Luke Simpkins (Cowan, Liberal Party) Share this | Link to this | Hansard source

asked the Minister for Sustainability, Environment, Water, Population and Communities, in writing, on 21 February 2011:

(1) In each calendar year since 1997, how many coral bleaching incidents have occurred on (a) the Great Barrier Reef, and (b) Ningaloo Reef.

(2) On what (a) date, and (b) part of the reef, did each incident occur; and what was the size of each affected area.

Mr Tony Burke (Watson, Australian Labor Party, Minister for Sustainability, Environment, Water, Population and Communities) Share this | Link to this | Hansard source

The answer to the honourable member's question is as follows:

(1) Widespread coral bleaching incidents are typically caused by extreme sea temperatures; however localised bleaching can also be caused by exposure to freshwater (rain and flood waters) and pollutants.

(a)

Great Barrier Reef

I am advised that three significant coral bleaching incidents have occurred within the Great Barrier Reef Marine Park since 1997 as a result of prolonged elevated sea temperatures. Two widespread incidents occurred in the summers of 1997/8 and 2001/2 and a localised but severe incident occurred in the summer of 2005/6. Some localised patchy coral bleaching has also been reported at individual reefs across the Great Barrier Reef each summer since 1997.

2010-2011 Floods:

Bleaching has been reported on some fringing reefs in the Keppel Island Group as a result of the recent flooding.

(b)

Ningaloo Reef

I am advised that the coral reef communities of Ningaloo Marine Park that are susceptible to coral bleaching occur in State waters which are managed by the Western Australian Department of Environment and Conservation. Water depths within the Commonwealth waters of the Park range from about 30m to greater than 500m.

Since 1997, there have been three bleaching episodes recorded on Ningaloo Reef. A cold water bleaching event occurred in 2006; bleaching related to anoxic water after coral spawning occurred in 2008; and the first recorded warm water bleaching event occurred in February 2011.

(2) Widespread coral bleaching incidents typically develop over the course of several months as a result of prolonged elevated sea temperatures, but can also result from other factors affecting water quality.

(a)

Great Barrier Reef

I am advised that in the summers of 1997/98 (January-March) and 2001/2 (January – April) 50 per cent of the 2900 reefs within the Great Barrier Reef Marine Park were affected by widespread coral bleaching incidents. In each case five per cent of reefs suffered lasting damage. In 2006 (January – February) a severe localised bleaching event focused at the southern end of the Marine Park caused 40 per cent mortality of reefs in the Keppel Bay area.

2010-2011 Floods:

The 2010-2011 Queensland summer (December to March) was the sixth wettest since records began and heavy flooding has persisted for several months throughout most of south-eastern Queensland. These floods have caused high turbidity and increases in sedimentation and chlorophyll levels in inshore areas exposed to the flood plumes. Corals stressed by decreased salinity and high turbidity can bleach, although salinity-induced bleaching is usually localised and confined to shallower areas where the largest salinity decrease occurs.

Ningaloo Reef

I am advised that the cold water bleaching occurred during winter (July) 2006. The bleaching event related to anoxic water after coral spawning occurred in late March 2008. The only warm water bleaching event began in February 2011.

(b)

Great Barrier Reef

I am advised the1997/8 incident primarily affected the inshore and mid-shelf reefs between Cooktown and Townsville and the inshore reefs between Ayr and Gladstone. In 2001/2 a larger proportion of mid-shelf reefs were affected by bleaching between Port Douglas and Rockhampton.

2010-2011 Floods:

Bleaching has been reported on some fringing reefs in the Keppel Island Group as a result of this current flooding, however, as rainfall has continued to occur in this area, it is too early to assess the full extent of the bleaching. Localised coral bleaching has also been observed on the reef flat at Heron Island although reports from the research station indicate this is a result of intense rainfall during very low tides.

Ningaloo Reef

I am advised that in July 2006 bleaching affected the entire length of Ningaloo Reef. Good coral recovery was observed at all sites with very minor mortality. The anoxic bleaching event in 2008 occurred in Bills Bay (Coral Bay) and coincided with fish kills. Between 20-40 per cent of coral in a 1.2km2 area was affected and did not recover. Bleaching in February 2011 was observed along the entire length of Ningaloo Reef. Areas in the Exmouth Gulf (100 per cent of coral affected), the Muiron Islands (50-80 per cent coral affected), and Coral Bay (40-60 per cent of coral affected) had higher percentage bleaching than other areas along the reef system. Detailed assessments will be finalised in the coming months and will provide a basis for assessing recovery.