Coral reefs provide marine habitats for tube sponges, which in turn become marine habitats for fish (Wikimedia)
Corals—tiny animals related to jellyfish—would be over-run by seaweed. In the long term, interactions among reef organisms would lead to dominance by other groups, including sponges and soft corals known as gorgonians.Wikimedia

Live coral coverage on Australia's Great Barrier Reef could plummet to less than 10% if ocean warming continues according to current trends, finds a new study that explores the short- and long-term consequences of environmental changes to the reef.

The long-term consequences indicate that a moderate warming of 1-2 degrees Celsius can result in coral cover declining to less than 10%, the tipping point for reef growth.

In the short term, rising temperatures and pollution from human activities could see corals, tiny jellyfish-like animals, over-run by seaweed.

"The model indicated that warming of an additional 1-2 degrees Celsius would more than likely lead large declines in coral cover and overall changes to the community structure," says lead author Jennifer K Cooper, a graduate student in marine biology, at James Cook University.

"If our model is correct the Great Barrier Reef will begin to look very different as ocean temperatures increase."

Coral cover, a measure of the percentage of the seafloor covered by living coral, is now just 10-20% worldwide. The Great Barrier Reef has lost half of its coral cover in the last 27 years.

While the study matches recent findings that hold promise of reef recovery in the short-term, the longer term future prospects are bleak for the coral reefs.

Overfishing, coastal pollution and increased temperatures and ocean acidification from carbon emissions, as well as other human activities affect coral reef ecosystems.

The Great Barrier Reef, which stretches along most of the coastline of the state of Queensland and is about the size of Japan, contains the world's largest collection of coral reefs, with 400 types of coral, 1,500 species of fish and 4,000 types of molluscs.

The United Nations listed the reef as a World Heritage site in 1981, but is considering placing it on the List of World Heritage in Danger given the increased human disturbance.