The AIMS Long Term Monitoring Program (LTMP) has been surveying the health of 47 reefs in the Great Barrier Reef annually since 1993. This represents the longest continuous temporal record of change in reef communities over such a large scale. Please, have a look at several reports two days ago:
http://www.reuters.com/article/2012/10/01/us-australia-reef-idUSBRE89018K20121001
and watch also the short interview with the Federal Environment Minister Tony Burke from Australia.