Coral Reefs
Zones of a Coral Reef
The reef is divided into 3 main areas: the reef flat, the reef crest and the fore reef
The reef flat is the most shallow zone and is closest to the shore. Because it is so shallow this area varies in temperature and salinity. There is not a lot of coral growth here due to the exposure at low tide and changes in temperature and salinity; however, this section supports the most organisms out of the 3 sections. Supported species include a variety of bivalves, worms, crabs, and lobsters.
The reef crest is the highest point of a coral reef. It is a smaller area located between teh reef flat and the fore reef. It can be anywhere from 3 to 55 yards across. This area is often exposed at low tide and must deal with the constant pounding of waves upon its corals. One particular algae, calcareous red algae, dominates this area which is why it is often referred to as an algal ridge. There are few corals that can withstand heavy wave action; therefore, you typically only see short, branching corals like elkhorn coral. Many marine species will seek shelter in the nooks and crannies of the reef's crest.
The fore reef is the area of the reef farthest away from shore (closest to the ocean). Typically, it slopes downward sometimes to great depths (think Finding Nemo's the drop-off). This area has the largest corals because it is an "easier" environment to live in with less wave action. On the slope, corals are more diverse in the shallower areas and species diversity decreases with increased depth. Light availability plays a big part in which corals will flourish with increased depth. The deep fore reef is the "drop off" area at the very edge of the fore reef.
The reef is divided into 3 main areas: the reef flat, the reef crest and the fore reef
The reef flat is the most shallow zone and is closest to the shore. Because it is so shallow this area varies in temperature and salinity. There is not a lot of coral growth here due to the exposure at low tide and changes in temperature and salinity; however, this section supports the most organisms out of the 3 sections. Supported species include a variety of bivalves, worms, crabs, and lobsters.
The reef crest is the highest point of a coral reef. It is a smaller area located between teh reef flat and the fore reef. It can be anywhere from 3 to 55 yards across. This area is often exposed at low tide and must deal with the constant pounding of waves upon its corals. One particular algae, calcareous red algae, dominates this area which is why it is often referred to as an algal ridge. There are few corals that can withstand heavy wave action; therefore, you typically only see short, branching corals like elkhorn coral. Many marine species will seek shelter in the nooks and crannies of the reef's crest.
The fore reef is the area of the reef farthest away from shore (closest to the ocean). Typically, it slopes downward sometimes to great depths (think Finding Nemo's the drop-off). This area has the largest corals because it is an "easier" environment to live in with less wave action. On the slope, corals are more diverse in the shallower areas and species diversity decreases with increased depth. Light availability plays a big part in which corals will flourish with increased depth. The deep fore reef is the "drop off" area at the very edge of the fore reef.
Location
Corals are primarily found in areas where water temperature is between 70 and 86 degrees Fahrenheit and between 30N and 30S (the tropical and subtropical waters). There are a few exceptions with cold water reefs.
Most corals are colonial. This means that the individual corals live together and are connected by tissue. As they build their skeleton coral reefs are formed.
Types of Coral Reefs
Coral reefs are broken down into 3 main categories: Fringing reefs, Barrier reefs, and atolls.
Corals are primarily found in areas where water temperature is between 70 and 86 degrees Fahrenheit and between 30N and 30S (the tropical and subtropical waters). There are a few exceptions with cold water reefs.
Most corals are colonial. This means that the individual corals live together and are connected by tissue. As they build their skeleton coral reefs are formed.
Types of Coral Reefs
Coral reefs are broken down into 3 main categories: Fringing reefs, Barrier reefs, and atolls.
Fringing reefs lie near the shores of islands or continents. This is the most common type of coral reef and are continuous with the land mass. These do best in areas with little rain and low land run off. They are most commonly found in the South Pacific Hawaiian Islands and parts of the Caribbean.
Atolls are large, ring-shaped reefs that have a lagoon in the center. These rest on the tops of underwater volcanoes. Sometimes, parts of these atolls emerge as islands. These islands often consist of coconut trees. These are found in the Indo-Pacific region.
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Barrier reefs are a bit broader (wider) and are farther away from the coast. They are separated from land by a stretch of water that can be up to several miles wide and fairly deep. This stretch of water forms a lagoon. These are most commonly found in the Caribbean and Indo-Pacific areas. |
Types of corals:
There are two main types of coral: hard coral, the major reef-building species; and soft coral, such as whips and sea fans. Hard corals remove calcium from surrounding seawater and use this to create the carbonate structures that form the reefs. There are many different types of corals but we will look at the more common ones: The common names given to many hard corals are indicative of their appearance.
There are two main types of coral: hard coral, the major reef-building species; and soft coral, such as whips and sea fans. Hard corals remove calcium from surrounding seawater and use this to create the carbonate structures that form the reefs. There are many different types of corals but we will look at the more common ones: The common names given to many hard corals are indicative of their appearance.
Finger: inhabit the reef crest, grow extremely slowly, therefore thought to be some of the oldest corals, finger-like branches with porous skeletons. The tips of its branches are usually blunt or flattened,
Brain: generally spherical in shape and have a grooved surface which resembles a brain
Pillar: favors the flat part of the reef, resembles fingers or a cluster of cigars, growing up from the sea floor without any secondary branching (so tube-like), one of the only corals that are often seen feeding during the day
Lettuce: occur in deeper areas, Lettuce Coral appears in large leafy growths (look like a head of lettuce)
Star: living in deeper waters, star corals form plate-like structures that allow more sunlight for the zooxanthaellae. Forms into massive boulders--Its polyps are the size of a human thumb
Elkhorn: usually found in shallow water, considered to be one of the most important reef-building corals in the Caribbean. This species has many large branches. The coral structure closely resembles that of elk/deer antlers
Soft corals are known by common names such as sea fans, sea plumes, sea rods, sea fingers, sea whips, wire corals, black coral and deep-water gorgonians. Generally they are just called gorgonians. They are seen "floating" back and forth with the currents. The majority of these corals are found in relatively shallow areas. Sea fans will try to grow in the path of a current to make capturing food easier.