PhD student Alison Jones surveys her tagged corals which she has been monitoring for the last years as part of her studies at Miall Island in the Keppel Island group. 100% of corals died on the reef flat died during a freakishly timed rainstorm which coincided with an extreme spring low tide. Photo: Dr R. Berkelmans, Australian Institute of Marine Science.

27 November 2006

The combination of a moderate rainstorm and an extremely low tide has caused mass mortality in shallow water corals around the Keppel Islands.

Corals living on the reef flat were high and dry at around 2 am on November 4thwhen a patchy rainstorm bathed the exposed reef with 17-0 mm of fresh water.

Scientists from the Australian Institute of Marine Science (AIMS) surveyed numerous reefs around the islands and found that the bulk of the damage was localised to areas where shallow reefs fell within the path of the storm.

In the impact areas, 100% of the shallow water corals have died. Deeper water corals and corals that were not in the direct path of the storm survived. While this event represents a major impact to the reefs in the area, it is not an ecological disaster. The corals are likely to recover if there are no other disturbances. The remaining corals will be critical to the reef's natural recovery process.

AIMS coral expert Dr Ray Berkelmans said that recovery of the reefs is likely to be slow.

"It will be 4-5 years before we will start to see any visual improvements in the affected region. In 7-10 years we should start to observe some good coral cover but it will take 15 years for the reefs to recover to their former condition assuming that there are no other disturbances."

 

Dr Berkelmans fears, however, that the Great Barrier Reef is likely to experience additional disturbances and more coral bleaching next summer as Australia is currently in an El Niño cycle which means unpredictable weather and often strong heat waves.

Dr Berkelmans and his team also monitored the impact of the coral bleaching event that impacted the region earlier this year. The 2006 bleaching event was the worst bleaching event on record for the Keppel Islands.

"While the reefs in the Keppels have amongst the highest coral cover anywhere on the Great Barrier Reef, this year's bleaching event caused just under half of the region's corals to die off. Now we are seeing patches of reef where all the coral is dead which is quite unusual for this area. Fortunately though, many of the seaward reefs are still in good condition."

Dr Berkelmans' previous research on coral bleaching has shown that corals around the Keppel Islands are generally quite resilient to bleaching events due to their unique ability to adapt to changing environments.

"While Keppel corals are typically more resilient to temperature changes than corals in other regions, no corals can tolerate prolonged exposure to freshwater so this sort of event is both unpredictable and unmanageable. These sorts of events demonstrate the importance of minimising human induced stress on the reef to ensure that they are as healthy as possible when disaster strikes."

This is not the first time reefs around the Keppel Islands have been exposed to freshwater. A major flooding of the Fitzroy River in 11 doused Keppel Bay and its fringing reefs in 18 million megalitres of freshwater causing mass destruction of corals within 4m of the surface.

"The positive side of all this is that we know that these reefs have recovered from a similar event in the past to become some of the most spectacular reefs on the GBR."

Media contacts:

Dr Ray Berkelmans , AIMS Research Scientist
Telephone : 07 4753 4268
Email : r.berkelmans@aims.gov.au

 

Wendy Eller y, AIMS Media Liaison
Telephone : 07 4753 440 Mobile :0418 729 265
Email : w.ellery@aims.gov.au