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GREAT BARRlER REEF - Saint Ignatius' Moodle Community

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The fragile Great Barrier Reef ecosystem is under stress and its health is declining.<br />

Reduced water quality<br />

Healthy coral reef ecosystems need clean saltwater.<br />

Catchment run-off from nearby farms is introducing soil<br />

sediment, fertiliser and pesticide poisons into the Reef’s<br />

waters. The water is becoming cloudier, which prevents<br />

sunlight from reaching the corals. Climate change is<br />

increasing water temperature, making it more acidic, and<br />

raising the sea level. These factors are working together<br />

to kill marine animal and plant species. It is also making<br />

them more vulnerable to disease.<br />

For much of the Great<br />

Barrier Reef, the chemical<br />

environment has deteriorated<br />

significantly, especially close<br />

to developed areas. This trend<br />

is expected to continue.<br />

Great Barrier Reef Marine<br />

Park Authority, Outlook Report,<br />

2009<br />

Threatened species<br />

So few of some species are left in parts of the Great Barrier Reef that they<br />

are in danger of becoming extinct in the region. Examples include triton<br />

shells, barramundi, some sharks, turtles and<br />

dugongs. Numbers of plant-eating dugongs<br />

are so low in the southern Reef region that the<br />

plant populations have been affected. The food<br />

web and whole Reef ecosystem have changed,<br />

perhaps forever.<br />

Threatened dugongs<br />

Dugongs were commercially hunted in the<br />

Great Barrier Reef until 1976. More recently,<br />

deaths have been caused by accidental<br />

capture in fishing nets, illegal hunting,<br />

pollution, disease and injury by boats.<br />

South of Cooktown, only 3 per cent remain<br />

compared to 40 years ago.<br />

The effect of pollution on the Great Barrier Reef’s water<br />

Aspect of water<br />

quality<br />

Change observed<br />

Effect<br />

Sediment Increased four to five times since European settlement Clouds water, killing corals<br />

Nitrogen<br />

Phosphorous<br />

pH<br />

Increased two to five times since European settlement<br />

Increased four to ten times since European settlement<br />

Decreased 0.1 units (becoming more acidic) since<br />

European settlement<br />

Promotes seaweed growth,<br />

smothering corals<br />

Promotes seaweed growth,<br />

smothering corals<br />

Decreases building of coral<br />

skeletons<br />

Sea temperature Has risen for long periods twice since 2002 Coral bleaching<br />

Sea level Increased 3 milllimetres per year since 1991<br />

Ultimately blocks light, killing<br />

corals<br />

18<br />

The number of dugongs in the southern Great Barrier Reef remains low, despite<br />

protection areas being set up and Indigenous Australians agreeing to decrease<br />

traditional hunting.<br />

Macmillan Digital Library: What’s the Issue? Set 2 © Michelle Atkins, Julie Murphy, Greg Reid, Geoff Thompson, Ashten Warfe/Macmillan Publishers Australia 2011 ISBN 978 1 4202 9209 1 Macmillan Digital Library: What’s the Issue? Set 2 © Michelle Atkins, Julie Murphy, Greg Reid, Geoff Thompson, Ashten Warfe/Macmillan Publishers Australia 2011 ISBN 978 1 4202 9209 1<br />

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