Ecosystem impacted by extreme weather

The Extreme Weather Response Program focused on how floods and cyclones in the summer of 2010-11 affected coral reefs, seagrass, dugong and marine turtles, and islands in the Great Barrier Reef Marine Park.

Coral reefs

Flood plumes and cyclone Yasi combined to affect large areas of coral reef in the Great Barrier Reef Marine Park. Cyclone damage was both severe and widespread. Approximately six per cent of the reef area in the Marine Park suffered severe damage, with broken corals reported across an area exceeding 89,000 km2.

The most severe damage was confined to the area between Cairns and Townsville, sparing the key tourism areas off Cairns and Airlie Beach from major impacts. In contrast, the impacts of flood plumes were generally confined to shallow areas of inshore coral reefs near major rivers, such as those in the Keppel Bay region.

The report - Impacts of tropical cyclone Yasi on the Great Barrier Reef, presents the results of surveys conducted to assess the spatial extent and severity of physical damage caused by tropical cyclone Yasi to the coral reefs of the Great Barrier Reef Marine Park.

Coral trout

The Coral Reef Finfish Fishery is vulnerable to the effects of severe tropical cyclones as coral trout inhabit shallow coral reefs and these are most vulnerable to damage from cyclones.
Reports from commercial fishers indicate there has been a significant and sustained decrease in the catch rates of coral trout. However, early results from underwater surveys indicate this is due to fish 'going off the bite', rather than a decrease in fish abundance.

Seagrass

Seagrass can be vulnerable to the effects of reduced light during long periods of exposure to flood plumes. Scientists are still evaluating the impacts on seagrass meadows, however early indications suggest significant seagrass loss in at least some areas between Cairns and Hervey Bay.

Initial inspections of deep sites off Townsville using autonomous underwater vehicle found there has been damage to deepwater seagrass meadows in areas affected by cyclone Yasi.  Further work is continuing to better estimate the impacts on seagrass beds from extreme weather.

Dugong and turtle

Declines in seagrass from extreme weather events have serious implications for turtles and dugong as this is their main food source.

Impacts on populations can take many months or years to fully eventuate. However, the number of dead dugong and turtle reported along the Queensland coast in the first seven months after the extreme weather events exceeds any previous full year of records since reporting program began in 1996.

The Great Barrier Reef Marine Park Authority is working with Department of Environment and Heritage and research partners to monitor the effects on turtle and dugong populations in the wake of the extreme weather impacts.

Islands

Islands are very exposed to the destructive forces of cyclones, while major floods can substantially increase the risk of debris and pests arriving on islands.

Aerial photographic surveys of islands have revealed a number of cays have disappeared or altered shape and size following the recent cyclones. Several new rubble cays have appeared. Changes in islands and cays are being mapped and analysed using a geographic information system.

Cyclones can also affect bird species that depend on Great Barrier Reef islands for habitat. An assessment of impacts on seabirds will be done over summer, when the next breeding season occurs.