Recurrent bleaching of corals at Magnetic Island (Australia) relative to air and seawater temperature

Abstract

Coral bleaching events have occurred on the fringing reefs of Magnetic Island (Great Barrier Reef region), Australia, during the summers of 1979/80, 1981/82, 1986/87, 1991/92 and 1993/94. Continuous in situ water temperature recordings since 1991 suggest a close correlation between bleaching of corals and periods of average daily seawater temperatures approaching 32°C. Each of the bleaching events has occurred during periods of unusually high air temperatures, suggesting that 'heat waves' cause a warming of the inshore waters and are a contributory factor in the recurrent bleaching of corals at Magnetic Island. There has been a significant increase in annual summer and winter air temperatures in the Magnetic Island area since the middle of the present century. Significant warming trends have also been observed in the nearby state of Queensland and in Eastern Australia over the same period. Air temperatures similar to those present during the 5 bleaching events which occurred at Magnetic Island have not otherwise been experienced in this area since the 1930s.