Earth 100 Coral Reefs Exam 1

coral reefs

rock-like structures made of calcium carbonate produced by living organisms

Polyp

The sessile, tubular form of a cnidarian with a mouth and tentacles at one end and a basal disk at the other (radially symmetrical)

1. Home to a huge variety of organisms

2. Breeding and feeding ground for many fish and other organisms

3. Protect shorelines from erosion and flooding

Why are Coral Reefs important?

1. shallow tropical water environments

2. Latitudes 30N - 30S

3. Between 0-100m from surface

4. Temperature: Scleractinian corals can grow at T between 18-40°C -- optimal 23-25oC

Where do coral reefs typically exist?

basal plate or corallite

At the base of the polyp a skeleton is built, called the

cnidocytes

They are cells modified to capture and immobilize prey by injecting poison and firing very rapidly in response to contact

Zooxanthellae

single celled algae, dinoflagellates -- also form red tides, e live in symbiosis with corals, and They live in the coral polyp's surface layer where they perform photosynthesis

Subclass Hexacorallia

members of the class Anthozoa with more six or multiple of six tentacles. This group includes reef-building corals (Scleractinians) and sea anemones

Subclass Octocorallia

members of the class Anthozoa with eight tentacles. ex soft corals, sea fans and sea whip

Hermatypic and Ahermatypic corals

Two types of Scleractinian Corals

Hermatypic corals

- Produce reefs

- Found only in tropical regions

- Have small symbiotic algae called zooxanthellae living in their tissue

Ahermatypic corals

- Do not build reefs

- May not contain zooxanthellae

- Not restricted by water temperature and water quality

cenosarc

a thin layer of soft tissue serving to interconnect adjacent polyps of a coral colony

corals with large polyps & tentacles

What type of coral is less dependent on zooxanthellae?

zooxanthellae

What is the principal source of food for reef-building corals?

Night

When, during an average day, reef-building corals are more actively carrying on predation?

1. zooxanthellae

2. mucus films that trap organisms

3. sharing of food

4. carnivorous using tentacles to capture prey

What are the different ways corals get nutrients?

sexually and asexually

What are the two different ways coral reproduce?

A form of asexual reproduction where a new polyp grows from an adult, it increases size of the colony

What is Budding (gemmation)

a single polyp abandons the colony and settles on a different substrate to create a new colony

What happens in bailout reproduction?

individuals broken from the colony during storms or other situations. The separated individuals can start new colonies

What happens in fragmentation reproduction?

broadcast spawning reproduction (most common)

- Release eggs and sperm into the water where fertilization and development occur

- Only 1 or 2 reproductive cycles/ yr

- Cues to spawning are T, tides, light, etc

brooding reproduction (rare)

- Eggs develop into larvae internally

- Larvae are released, often at night, in response to the lunar cycle

- Up to 12 reproductive cycles/ yr

Coral Triangle

Highest coral diversity in the world: 76% of the world's coral species are present here

1. Salinity: Scleractinian corals are very sensitive to salinity -- most thrive at ~36

2. Sedimentation: Scleractinian corals grow in very clear water -- very little sediments

3. Nutrients: Scleractinian corals live in nutrient-poor waters because High nutrient-levels cause algal growth that can smother corals and reduce light • 4. Moderate water motion: Wave activity lessens sediment accumulation on corals

5. Emersion: corals only tolerate short (~1hr) exposure above sea level

What are the 5 things that can prevent coral from thriving?

1. Very efficient relationship between corals and zooxanthellae

2. High flow rate of water over reef

3. Rapid recycling of nutrients (high levels of bacteria)

Why do Coral reefs have such high productivity in nutrient poor areas?

competition

negative interaction in which different organisms require the same limited resource

Predation

negative interaction in which a predator feeds on its prey

Grazing

type of predation in which a herbivore feeds on plants/algae

exploitative competition

Type of competition used by branching corals to grow more rapidly than encrusting or massive corals

interference competition

Type of competition where Slow-growing massive corals can extend digestive filaments or develop "sweeper tentacles" and kill competing coral species

mesenteric filaments

extensions of the stomach used to kill or devour other coral polyps through a process similar to digestion

sweeper tentacles

the most common defense mechanisms in reef forming corals. They are elongated tentacles (up to 30 cm long) that form the outermost portion of the colony and act as a "patrol" along the periphery

Mutualism

A relationship between two species in which both species benefit (between hermatypic corals and zooxanthellae)

Lagoon

a stretch of salt water separated from the sea by a low sandbank or coral reef.

- Variable depth with channels

- Covered in coral sand

- Nutrients and sediments from the reef front

- Patch reefs or isolated large stands of corals

- Seagrass beds

Back Reef

the inner, land side of a coral reef with less biological activity

→Shallow and closest to shore

→Low energy and high sedimentation

→Fluctuating T and S

→Small patch reefs, sand and seagrass

Reef Flat

The wide and shallow upper surface of a coral reef

→Very shallow and flat

→Poor coral growth

→Exposure at low tides (erosion)

reef crest

The shallow outer edge of the reef slope of a coral reef

→Highest energy zone

→Very intense light levels

→Limited coral growth

→Lots of rubble and sand

→Dominated by coralline algae

Reef Slope

The outer, steep margin of a coral reef

→Optimal coral habitat

→Dominated by reef-building corals

→Most diverse zone

→Different species at different depth

1. Back Reef

2. Lagoon

3. Reef Flat

4. Reef Crest

5. Reef Slope

What are the different reef zones