JOHN BREWER REEF
Intensive Surveys: Trends in cover of benthic organisms
Multiple disturbances have impacted the intensive survey sites at John Brewer Reef over the survey period. Hard coral cover reached a maximum of 31% in 1996. Small declines in hard coral cover were observed in 1998 and 1999 and were the result of storm damage (Cyclone Justin) and mortality following bleaching, respectively. Subsequently, substantial declines in hard coral cover occurred due to COTS feeding activity observed in 2002 and 2003. The highest density of feeding COTS recorded on scuba search occurred in 2003, at 1020 COTS/ha. COTS had reduced coral cover to less than 1% by 2004. By 2009 hard coral had increased to 4 and remained low in 2011 at 5%. It appeared that hard coral cover was not affected by Cyclone Yasi, due to the already low coral cover and small colony size. Changes in hard coral cover over the survey period were driven by growth and loss of tabulate and branching forms of the genus Acropora. The cover of soft corals was less than 5% since 1998 and in 2011 was 3%. Changes in algae cover have mirrored variation in hard coral cover, with 85% cover recorded in 2011. The algae community was comprised primarily of turf species. Individual Porites spp. and Montipora spp. colonies were bleached in 2011. White syndrome occurrence was rare and Drupella spp. were recorded at a density of 33/ha. No COTS have been recorded at intensive survey sites since 2004.