Great Barrier Reef damaged by severe tropical cyclone Larry


10 November 2006

Tropical cyclone Larry, which severely devastated an 80 km stretch along North Queensland's coast, also had an impact on the coral reefs in its path.

Scientists at the Australian Institute of Marine Science (AIMS) have returned from completing comprehensive surveys of 05 sites on 20 coral reefs within the impact zone of cyclone Larry. They found that damage caused by the category five cyclone was extremely patchy and was the greatest just south of Larry's path.

This reef was directly in the path, but showed surprisingly little damage.
Taken on the front of Feather Reef. This reef was directly in the path, but showed surprisingly little damage. Photo shows the most fragile coral growth forms still present.
Photo: AIMS LTMT.

Newly created rubble bank at bottom of slope on NE corner of Taylor Reef, a midshelf reef.
Newly created rubble bank at bottom of slope on NE corner of Taylor Reef, a midshelf reef.
Photo: AIMS LTMT.

Parts of the offshore Yamacutta Reef were badly damaged.
Parts of the offshore Yamacutta Reef were badly damaged. However the damage was restricted to a few thousand square meters on the windward side.
Photo: Katharina Fabricius.

n contrast, the offshore Gilbey Reef nearer to Innisfail had beautiful patches of coral left even after the cyclone went over it.
In contrast, the offshore Gilbey Reef nearer to Innisfail had beautiful patches of coral left even after the cyclone went over it.
Photo: Katharina Fabricius.

Dr Hugh Sweatman, Senior Research Scientist at AIMS, has been involved in monitoring the Great Barrier Reef for the last ten years.

"Cyclone Larry caused severe damage to some inshore reefs which previously had high coral cover. The offshore reefs fared better but one of the contributing factors of this was their low coral cover caused by outbreaks of coral-eating crown-of-thorns starfish six to eight years ago.

"When Larry arrived, most of the reef's table and branching corals were still quite small and low in profile, and therefore not as susceptible to damage as larger colonies. Unfortunately, the reefs that suffered the worst impact were the ones that had the most to lose."

The AIMS team assessed the effects of the cyclone during a research expedition to the inshore and offshore reefs between Hinchinbrook and Cairns. The most commonly observed types of impact on corals were breakage of fragile table and branching colonies, and dislodgement of some small massive corals.

Expedition leader, Dr Katharina Fabricius said that while Larry's underwater impact on a few inshore reefs was severe, the cyclone's effect on offshore reefs was much less than she observed after cyclone Ingrid which decimated reefs in the far north in 2005.

"Larry crossed over the continental shelf within five hours which was too fast to generate extreme wave heights despite its record wind speeds. This, in combination with the low coral profile of the offshore reefs, may explain their lucky escape."

Dr Fabricius is concerned about the impacts climate change could have on the frequency of intense cyclones and on the extent of the damage they will cause to reefs in the future.

"Cyclones are normal events in the lives of coral reefs. However, the intensity of cyclones is predicted to increase due to global warming. It is imperative for us to understand how specific characteristics of cyclones, such as wind speed wind direction, wave height and duration of gale force winds, are related to reef damage."

The AIMS Long-term Monitoring Team will continue to report on the state and condition of these reefs as part of their ongoing program to monitor the Great Barrier Reef.

Media contacts:

Dr Katharina Fabricius , Principal Research Scientist
Telephone : 07 4753 4412 Mobile : 0428 713 845
Email : k.fabricius@aims.gov.au

Dr Hugh Sweatman ,Senior Research Scientist,
Telephone : 07 4753 4470; Mobile :0419 986 746
Email : h.sweatman@aims.gov.au

Dr Ian Poiner, AIMS CEO
Telephone : 07 4753 4490; Mobile :0419 702 652
Email : i.poiner@aims.gov.au

Wendy Ellery, AIMS Media Liaison
Telephone : 07 4753 4409; Mobile :0418 729 265
Email : w.ellery@aims.gov.au