Presented By: T.Chailagoaban
What is Coral? An animal belongs to Phylum cnidaria Cnidarians are readily symmetric means they are symmetric all the way around 360 degrees They are built like sacs with a hole in one end that is surrounded by stinging tentacles A corals body is called as coral Polyp Millions of coral polyps together make the structure of coral reef
Anatomy of a Coral Polyp
Anatomy of a coral Few millimeters in diameter They are radially symmetrical with tentacles surrounding a central mouth. The mouth is used to absorb food and expel waste The stomach closes at the base of the polyp The base is formed by a thickened calciferous ring
Coral Symbiosis Symbiosis occurs when two organisms create a union in which each is benefited by the other. Corals live a Symbiotic life Inside the sac of each coral polyp lives an algae called zooxanthellae (zoo-zan zan-thel-y). The algae gives off oxygen and other nutrients that the coral polyp needs to live and in return the polyp gives the algae carbon dioxide and other substances the algae needs
Coral Symbiosis Carbondioxide, nitrite, phosphates Corals Zooxanthalle Oxygen, nutrients, color, glucose, glycerol, and amino acids
Zooxanthelle Zooxanthelle gives the color, oxygen and nutrients to the corals Zooxanthelle
Climate conditions Suitable for Corals Reefs grow in sunny, shallow, clear water. The water must be clear and shallow so that the reef can get lots of sunlight poorly in areas where there is a lot of river runoff due to the freshwater as well as the silt which can cover a reef or muddy water blocking the sunlight The best temperature for coral reefs is between 25 and 31 o C and the best salinity is between 34 and 37 parts per 1000
Growth of a coral The polyp grows by vertical extension of the basal plate forming vertical calices which are occasionally septated to form a new, higher, basal plate Over many generations this extension forms the large calciferous structures of corals and ultimately coral reefs Coral calciferous bands Formation of the calciferous exoskeleton involves deposition of calcium carbonate by the polyps from calcium ions they accumulate from seawater
Catching a prey The polyp's tentacles trap prey using stinging cells called nematocytes These are cells modified to capture and immobilize prey such as plankton, by injecting poisons, firing very rapidly in response to contact The toxins injected by nematocysts immobilize or kill prey Then it will be drawn into the polyp's stomach by the tentacles
Nematocyst discharge: (1) A dormant nematocyst (2) discharges its stinging apparatus in response to nearby prey 3), leaving a barbed stinging filament (4) with which to draw in the prey. Catching a prey Nematocyst Filament
Reproduction
Three methods Reproduction Broadcast Spawning corals release gametes - eggs and sperm - into the water to spread colonies over large distances - Brooders They will release the sperm into the water but will house the eggs - Asexual - Fragmantation : Forms two polyps as large as the original - Budding : new polyp growing from an adult
Coral Mating During the mating season coral polyp release eggs and sperm into the water and when an egg and a sperm meet they form a larva known as a planula
Coral Mating coral Egg
Asexual Reproduction Gemmation (small central calicle) Division (large double calicle).
World-Wide Distribution of Reefs
World wide distribution of Reefs Coral reefs are estimated to cover 284,300 square kilometers with the Indo-Pacific region accounting for 91.9 percent of the total Southeast Asia accounts for 32.3 percent of that figure Pacific including Australia accounts for 40.8 percent Atlantic and Caribbean coral reefs only account for 7.6 percent of the world total
Coral reef restricted areas Coral reefs are either restricted or absent from along the west coast of the Americas, as well as the west coast of Africa due to upwelling and strong cold coastal currents that reduce water temperatures in these areas Corals are also restricted from off the coastline of South Asia from Pakistan to Bangladesh They are also restricted along the coast around north-eastern South America and Bangladesh due to the release of vast quantities of freshwater from the Amazon and Ganga Rivers respectively
Types of Reefs Coral Reefs are classified into three main types Fringing Reef 2. Barrier Reef 3. Atoll
Fringing Reef Lagoon Relatively young They develop along the coasts in shallow waters The corals grow upwards to sea level or just below and outwards towards the open ocean Fringing reefs are generally narrow platforms a short distance from shore and don't contain a substantial lagoon
Barrier Reef A coral reef growing parallel to the coastline and separated from it by a lagoon is called a barrier reef The lagoon may develop between the fringing reef and the land Barrier reefs can also originate offshore if the depth of the seabed out there is shallow enough to allow corals to grow
The Great Barrier Reef World s s largest coral reef system Composed of roughly 3,000 individual reefs and 900 islands, that stretch for 2,600 kilometres (1,616 mi) The reef is located in the coal sea, off the coast of Queensland in north-east Australia The Great Barrier Reef can be seen from outer space and is sometimes referred to as the single largest organism in the world
Atoll Atolls are rings of reef, often encircling an island having a shallow, sandy, sheltered lagoon in the middle Atolls grow on top of the submarine mountains which are remains of volcanoes Atolls were fringing reefs grown surrounding these volcanoes. When the volcanoes submerge into the water what remains is a ring of grown reefs called as Atolls.
Environmental Threats Runoff and coastal development - Industrialization in the coastal areas causes the water to get polluted with chemicals Shipping and oil Ship routes through the reef formations causes damage due to human error Wastes released from ships are a great threat eg Toxic paints, Wastes released from the engines Spilling of oil from the oil wells in the sea
Environmental Threats Over fishing Over fishing disrupts the food chains vital for the life cycle of corals causing un sustainability in their life cycle. -Fishing using dynamites causes the reefs to get damaged
Environmental Threats Crown-of of-thorns starfish A fish that eats corals by injecting digestive enzymes on the corals an sucks the liquefied tissue
Environmental Threats Coral Bleaching coral loosing its color Global warming and coral bleaching Due to global warming sea temperatures grow causing the corals to release the Photosynthesizing Zooxanthellae. Zooxanthellae gives the color to the corals once they are released the calcium carbonate skeletons appear as white which is called as coral bleaching. If the water did not cool within about a month period the coral will die
IMPORTANCE OF CORALS They provide protection and shelter for many different species of fish. Without coral reefs, these fish are left homeless with nowhere to live and no where to have their babies. These fishes are food for many millions of people. People use to sell the beautiful fishes caught in the coral reefs as pets And coral are very important in controlling how much carbon dioxide is in the ocean water, by changing the carbon dioxide into Calcium Carbonate Coral reefs are very important because they protect coasts from strong currents and waves by slowing down the water before it gets to the shore
Corals Should be prevented Cradle to Myriads of Species Millennia to Create Moments to Destroy " --Jim Morris