1. Coral Reefs
2. Coral Requirements for Survival
3. Coral Reef Development
4. Types of Coral Reefs
5. Coral Reef Habitats
6. Coral Reef Ecology

Coral Reef

1. The term coral reef does not refer to any single species of plant or animal but to an integrated community, a functioning assemblage of a large variety of organisms.

Reef Inhabitants

1. Reefs contain colorful sponges, anemones, urchins, plume worms, feather stars and other invertebrates, and a myriad of Walt-Disney looking fishes.

Diversity

1. Coral communities are the most diverse and most beautiful on Earth.

Coral Dominants

1. The name coral community is a tribute to the abundance and importance of corals in these communities.

Corals Need

1. Warm Temperatures (tropical location)
2. Light (shallow water)
3. Low turbidity
4. Low sedimentation
5. Solid substrate
6. Normal salinity

Coral Colonies

1. Corals are sessile animal colonies that are capable of extracting calcium from seawater and depositing it as calcium carbonate in their skeletons.

Growth and Reproduction

1. Colonies grow larger adding new polyps by asexual budding.
2. New colonies develop from sexually produced planula larvae.

Reef Structure

1. Coral skeletons provide structure, "housing" many other reef inhabitants and making corals important members of the community.
2. In this sense they serve a role that is similar to that of plants in terrestrial communities.

Constructive Forces

1. Coral skeletons accumulate and are bound together by encrusting coralline algae and natural cements to form a base on which coral growth continues.

Erosive Forces

1. Erosion by waves and by organisms such as parrotfish, urchins, sponges and boring mussels and worms breakdown corals and reef rock.

Sediment Formation

1. Erosion creates sand and limestone fragments which are moved by waves and currents to surrounding areas including the shore.

Erosion by Humans

1. Recently, erosion by humans has become a significant factor. This includes improper snorkeling and diving techniques and indiscriminant boat anchoring.

Balance of Forces

1. Their is a balance of constructive and destructive factors.
2. Coral growth & cementation vs erosion & sediment formation

Reef Formation

1. If materials accumulate faster than they are destroyed then, slowly this accumulation forms a remarkable, self-repairing, wave resistant barrier that protects the shoreline.

Age

1. Reefs are thousands to hundreds of thousands of years old.

Types of Reefs

1. Fringing Reef: borders the shore (ex. Virgin Island Reefs)
2. Bank Barrier Reef: found close to shore (ex. Jamaican Reefs)
3. Barrier Reef: found far offshore (ex. Belizian Reefs)
4. Atolls: ring-shape of low islands (ex. Lighthouse Reef, Belize)

Reef Evolution

1. Darwin suggested that reef morphology evolves.
2. If reef growth keeps pace with the subsidence of islands then the following sequence could occur:
3. fringing-->bank barrier-->barrier or atoll
4. Rising sea level instead of island subsidence could lead to the same sequence of development

Reef Stratification

1. The interaction between corals and the physical environment results in specific reef formations.
2. The reef can be divided into zones based on biotic and abiotic characteristics.

Lagoon

1. Shallow subtidal, alot of sunlight, protected from waves and sediment covered.
2. Seagrass, burrowing sea cucumbers, sea urchins, ghost shrimp, clams, and conchs.

Back Reef or Reef Flat

1. Seaward portion of the lagoon, very shallow subtidal, intense sunlight, protected from waves and nearly level.
2. High diversity of corals (brain and boulder corals), sea urchins and sea cucumbers

Breaker Zone

1. Very shallow subtidal to intertidal, very intense sunlight, very heavy surf and abundant surge channels.
2. Robust branching corals (elkhorn and staghorn corals) and coralline algae.

Mixed and Buttress Zones

1. 10 to 15 m deep, alot of sunlight, and surf.
2. Spur and groove formation (buttress zone)
3. Very high diversity of corals (brain, boulder, finger, pillar & hill corals). Frequented by large, cruising, carnivorous fish.

Fore Reef

1. 15 to 50 m deep, little light, alot of sediment, steeply sloping.
2. Pinnacle, hillock and haystack formations separated by stretches of sand.
3. Skirted and table corals (boulder, lettuce and fungus corals).

Reef Wall

1. 50 to 150 m deep, very little light, vertical slope.
2. Hard corals are smaller and flatter, sponges and soft corals (black coral) are abundant

Coral Reef Ecosystems

1. Most living systems, including coral reefs, depend upon sunlight energy and chemical nutrients to maintain life.
2. In the tropics, where coral reefs are located, there is plenty of sunlight and blue waters.

Tropical Seas

1. "Blue is the color of the desert regions of the ocean", Wust
2. Tropical ocean waters have very low levels of nutrients. Therefore, they do not contain much phytoplankton which acts as the base of the food chain in the nutrient rich temperate waters.

Low Oceanic Productivity

1. Open Tropical Oceans are
2. low in nutrients and have
3. a productivity of up to
4. 50 grams carbon / square meter /year

High Reef Productivity

1. Growth is luxuriant with a primary productivity of up to 5,000 grams carbon / square meter /year or 100 times greater than the seas in which they are found.
2. This is equivalent to farmland under modern intensive cultivation.

Nutrients and Reefs

1. Most of the scarce nutrients that are available to coral reefs come from the islands whose shores they grow upon.
2. It is produced on the land and discharged by rivers.

Recycling on Reefs

1. Since nutrients are scarce the reef ecosystem must take up and tightly recycle them as a precious resource and prevent their loss.

Reef Producers

1. Most of the energy and nutrients entering the reef system are first incorporated by benthic algae and not phytoplankton.
2. The amount of algal tissue on the reef is much greater than in the surrounding ocean.

Reef Algae

1. These algae are of two sorts: macroalgae which grows on reef surfaces and microalgae which grows inside of the coral polyps themselves.

Reef Herbivores

1. The macroalgae is greedily eaten by fishes and urchins and is an important component of the reef food web.

Symbiotic Algae

1. Of even greater importance is the microalgae called Symbiodinium microadriaticum or zooxanthellae that is symbiotic in coral tissues.
2. They photosynthesize and release food to the corals.
3. The corals in turn provide nutrients to the zooxanthellae.

Tight Recycling

1. Very little Nitrogen and Phosphorus is lost from corals.
2. Instead of loosing these minerals to the water in waste materials the zooxanthellae remove them from the coral polyps and use them.

Corals as Autotrophs

1. Corals, by the action of zooxanthellae, can produce food from carbon dioxide, water and minerals using sunlight as a source of energy in the same way plants do.
2. Photosynthesis provides about 90% of the corals nutritional needs

Corals as Carnivores

1. Corals also kill and eat zooplankton which provides them and their zooxanthellae with a supply of minerals such as nitrogen and phosphorus.