GEO 5 UCLA CORAL REEFS FREE FROM SEDIMENT

In: Proceedings of 10th international coral reef symposium (in press) Oliver JK, Babcock RC, Harrison PL, Willis BL (1988) Geographic extent of mass coral spawning: clues to ultimate casual factors.In tropical seas, many types of coral animals and marine organisms such as coral polyps, calcareous algae, shell-forming creatures and lime-secreting plants live in large colonies. It is commonly known as the rainforest of oceans.Mangubhai S, Harrison PL (2005) Seasonal patterns of coral reproduction on equatorial reefs in Mombasa, Kenya. Evidence suggests that they started as simple, solitary organisms but, in response to changes in their environment, later evolved into the coral reefs we know today.Corals reefs are one of the most diverse habitats in the ocean. It lies between a well-sheltered, deepwater harbour, accessible to ships through a break in the coral reef, and a semicircle of mountains.: A remarkable natural gift, the Great Barrier Reef is blessed with the breathtaking beauty of the worlds largest coral reef.: You can scuba dive along the worlds second largest coral reef or swim in fresh water pools in submerged caverns, known as cenotes.Coral Reef History Corals are 500 million years old, and date back to the late Cambrian period, during the Paleozoic era (Fig.

The reef is 345,000 square kilometers in size along the east coast of Australia, which is about the size of California. Coral reefs have numerous species of many forms, colours, and shapes.It consists of over 2,900 reefs and around 940 islands. The landforms are popularly known as coral reefs.

As a rule, they thrive well only in the warmer tropical seas.There are two major types of corals: hard corals and soft corals, such as sea fans and gorgonians. Each polyp resides in a tiny cup of coral made of calcium carbonate and when a polyp dies the cup cement together to form the reef structure.There are also non-reef building species such as the 'precious corals' of the Pacific Ocean and the 'red coral' of the Mediterranean Sea which may survive in the colder and even the deeper waters. Among the numerous organism that forms the part of the coral habitat, the polyps are the abundant species.

The condition virtually limits the areal distribution of corals to the tropical, and sub-tropical zones. The surface water temperature of the ocean must not be less than 20 degrees Celsius. The reef-building corals survive best under the following conditions: The largest cold-water coral reef is the Rost Reef off Norway. According to the United Nations Environment Programme, there are more cold-water coral reefs worldwide than tropical reefs. While the majority of coral reefs are found in tropical and sub-tropical waters, there are also deep water corals in colder regions.

Zooxanthellae a type of algae live in a symbiotic relationship with coral polyps, algae produce food through photosynthesis and provide energy to polyps. The presence of warm current in the temperate ocean raises the temperature of ocean water in these places as a result, corals grow in these places in spite of the fact that the ambient temperature is below the threshold requirement. Since most of the cold current flows along the western border of continents, it explains the absence of corals from western coasts.

Geo 5 Ucla Coral Reefs Free From Sediment

The seaward side of the coral reefs is best developed because of the supply of oxygenated water by the constant flow of waves and tides.The three main types of coral reefs include, Corals, therefore, survive best in the moving ocean water well away from the silty coasts or muddy mouths of streams and rivers. The water should be salty and free from sediment. Below 180 feet depth, the sunlight is too faint for photosynthesis to take place. As a result, the corals are found at a depth not exceeding 180 feet.

Their outer edge grows rapidly due to the availability of oxygenated water and food supply by constant wave currents. Fringing reefs develop on the wave cut platforms along the continents and Islands. Sometimes they are separated by a shallow lagoon. They are the most common type of reef structure found in the ocean.

The best-known barrier reef is the Great Barrier Reef off the coast of Queensland, Australia. Such gaps are very useful for shipping and provide the only entrances for ships to enter or leave the lagoon. The barrier reefs have narrow gaps at several places to allow the water from the enclosed lagoon to return to the open ocean. Where it lies above the water level. The reef is partially submerged.

If the stress-causing bleaching is not too severe and if it decreases with time, the affected corals usually regain their symbiotic algae within several weeks or a few months. The concentration of photosynthetic pigments within the zooxanthellae fall.When the bleaching of corals occurs, they usually lose around 60-90 percent of their zooxanthellae, and each zooxanthella may lose around 50-80 percent of its photosynthetic pigments. the density of zooxanthellae residing inside the reefs declines. Some of the large atolls include Sudadiva in the Maldives, Bangaram atoll in Lakshadweep.Bleaching refers to the paling of coral colour. The encircling ring is usually broken in a few places to allow the free flow of water. Atolls: Atolls are similar to barrier reefs except that they are circular, enclosing a shallow lagoon without any land in the centre.

It is therefore difficult to unequivocally identify the causes for bleaching events. It can be induced by a variety of factors, alone or in combination. Causes of BleachingCoral reef bleaching is a reaction to the stress applied on the coral polyps. Photosynthesis pathways in zooxanthellae are impaired at temperatures above 30 degrees Celsius, and this could activate the dissociation of coral/algal symbiosis.

Inorganic nutrients: Rather than causing coral bleaching, an increase in ambient element nutrient concentrations (e.g. Generally, such bleaching events are rare and confined to relatively small, nearshore areas. Fresh Water Dilution: Rapid dilution of reef waters from storm-generated precipitation and runoff has been demonstrated to cause coral bleaching. It is possible but has not been demonstrated, that sediment loading could make zooxanthellae species more likely to bleach. Sedimentation: Relatively few instances of coral bleaching have been linked solely to sediment.

Epizootics: Pathogen-induced bleaching is different from other types of bleaching. Because high concentrations of xenobiotics are required to induce zooxanthellae loss, bleaching from such sources is usually extremely localized and transitory. Xenobiotics: Zooxanthellae loss occurs during exposure of coral to elevated concentrations of various chemical contaminants such as copper, herbicides, and oil. Although eutrophication is not directly involved in zooxanthellae loss, it could cause secondary adverse effects such as lowering of coral resistance and greater susceptibility to diseases.

Protozoans have been identified as some of the pathogens responsible for such conditions (translucent white tissues).