Each summer, we keep an eye on the Great Barrier Reef to see how it’s faring, as this period brings an increased risk to the Reef from coral bleaching, extreme weather and flooding. Stressful conditions can lead to coral disease outbreaks, and poor water quality may also lead to an increase in the abundance of coral eating crown-of-thorns starfish.

Environmental conditions

As at 5 February 2013, conditions on the Great Barrier Reef are neutral according to information from the Bureau of Meteorology:

• All indicators of El Niño-Southern Oscillation (ENSO), including trade winds and tropical cloud patterns, are currently within the neutral range.  This state is set to continue into autumn.
• Sea surface temperatures in the tropical Pacific Ocean were cooler than average in January, however climate model forecasts suggest that temperatures will rise in February and March. Since the beginning of February, sea surface temperatures within parts of the Great Barrier Reef Marine Park have risen to higher than average levels.
• A tropical low pressure system associated with ex-tropical cyclone Oswald crossed Cape York Peninsula on 21 January 2013 and moved down the Queensland coast, bringing strong to gale force winds, heavy rain, damaging waves and floods. 
• There is still a greater than 50 per cent chance that the Great Barrier Reef region will experience a below average number (less than four) of tropical cyclones this season.
• Following a period of below average rainfall in the Great Barrier Reef catchment during November and December 2012, rainfall levels from January 2013 increased to 50–400mm higher than average for the month.  Northern Queensland is now forecast to experience a wetter than normal period from February to April 2013.
• The heavy rainfall associated with ex-tropical cyclone Oswald resulted in flooding of many major river systems that flow into the Great Barrier Reef or bays in southern Queensland.  As at 29 January, minor to major flood warnings were current for all major river systems south of Mackay to the Queensland–New South Wales border. Flood plumes have been documented for several of these major river systems.

Reef health monitoring is ramped up over this time to keep an eye on the marine environment. Our table of observations and forecasts provides more detailed information.

Coral reef health reports

GBRMPA, the Queensland Parks and Wildlife Service (QPWS) and the Eye on the Reef monitoring network have conducted 1001 reef health and impact surveys across 132 reefs on the Great Barrier Reef since 1 July 2012.  

Detailed assessments of the impacts of ex-tropical cyclone Oswald on the sensitive ecosystems of the Great Barrier Reef Marine Park are pending. The high winds and heavy rainfall have potentially affected individual coral reefs and seagrass beds, particularly in southern areas. These effects include physical damage from waves, as well as the effects of low salinity, sediments and turbidity from the flood plumes.

Initial reports from the volunteer monitoring network indicate some coral damage on several reef sites in the northern Great Barrier Reef as a direct result of damaging winds and wave action. Assessments of reefs affected by the flood plumes will be undertaken once the plumes have cleared and visibility levels have improved. 

Before ex-tropical cyclone Oswald, reef-wide surveys showed:

• Some signs of coral stress, such as low level coral bleaching, disease and partial mortality.
  
• Increasing levels of coral predation, primarily from crown-of-thorns starfish. This is consistent with reports from the Australian Institute of Marine Science (AIMS) and the tourism industry.