Coral bleaching has been reported on Ningaloo – a reef system that has not experienced widespread bleaching to date. Coral bleaching likelihood is largely determined by sea temperatures, and during the 2010/2011 summer, sea surface temperatures across Ningaloo were anomalously warm.
Coral bleaching events are usually caused by long periods (usually 4 to 8 weeks) of warmer than average summer sea surface temperatures (SSTs), and SST estimates from the National Oceanographic and Atmospheric Administration (NOAA) Coral Reef Watch Program show that 2010/2011 summer SSTs around Ningaloo have been about 1°C to 3°C warmer than the long-term averages for the region. As a result, Ningaloo was on Bleaching Watch for much of the summer and reached 4 Degree Heating Weeks (DHW)1 in mid-January 2011 (Figure 1A). In situ temperature loggers (~ 6 m depth) at Bundegi in the Exmouth Gulf and 14-Mile Beach on Ningaloo (Figure 1B) confirmed that actual water temperatures had been above seasonal averages since mid October 2010.
Figure 2. Coral bleaching at Coral Bay (10 February 2011). A. Acropora and Favia; B. Seriatopora;