GBR - Benthic communities, juvenile corals and sources of coral mortality on the Great Barrier Reef (AIMS LTMP)

The purpose of this study is to detect and quantify spatial and temporal changes in benthic communities and juvenile coral assemblages of the Great Barrier Reef (GBR). Additionally, spatial and temporal variation in sources of coral mortality are monitored to assist with interpretation of changes in benthic assemblages. Between 1993 and 2005, benthic assemblages of 46 reefs were monitored annually along permanent transects within a standard habitat using underwater video/digital still photography. Percent cover of corals and other benthic categories are estimated using a point sampling technique, in which approximately 200 systematically dispersed points are sampled from 50 still frames taken along each transect.

The selected intensive survey reefs are distributed across three positions of the continental shelf and among six sectors each representing one band of latitude. These reefs continue to be surveyed in odd years only as part of the Long Term Monitoring Program (LTMP). The survey pattern changed in 2006 in response to the implementation of a new zoning plan for the GBR Marine Park in 2004. In order to assess the effects of re-zoning on the biodiversity of reefs, a different selection of reefs are surveyed in even years as part of the Representative Areas Program (RAP). Surveys are carried out for 28 pairs of reefs, one of which was re-zoned as a no-take area in 2004 while the other remains open to fishing. The RAP survey reef pairs are distributed among sectors along the GBR in a similar fashion to the original LTMP survey reefs.

SCUBA search surveys have been carried out at the LTMP intensive survey sites since their establishment and have also been incorporated in to the RAP sampling scheme. The SCUBA search technique involves recording the incidence of Crown Of Thorns Starfish (COTS), Drupella spp., bleaching and disease. Over the years the SCUBA search method has continually evolved to put greater emphasis on recording the incidence of disease and disease-like syndromes. For example, records of diseases causing death of coralline algae, such as Coralline Lethal Orange Disease (CLOD), and of overgrowth of healthy coral tissue by sponges and ascidians are relatively recent additions to the SCUBA search data.

Juvenile coral assemblages are an important component of coral community dynamics and reef recovery following disturbance. In 2007 juvenile coral surveys were added to both the LTMP and RAP sampling schemes. Juvenile corals up to 5cm in diameter are identified and recorded in situ along smaller-scale transects at the same permanently marked sites.