Geophysical Variables as Predictors of Megabenthos Assemblages from the Northern Great Barrier Reef, Australia

The question as to whether geophysical data from habitats can be used to predict the occurrence of benthic biodiversi-ty is becoming more important with the increase in the use of Marine Protected Areas (MPAs) as tools for marine con-servation. To help answer this question and to better understand the relationship between sediment, geomorphology and benthos, a multibeam sonar survey was conducted over two areas in the northern Great Barrier Reef–Gulf of Papua region. Multivariate statistical analyses (cluster, multi-dimensional scaling and BIO-ENV procedure) of the physical and biological datasets from both areas determined that the geophysical variables, slope and gravel percentage, were the best predictors for megabenthos assemblage patterns. In conjunction with Geographic Information System (GIS) mod-els of the geomorphology and bathymetry, these geophysical variables were used to derive the spatial boundaries of ben-thic habitats for each study area. A hierarchical method of benthic-habitat mapping to the Secondary Biotope and Biological Facies levels was applied at the site (<10 km) scale. The combination of substrate type, sedimentary dynam-ics and physical processes related to near-seabed currents appear to be the dominant control on the benthic communi-ties in the northern Great Barrier Reef–Gulf of Papua region. These results add confidence to the use of geophysical data from seabed habitats, such as geology, sediment and morphology, as predictors for benthos distribution and thus provide a basis for marine reserve selection