Coral Reefs

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Coral Reefs  Empty Coral Reefs

Post  Sarah Marti Roy on Sun Oct 19, 2014 7:42 pm

Global Distribution:
The Indonesian/Philippines archipelago has the world’s greatest concentration of reefs and the greatest coral diversity. Other area of reef concentration are the Great Barrier Reef of Australia, the Red Sea and the Caribbean, the latter having a much lower diversity than all major Indo-Pacific regions.

Types of Coral Reefs:
fringing reefs: Fringing reefs are reefs that grow directly from a shore, there is no lagoon between the reef and shore.
barrier reefs: -Barrier reefs are linear reefs that parallel a shore, but are well-separated from it by an expansive lagoon (back reef).
atolls: An atoll is a roughly circular oceanic reef surrounding a large (and often deep) central lagoon.

It’s structure:
(1) Back Reef (Lagoon): -For linear reefs (fringing and barrier), the back reef (aka "lagoon") lies between the reef crest and the shore. The lagoons of atolls are centrally located and nearly completely surrounded by the reef.
2) Reef Crest: The reef crest is the shallowest and narrowest of the 3 zones. It lies between the shoreward lagoon and the seaward fore reef.
(3) Fore Reef ("Reef Face”): The fore reef zone (also often called the "reef face") is the outermost (most seaward) of the three zones. It begins at the outer margin of the reef crest and extends to the lower depth limits of coral growth. This zone contains the greatest mass and diversity of hard corals and reef fishes found in the entire coral reef biome.

The term "coral reef plants" is generally used to refer to all photosynthetic life forms (other than bacteria). Two sub-divisions; the "flowering plants" (angiosperms) and the "algae". However, readers should be aware that the "algae" are no longer considered to be "plants" (part of the Kingdom Plantae) by modern biologists.

Flowering plants: Mangroves and seagrasses are two the only two types of flowering plants (angiosperms). Both groups are capable of rapid growth and high production rates, and thus of making a substantial contribution to the food webs by trapping suspended sediments and slowing water movement these plants also benefit by reducing sediment loads in the water.

Algae: A variety of algae is always present in coral reef, a few types are essential to the survival of corals and the formation of coral reefs. Were once classified as "plants", but that is no longer the case.
Green algae
Red algae
Brown “algae"
Microscopic Reef Algae:
Benthic diatoms: providing their animal host with vital nutrients produced through photosynthesis.
Zooxanthellae: provide much of the primary production that occurs within coral reef ecosystems.

Those that feed mainly or entirely on plant material:

  • Parrotfishes

those that prey upon small animal plankton (zooplankton):

  • Open Water Plankton Feeders (damselfishes, wrasses, snappers, sea basses, and surgeonfishes.)
    Benthic Planktivores
    Nocturnal Planktivores (cardinalfishe, squirrelfishes and soldierfishes.)

Benthic Carnivores
Fishes that prey on a variety of animals living on or near the sea floor:

  • Butterflyfishes
    Triggerfishes (filefishes, trunkfishes, and puffers)
    grunts and snappers

Those that prey mainly or entirely upon other fishes:

  • jacks (Carangidae, pictured left), mackerels, and many sharks.
    rogfishes, lizardfishes (pictured left), flatfishes, groupers, and scorpionfishes.
    barracudas, needlefishes, and trumpetfishes

Other Animals:
Two major groups of animals inhabit coral reefs: animals with backbones (called vertebrates) and those without these structures (called invertebrates).

The vertebrate groups so included are: (1) Sea Snakes, (2) Sea Turtles, (3) Dugongs and Manatees (4) some sharks and dolphins. A few other types of vertebrate animals may occasionally wander into coral reef areas, but these "visitors" are not considered community members.

Invertebrates (animals without "backbones"). Invertebrates are the primary builders of coral reefs.(1) Corals, (2) Sponges, (3) Echinoderms, (4) Mollusks, and (5) Crustaceans.
Corals: Corals belong to a group of invertebrate animals called cnidarians. Cnidarians are characterized by a circular body enclosing a simple gut surrounded by tentacles bearing specialized stinging cells used for defense and/or the capture of prey.

Sponges: are primitive, sedentary animals that filter feed on tiny food particles carried in the water sweeping over them. Coral reef sponges commonly exhibit one of three different body forms.

  • Vase sponges rise from the reef substrate as irregular, somewhat spheroid structures with large central cavities
    Tube sponges exhibit a branched body form.
    Encrusting sponges form a comparatively thin but often expansive layer atop reef substrates.
    Echinoderms: The name "Echinoderm" literally means "spiny-skinned", a trait that shared by all members of the group.
    Sea stars (Class Asteroida)
    Sea Urchins (Class Echinoidea)

Coral reef mollusks are mainly benthic (bottom dwelling) invertebrates, but there are a few open water swimmers included as well. Three classes of mollusks are common in coral reef ecosystems:
• Gastropods (snails, chitons, nudibranchs)
• Bivalves (clams, mussels, scallops)
• Cephalopods (squid, cuttlefish, octopus)

Coral reef crustaceans include the large, more familiar animals such as shrimps, lobsters, and crabs, as well as many smaller or cryptic types like amphipods, stomatopods, and copepods.

  • Spiny Lobsters

-Warmer water temperatures brought on by climate change stress corals because they are very sensitive to changes in temperature. If water temperatures stay higher than usual for many weeks, the zooxanthellae they depend on for some of their food leave their tissue. Without zooxanthellae, corals turn white because zooxanthellae give corals their color. White, unhealthy corals are called bleached. Bleached corals are weak and less able to combat disease.

Abiotic Factors:
-latitude: They are found in clear tropical ocean water usually between 30N to 30S latitudes
-temperature: The water temperature must be between 20-25C
-salinity: Coral are formed only in saline water with almost 27ppp (parts per million).
-depth: Coral reef can form to depth of 90 meters since at this depth algae can form food through photosynthesis. Corals need saltwater to survive and require a certain balance in the ratio of salt to water. This is why corals don’t live in areas where rivers drain fresh water into the ocean
-Clear water: : Corals need clear water that lets sunlight through; they don’t thrive well when the water is opaque. Sediment and plankton can cloud water, which decreases the amount of sunlight that reaches the zooxanthellae.Corals are not found near mouth of river where lots of sediments are unloaded into ocean.
-sunlight: Corals need to grow in shallow water where sunlight can reach them. Corals depend on the zooxanthellae (algae) that grow inside of them for oxygen and other things, and since these algae needs sunlight to survive, corals also need sunlight to survive. Corals rarely develop in water deeper than 165 feet (50 meters).

-Higher sea temperatures from global warming have already caused major coral bleaching events. Bleaching occurs when corals respond to the stress of warmer temperatures by expelling the colorful algae that live within them. Some coral are able to recover, but too often the coral dies, and the entire ecosystem for which it forms the base, virtually disappears.
-Ocean acidification--which occurs when oceans absorb carbon dioxide from the atmosphere--is also a threat to coral. As the oceans become more acidic, the corals' ability to form skeletons through calcification is inhibited, causing their growth to slow. A doubling of atmospheric carbon dioxide will reduce calcification in some corals by as much as 50 percent.
-Sea level rise caused by melting sea ice and thermal expansion of the oceans could also cause problems for some reefs by making them too deep to receive adequate sunlight, another factor important for survival.

Interesting Facts:
-Some species of coral reproduce by coral spawning. This means that in unison and in some cases on one particular night a year, the coral eject large quantities of eggs and sperm into the surrounding water. This always happens at night and just after the full moon. Trillions of eggs and sperm are released all at once. When this occurs, the eggs and sperm fertilize in the water and then if the larvae that grow survive, they settle back to the ocean floor, attach themselves to a hard surface and grow.
-The Great Barrier Reef is the largest coral reef biome located in Australia and it’s visible from outer space.
-They grow at a rate up to 2 cm per year.
-The world's first coral reefs formed about 500 million years ago.
-It is illegal to damage or sell coral.
Coral has venomous tentacles they can stick out to catch prey and they hunt at night.
Sarah Marti Roy
Sarah Marti Roy
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Post  Gloria H. on Thu Oct 23, 2014 11:50 am

wow seems like you know a lot about coral reefs, the interesting facts are crazy, and how the temperature is it changes a lit tiny bit it could kill the coral!!

Gloria H.

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Coral Reefs  Empty Good Job

Post  Joshua T on Mon Oct 27, 2014 8:36 am

Due to global warming, coral reefs are becoming endangered. Small changes in the temperature could destroy coral reefs. Another thing, coral reefs are only found around near the equator and it is very rare to see a coral reef under 200 meters.

Joshua T

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Post  CicelyS on Wed Oct 29, 2014 11:38 pm

Do you know if there are a lot of dead coral reefs in the DR? You have such extensive research on the topic, good job!

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Post  Alicia M. on Thu Nov 06, 2014 12:01 pm

woww! Nice information you have there! Coral Reef are really important, and as we know, many of it is dying. This is a sad but true fact, No
Alicia M.
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Post  Mira W. on Wed Nov 12, 2014 11:01 pm

It's really sad, we are basically destroying our own environment. And we know it - but won't do anything to change. I find that to be a very depressing thought ... Amazingly thorough (and long) post! I had no idea corals could be venomous, or that it was illegal to sell them. Awesome job Smile
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