusting organisms Hundreds of species of encrusting organisms

cover the surface of a reef and bind the cover the surface of a reef and bind the coral branches together.coral branches together.

Space to grow is one of the major limiting Space to grow is one of the major limiting factors on the reef, so any scar put in the factors on the reef, so any scar put in the coral by a careless fin or break of the coral coral by a careless fin or break of the coral will be quickly taken over by a boring will be quickly taken over by a boring sponge or bivalve mollusc and may signal sponge or bivalve mollusc and may signal the death of the entire coral colony. the death of the entire coral colony. Be Be careful!careful!

Basic structureBasic structure Built of skeletons of tiny Built of skeletons of tiny

marine invertebrate marine invertebrate organisms.  Animals organisms.  Animals themselves tiny, but calcium themselves tiny, but calcium carbonate skeletons build up carbonate skeletons build up and can be extremely strong.  and can be extremely strong.  Corals die, but reef remains. Corals die, but reef remains.

Many organisms add to reef Many organisms add to reef structure including algae, structure including algae, molluscs, sponges and molluscs, sponges and worms.  Algae extremely worms.  Algae extremely important. important.

While reefs can last for While reefs can last for millions of years, the living millions of years, the living surface is extremely fragile surface is extremely fragile and easily damaged.  and easily damaged. 

ValueValue TourismTourism.  Reefs are beautiful .  Reefs are beautiful

and interesting.  Bring billions and interesting.  Bring billions each year.  U.S. gets nearly 2 each year.  U.S. gets nearly 2 billion a year from reef-billion a year from reef-visiting tourists in Hawaii and visiting tourists in Hawaii and Florida keys.  Imagine how Florida keys.  Imagine how important to developing important to developing nations. nations.

Food source.Food source.  Can provide   Can provide 10% of world's supply of fish, 10% of world's supply of fish, molluscs and crustaceans.  molluscs and crustaceans.  This is sustainable.  (approx This is sustainable.  (approx 70 million to U.S.). 70 million to U.S.).

ValueValueComplex ecosystem which supports Complex ecosystem which supports

species diversityspecies diversity. .  Habitats for many organisms.  Habitats for many organisms.  Diverse environment in relatively Diverse environment in relatively

small area.  Can have organisms small area.  Can have organisms adapted to wave action, those adapted to wave action, those that survive in sandy areas, that survive in sandy areas, homes for organisms that do not homes for organisms that do not move (sessile), mangrove move (sessile), mangrove organisms, and clingers to rocks organisms, and clingers to rocks on rocky shores. on rocky shores.

Coral reefs contain 22 of the 23 Coral reefs contain 22 of the 23 animal phyla found on the planet. animal phyla found on the planet. Symbiotic relationships are Symbiotic relationships are common.common.

Act as wave barriers and protect Act as wave barriers and protect shorelines. shorelines. Pictures from: http://state-of-coast.noaa.gov/bulletins/html/crf_08/national.html 

Types of reefsTypes of reefsFringing reefs and bank barrier Fringing reefs and bank barrier

reefsreefs     In a fringing reef the In a fringing reef the coral projects from coral projects from the rocky shore and the rocky shore and the reef remains the reef remains attached to the land. attached to the land.

There is There is no no lagoonlagoon between the reef and the between the reef and the land mass. land mass. The corals are highly varied and often there is no The corals are highly varied and often there is no dominant type. Surrounding it are patch reefs dominant type. Surrounding it are patch reefs composed of a few scattered coralscomposed of a few scattered corals

Fringing reefFringing reef

““An aerial view of a shallow- water, Caribbean An aerial view of a shallow- water, Caribbean fringing reef. Notice the "spur and groove" fringing reef. Notice the "spur and groove" configurations caused by alternating coral configurations caused by alternating coral buttresses and channels. The lighter band buttresses and channels. The lighter band close to shore denotes a rubble/sand zone." close to shore denotes a rubble/sand zone."

Bank barrier reefBank barrier reef Fringing reefs can gradually shade into Fringing reefs can gradually shade into

bank barrier reefs typical of the Caribbean.bank barrier reefs typical of the Caribbean. They have platforms that are much less They have platforms that are much less

extensive and are extensive and are much closer to the much closer to the shoreshore than the ancient barrier reefs of the than the ancient barrier reefs of the Pacific and Pacific and lagoons that are much lagoons that are much shallower.shallower.

Fall between fringing and true barrier reefs.Fall between fringing and true barrier reefs. Atlantic reefs are less than 20,000 years Atlantic reefs are less than 20,000 years

old.old.

Bank barrier reefBank barrier reef Fringing reefs can gradually shade into bank Fringing reefs can gradually shade into bank

barrier reefs typical of the Caribbean.barrier reefs typical of the Caribbean. They have platforms that are much less They have platforms that are much less

extensive and are extensive and are much closer to the much closer to the shoreshore than the ancient barrier reefs of the than the ancient barrier reefs of the Pacific and Pacific and lagoons that are much shallowerlagoons that are much shallower..

The bank barrier reefs in the Atlantic are less The bank barrier reefs in the Atlantic are less than 20,000 yearsthan 20,000 years old, while the Pacific reefs old, while the Pacific reefs are hundreds of thousands of years old. are hundreds of thousands of years old. How can you explain this discrepancy?How can you explain this discrepancy?

Barrier reefsBarrier reefs A barrier reef is a coral reef A barrier reef is a coral reef separated separated

from the land mass by a large lagoonfrom the land mass by a large lagoon with comparatively deep water. with comparatively deep water. Barrier reefs occur in association with Barrier reefs occur in association with continental land masses. continental land masses.

Reefs keep growing out to sea. Reefs keep growing out to sea. why?why? Great rear reef of Australia extends for Great rear reef of Australia extends for

1200 mile. Second-largest is off 1200 mile. Second-largest is off Yucatan coast of Mexico and Belize.Yucatan coast of Mexico and Belize.

Barrier reefsBarrier reefs Barrier reefs grow because of Barrier reefs grow because of

gradual sinking of the land on gradual sinking of the land on which they sit or because of which they sit or because of rising ocean levels.rising ocean levels.

Caribbean barrier reef Caribbean barrier reef probably grew due to rising probably grew due to rising ocean levels.ocean levels.

Barrier reefBarrier reef

AtollAtoll

    An atoll is an isolated ring of coral An atoll is an isolated ring of coral islands and reefs that nearly, or islands and reefs that nearly, or entirely, enclose a lagoon. entirely, enclose a lagoon.

Parts of the reef may stick out of the water as coral islands.  There are over 300 atolls in the Indo-Pacific.  

AtollsAtolls Develop as a volcanic island slowly Develop as a volcanic island slowly

sinks due to its weight and the sinks due to its weight and the fringing reefs on its shore gradually fringing reefs on its shore gradually become barrier reefs as water gets become barrier reefs as water gets between the reef and the sinking between the reef and the sinking island shore.  island shore. 

Finally have the ring. Darwin Finally have the ring. Darwin developed this theory.  Relates all 3 developed this theory.  Relates all 3 types of reef.  types of reef.  How would you show How would you show that Darwin was correct?that Darwin was correct?

Jamaican reefJamaican reef

Back reef;this the reef Back reef;this the reef shore zone. shore zone. Area is protected from the surf and is dotted Area is protected from the surf and is dotted

with isolated coral heads. with isolated coral heads. Turtle grass (Turtle grass (Thalassia testudinumThalassia testudinum ) harbors ) harbors

its own community of sea urchin conchs etc. its own community of sea urchin conchs etc. This is the first place to snorkel. See Kaplan This is the first place to snorkel. See Kaplan for thorough descriptions of the organisms to for thorough descriptions of the organisms to be found in each area of the reef.be found in each area of the reef.

The reef crestThe reef crest

In the protected rear zone of the In the protected rear zone of the back reef you’ll find boulder corals back reef you’ll find boulder corals and those that tend to form large and those that tend to form large and massive hands such as the brain and massive hands such as the brain corals.corals.

In wavy areas you will see gorgonian In wavy areas you will see gorgonian corals.corals.

Reef flatReef flat

This zone is filled with rubble from This zone is filled with rubble from broken corals. broken corals.

The water can be quite shallow here The water can be quite shallow here so be careful when snorkeling. It is so be careful when snorkeling. It is easy to get cut or stung.easy to get cut or stung.

Buttress zoneButtress zone

A favorite snorkel for our students.A favorite snorkel for our students. Swim into an over the sandy Swim into an over the sandy

channels between the massive channels between the massive buttresses of boulder coral.buttresses of boulder coral.

Be sure to read Kaplan’s wonderful Be sure to read Kaplan’s wonderful description of this area before we go description of this area before we go so you will know what to look for.so you will know what to look for.