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Flashcards in L15 Deck (30):

what is a coral reef

a coral reef is an organically constructed, wave-resistant, rock-like structure created by carbonate-secreting organisms.


what is an algal ridge

The algal ridge occurs on the reef’s windward side and endures the pounding waves.


what is the buttress zone

The buttress zone is the reef slope extending down from the algal ridge.


what does the buttress zone consist of

It consists of alternating coral-capped ridges, channels, and furrows.


why is the buttress zone shaped the way it is

The buttress zone’s irregular surface disrupts the swell and dissipates wave energy.


what is the reef face

The reef face extends downward from the buttress zone and usually is devoid of living colonial corals because insufficient light reaches this depth.


what is the reef terrace, when is it exposed and what plants flourish here

4. The reef terrace is located landward of the algal ridge and lies at mean water level
it is exposed at low tide and encrusting algae flourish here


what happens at the backside of the reef terrace

grades into a shallow lagoon that is rarely deeper than 50 m


what grows on the lagoon

Numerous small organic knolls, called patch reefs, grow on the lagoon floor.


explain how the shape of the coral masses reflect the environments they live in for the :
algal ridge
butress zone
and quiter areas of the reef

a. On the wave-pounded algal ridge, corals form thin encrusting sheets.
b. In the buttress zone, corals form massive branching colonies or compact, durable mounds.
c. In the deeper, quieter areas of the reef, the corals are either delicately branching or thin, waferlike forms.


describe the 3 stages of reef development

1. Fringe reefs form limestone shorelines around islands or along continents and are the earliest stage of reef development.
2. As the land is progressively submerged and the coral grows upward, an expanding shallow lagoon begins to separate the fringe reef from the shoreline as the reef is transformed into a barrier reef.
3. In the final stage, the land vanishes below the sea and the reef forms an atoll, a ring of coral islands that surround a shallow lagoon.


what is he latin name for where corals belong

phylum Cnidaria


what is most of the reef composed of

loose to well-cemented organic debris of carbonate shells and skeletons.


what is the animal of the coral

The animal is the coral polyp. The body of the polyp resembles a sac with tentacles that surround the open end.


what is the corallite

The corallite is the exoskeleton formed by the polyp, and its interior is divided by septa, vertical partitions.


what do corals share a mutual relationship with



where do the zooathanallae live and what percentage of body weight do they make up

in the skin of the polyp and comprise of 75% of the polyps weight


what does the coral do for the algae

a. The coral provides protection for the algae and supplies it with nutrients and carbon dioxide from the polyp’s metabolic wastes.


what does the algae do for the coral

b. In turn, the algae supply the coral with oxygen and food.


what kind of relationship is it between the coral and the algae



what are the 2 types of coral

solitary or colonial


describe solitary corals

a. Solitary corals, called ahermatypic corals, lack zooxanthallae and can live at any depth or water temperature.


describe colonial corals

b. By contrast, colonial corals, called hermatypic corals, have zooxanthallae and therefore can only live in the photic zone where water temperatures are above 18oC.


what are the ideal ecological conditions for hermatypic corals

1. The ideal ecological condition for hermatypic corals is 20 °C, normal marine salinity water that is clear and is no deeper than 30 m.


where are coral reefs located and why

2. Because of temperature restrictions, coral reefs are more abundant on the west side of ocean basins where warm equatorial currents flow poleward from the low latitudes.


where cant corals survive

Corals cannot survive in fresh, brackish water or highly turbid water.


what kind of water do corals thrive in

7. Corals do best in nutrient-poor water, because they are easily outcompeted by benthonic filter feeders in nutrient-rich water where phytoplankton are abundant or by the growth of seaweeds that overgrow the coral polyps and kill them


how is ocean acidification a threat to coral reefs

Ocean acidification – rising levels of atmospheric CO2 absorbed by the ocean result in the ocean becoming more acidic as CO2 is converted to carbonic acid when it reacts with H2O. Lowers the aragonite saturation state of the ocean in the surface waters, makes it more difficult for organisms that make aragonitic shells to biomineralize.


how is coral bleaching a threat to coral reefs

Coral bleaching - Coral reefs are highly susceptible to changes in temperature, an increase of between 0.5-1.0°C in the ambient seawater can stimulate higher rates of photosynthesis in the symbiotic zooxanthellae that live within the coral. This results in a cellular build up of oxygen that is toxic to the coral and the corals respond by expelling their symbiotic algae from their gastrodermal cells, which causes their tissue to whiten or “bleach”.


list 6 other modern threats to coral reefs

Local pollution
Inputs of nutrients from sewage or mariculture
Inputs of sediment from agricultural or other activities
Too many tourists swimming on reefs
Disease and algal blooms