The Joseph Bonaparte Gulf (JBG) is an offshore area in northern Australia, with active petroleum exploration and infrastructure development. The Van Diemen Rise, an area of raised banks and channels in the northeastern region of the JBG, has been proposed for protection as part of the Oceanic Shoals Commonwealth Marine Reserve. However, baseline information for much of this area is lacking, including spatial and environmental patterns of biological communities. This study uses still imagery of the sea floor in four study areas across the Van Diemen Rise, collected during two seabed mapping surveys conducted by Geoscience Australia and the Australian Institute of Marine Science, in 2009 and 2010. Based on these analyses benthic communities are characterised, and important species and morphological groups are compared with a number of abiotic variables. In so doing, a preliminary assessment is given as to which abiotic variables make the most appropriate surrogates for characterising benthic communities in the region. A number of variables are found to correlate significantly and strongly with some of the biological groups determined in this study. Pheophytin, Si/Al and mud content correlate with the large habitat forming species Mopsella sp., Ianthella sp. and Xestospongia sp. respectively. Backscatter signals from multibeam sonar surveys correlate very strongly with depth and also to some degree with a number of the functional growth forms of sponges. Based on the positive results of this preliminary data investigation, it is recommended that non-linear modelling and robust multivariate analyses be applied to the data set to investigate more complex relationship. This study provides baseline information on the ecology and morphology of key habitat-forming organisms in the northeastern Joseph Bonaparte Gulf which will be facilitate marine monitoring programs for reserve management and environmental impact assessments for industry activity.
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