The effect of coral bleaching on the cellular concentration ofdimethylsulphoniopropionate in reef corals

Measurements of DMSP production from Acropora intermedia collected from Heron Island, in the southern Great Barrier Reef (GBR) from 2001 to 2003, show a distinct seasonal cycle of increased production in summer, and lower production in winter, despite severe coral bleaching in 2002. Increasing seawater temperatures by + 2 °C in summer and winter increased DMSP production from A. intermedia by approximately 45%. Compared with winter 2001 and summer 2002, marked increases in cellular DMSP occurred in A. intermedia in the winter of 2002 and summer 2003, five to six months after coral bleaching, and seemed to be related to high seawater temperatures and high rainfall. In contrast to these results cellular Chl a concentrations in A. intermedia decreased from 2001 to 2002 and then increased in summer 2003 as the coral slowly recovered. A parallel study conducted on Pocillopera damicornis from a fringing reef off Magnetic Island in the central GBR, highlighted marked variation in cellular concentrations of Chl a, DMSP, and algal symbionts, in colonies that were collected five months after a severe bleaching event. The increases in cellular DMSP at both low and high symbiont concentrations, and the highly significant correlation between cellular DMSP and Chl a, could reflect an adaptive response to enhanced levels of reduced oxygen species produced during the bleaching event, and may have aided the coral's recovery. The increases in cellular DMSP could also be explained by a change in the symbiont community. Comparison with measurements made mainly on Acropora coral from different locations in the GBR over different years, suggests that changes in the cellular or tissue concentration of DMSP are a sensitive indicator of coral stress.