The development of an oil shale industry appears to be supported by local, state and federal governments. Millions of dollars of infrastructure support and payroll tax concessions is provided by the Queensland government....'and an excise exemption worth $200 million over five years from the federal government on the naptha [shale oil] extracted and sold to refineries.' (Bulletin, 23 March 1999)

The Crown-of-thorn starfish

Since the mid-1960s, immense numbers of crown-of-thorn starfish have been feeding on the living coral of the reef. This in turn has lead to the destruction of large areas of what would have become new reef and without continuous and regular new growth, the Great Barrier Reef faces the danger of gradually disappearing as the old reef wears away.

Although large outbreaks of these starfish are believed to occur in natural cycles, human activity in and around the Great Barrier Reef can worsen the effects. Reduction of water quality increases and an increase in the nutrient availability associated with agriculture can cause the crown-of-thorns starfish larvae to thrive.

Over fishing of its natural predators, such as the Giant Triton, is also considered to contribute to an increase in the number of crown-of-thorns starfish which often leads to outbreaks.

Anchoring

Anchoring by boats in coral reef areas is a cause of some major coral damage in heavily used areas. Anchors dropped in areas with more fragile coral species inevitably breaking at least some corals. While broken fragments of some species are capable of regenerating, recovery from a single anchoring event could take from one to ten years and repeated anchoring in the same area can result in persistent decrease in coral cover and species diversity that is ecologically unsustainable.

Diving and snorkeling

Divers, snorkellers and reef walkers can damage or break corals through physical contact. High levels of damage occur around high-use areas, especially around mooring areas and other tourist facilities.

Coral bleaching

Reefs are a unique partnership between the coral which is an animal and microscopic plant cells called zooxanthellae which give the reef it colours. The plants feed off the animal waste and in turn create food for the coral through photosynthesis. Both animal and plant are mutually dependent on each other for survival, a relationship known as symbiosis.

When coral is experiencing stress they expel their photosynthesizing zooxanthellae and turn colourless, revealing their white calcium carbonate skeletons, this is referred to as coral bleaching.

Stresses include changes in water salinity from heavy freshwater runoff, rises in water temperature from high levels of solar radiation during very calm periods or extremely low tides and pollution.

In some parts of the world bleaching may be a natural seasonal phenomena and the corals recover. But if the stress and disruption to the partnership is extreme or prolonged and the plant cells do not return to the coral then without a food supply the coral and plant cells eventually die.

Coral bleaching has been increasing dramatically around the world since the early 1980s. In 1998 coral bleaching was the worst in recorded history affecting thousands of square kilometres and some areas are unlikely to ever recover. The bleaching coincided with the peak of the 5 to 8 year cycle of El Nino and the change to a strong La Nina effect. In the past there have been natural shifts in the different types of corals living on a reef, which are part of the normal pattern of variability. If it is a rare event then the coral will recover and the long-term consequences will be relatively minor. If, however, these bleaching events are repeated as a result of natural and human causes the consequences would be devastating for the world's coral reefs.

Global warming.

It is predicted by most scientists that if the world maintains its burning of fossil fuels at current levels then we can expect the average temperature of the oceans to increase between 3 and 7 degrees Centigrade over the next fifty years. This is due to the build up of carbon dioxide in the atmosphere and the creation of a so-called Greenhouse effect. For more detail see 'Greenhouse' in our list of subjects. Global warming will almost certainly cause a rapid deterioration of the world's coral reefs and it has been suggested that the 1998 peak in coral bleaching was an early warning of what is to come due to a combination of El Nino and the Greenhouse effect.

  Return to Coral Reefs Introduction

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Coral Reefs Causes of the deterioration of the Great Barrier Reef Land based pollution. Run off from sugar cane production and other types of agriculture, the grazing of cattle and fertiliser used on gardens are the cause of rising levels of nutrients which have killed off much of the inshore hard corals of the reef. Increased quantities of nitrogen and phosphorus from run-off encourage algal growth, which in turn places added stress on the reef, reducing its strength and growth. It is estimated that 10,000 tonnes of phosphorus and 100,000 tonnes of nitrogen each year are washed from the land into the waters of the Great Barrier Reef. Coastal development. Heavy industry near the coastline is a continuing source of pollution. A combination of treated and untreated sewage is placing a lot of stress on the reef. Estuaries and wetlands that are vital to the reef's ecosystem are also being cleared to make way for tourism and residential development. Over fishing Unsustainable and destructive fishing continues throughout most of the Great Barrier Reef and oil spills from all types of ships and boats are an additional threat to the reefs viability. Prawn trawling is one example of destructive fishing because it entails dragging very large, heavy net gear weighing thousands of kilograms across the seabed. It is widespread with 90 per cent of lagoons and 50 per cent of the inter-reef areas being made available to trawling. Currently 840 boats are licensed to trawl. Studies show that each trawl removes about 5 to 20 per cent of the plants and animals from the seabed. If an area of seabed had been trawled 13 times, 70 to 90 per cent of the areas marine life would have been removed. This type of destructive fishing threatens the survival of these poorly studied sea floor communities that may have a vital part to play in the overall ecology of the Great Barrier Reef. Ballast water It has been estimated that 120 million tonnes of ballast is dumped in Australian coastal waters by foreign ships each year. Marine pests are brought in with the discharged ballast and they disrupt local ecosystems. Over 80 exotic species have been identified in Australian waters. The International Maritime Organisation should implement a management program to control and enforce ballast dumping in coastal water. Oil shale mining Along the coast of Queensland oil shale is mined for the production of oil. This is oil with a greenhouse intensity 60% higher than conventional oil, even greater than brown coal, the dirtiest conventional fossil fuel. The centre for its extraction and processing is the Stuart Oil Shale Plant, north of Gladstone, Queensland. Oil shale mining poses a threat to the survival of the reef. The cumulative effect of this and other industrial development along the coastline will prove devastating for the reef. The immediate environmental impacts of oil shale mining are: The threat of pollution to the local wetlands and estuarine ecosystems by acid leachate which is formed when certain rock types found in association with shale are exposed to air and water. Air pollution with the potential for 'acid' rain over local fruit growing and important coastal areas. Land clearance in world heritage areas to accommodate the mine. This will add sediment and heavy metal pollution to the narrows - a wetland area of national importance and part of the Great Barrier Reef World Heritage Area - killing seagrass beds and critical dugong and fish habitats. Land clearance also adds to the loss of habitats in general. The development of an oil shale industry appears to be supported by local, state and federal governments. Millions of dollars of infrastructure support and payroll tax concessions is provided by the Queensland government....'and an excise exemption worth $200 million over five years from the federal government on the naptha [shale oil] extracted and sold to refineries.' (Bulletin, 23 March 1999) The Crown-of-thorn starfish Since the mid-1960s, immense numbers of crown-of-thorn starfish have been feeding on the living coral of the reef. This in turn has lead to the destruction of large areas of what would have become new reef and without continuous and regular new growth, the Great Barrier Reef faces the danger of gradually disappearing as the old reef wears away. Although large outbreaks of these starfish are believed to occur in natural cycles, human activity in and around the Great Barrier Reef can worsen the effects. Reduction of water quality increases and an increase in the nutrient availability associated with agriculture can cause the crown-of-thorns starfish larvae to thrive. Over fishing of its natural predators, such as the Giant Triton, is also considered to contribute to an increase in the number of crown-of-thorns starfish which often leads to outbreaks. Anchoring Anchoring by boats in coral reef areas is a cause of some major coral damage in heavily used areas. Anchors dropped in areas with more fragile coral species inevitably breaking at least some corals. While broken fragments of some species are capable of regenerating, recovery from a single anchoring event could take from one to ten years and repeated anchoring in the same area can result in persistent decrease in coral cover and species diversity that is ecologically unsustainable. Diving and snorkeling Divers, snorkellers and reef walkers can damage or break corals through physical contact. High levels of damage occur around high-use areas, especially around mooring areas and other tourist facilities. Coral bleaching Reefs are a unique partnership between the coral which is an animal and microscopic plant cells called zooxanthellae which give the reef it colours. The plants feed off the animal waste and in turn create food for the coral through photosynthesis. Both animal and plant are mutually dependent on each other for survival, a relationship known as symbiosis. When coral is experiencing stress they expel their photosynthesizing zooxanthellae and turn colourless, revealing their white calcium carbonate skeletons, this is referred to as coral bleaching. Stresses include changes in water salinity from heavy freshwater runoff, rises in water temperature from high levels of solar radiation during very calm periods or extremely low tides and pollution. In some parts of the world bleaching may be a natural seasonal phenomena and the corals recover. But if the stress and disruption to the partnership is extreme or prolonged and the plant cells do not return to the coral then without a food supply the coral and plant cells eventually die. Coral bleaching has been increasing dramatically around the world since the early 1980s. In 1998 coral bleaching was the worst in recorded history affecting thousands of square kilometres and some areas are unlikely to ever recover. The bleaching coincided with the peak of the 5 to 8 year cycle of El Nino and the change to a strong La Nina effect. In the past there have been natural shifts in the different types of corals living on a reef, which are part of the normal pattern of variability. If it is a rare event then the coral will recover and the long-term consequences will be relatively minor. If, however, these bleaching events are repeated as a result of natural and human causes the consequences would be devastating for the world's coral reefs. Global warming. It is predicted by most scientists that if the world maintains its burning of fossil fuels at current levels then we can expect the average temperature of the oceans to increase between 3 and 7 degrees Centigrade over the next fifty years. This is due to the build up of carbon dioxide in the atmosphere and the creation of a so-called Greenhouse effect. For more detail see 'Greenhouse' in our list of subjects. Global warming will almost certainly cause a rapid deterioration of the world's coral reefs and it has been suggested that the 1998 peak in coral bleaching was an early warning of what is to come due to a combination of El Nino and the Greenhouse effect.   Return to Coral Reefs Introduction