Survey finds Great Barrier Reef coral losing strength

0410lizard_island_locator-300x0The skeleton hand of ocean acidification has been found at work near one of Australia’s most exotic tropical destinations, Lizard Island on the Great Barrier Reef.

Scientists surveying a reef flat just south of the resort island, off Cooktown, have measured a near 40 per cent decline in deposition of the vital building block for healthy coral, calcium carbonate.

The fall, detected by a team from Israel’s Hebrew University, underscores the need for rapid action to arrest ocean acidification caused by climate change, Australian marine scientist Ove Hoegh-Guldberg said on Friday.

Coral reefs of the Great Barrier Reef such as those around Lizard Island support rich marine life that underpins an estimated $5.6 billion tourism industry, according to a Deloitte Access Economics study. But even slightly more acidic seawater can reduce the ability of the corals to grow the strong calcium carbonate shells needed to withstand the rigours of life in the ocean.

A landmark Australian Institute of Marine Science study in 2009 tracked an 11.2 per cent decline over 15 years in calcification of massive porites-type corals throughout the Great Barrier Reef system – unprecedented in at least the past 400 years.

At the Lizard Island reef, acidification effects were detected across the whole coral community surveyed. The results were published in a study this week that compared calcification rates in 2008-09 with an original survey in 1975-76.

The Hebrew University researchers found that although the extent of coral cover was about the same as when it was first examined, calcification rates had fallen by between 27 and 49 per cent, leaving the corals less dense and more fragile.

These lower rates are consistent with predictions that take into account the increase in carbon dioxide uptake in the ocean over the same 33-year time span.

“The results of this study show a dramatic decrease in the calcification of the reef, and that it was likely caused by ocean acidification,” Jonathan Erez, of Hebrew University, said.

“When the rate of calcification becomes lower than the rate of dissolution and erosion, the entire coral ecosystem could collapse and eventually be reduced to piles of rubble,”

Professor Hoegh-Guldberg, of the University of Queensland, said the Lizard Island study was a valuable field measurement that helped to validate work on the effects of ocean acidification.

“These measurements are finding that the expected decline has happened,” Professor Hoegh-Guldberg said.

“It shows the threat of climate change to some of the most important ecosystems on the planet, the coral reefs. It should spur our policymakers to more rapidly decarbonise society.”

The Great Barrier Reef Marine Park Authority’s 2014 Outlook Report assessed ocean acidification as a very high risk to the reef.

However, the risk is not dealt with in the federal and Queensland governments’ draft Reef 2050 Long-Term Sustainability plan, which refers to unspecified action to “maximise the reef’s resilience to the current and future effects of climate change”.

The Australian Marine Conservation Society’s Lissa Schindler said: “The Reef 2050 plan doesn’t really do anything to engage on climate change. It needs to think bigger.”

Meanwhile, the Lizard Island resort’s website says it will remain closed until at least early 2015, while it is rebuilt after being extensively damaged by tropical cyclone Ita on April 11. Possibly fewer, but more intense, cyclones are also predicted under climate change, according to the Bureau of Meteorology.

Andrew Darby, The Sydney Morning Herald, 4 October 2014. Article.


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